GENETICS
Chromosome Structure and Function
a. Relate the structure and function of DNA, RNA (ribonucleic acid), and proteins to the concept of variation in organisms
DNA and RNA are a nucleic acid. The unit of structure and function in the nucleic acid is called a nucleotide. A nucleotide is composed of a phosphate group. A phosphate group is a 5-carbon sugar and protein base. The protein bases in nucleic acids are ring compounds. The four bases that makes up a DNA molecule are adenine (A), guanine (G), thymine (T), and cytosine (C). The four bases that make up the RNA molecule are adenine (A), guanine (G), cytosine (C), and uracil (U).
Most biological activities are carried out by proteins and thus it is important for the accurate synthesis of proteins. The genetic information that is required for protein synthesis is stored in DNA. The production of protein involves DNA, RNA, and proteins. The DNA holds the blueprint plan for protein production. The synthesis of protein begins with the messenger RNA (mRNA)- this function is to carry the genetic code for a particular amino acid, which is copied from the DNA in a series of three-base code "words". The transfer RNA is also formed by the DNA and is shaped so that it will pick up only one specific kind of amino acid. At the end of a tRNA is an anticodon and this is the site where it attaches to a mRNA codon. This codon is a triplet that specifies an amino acid base. Because there are 20 different animo acid molecules, then there are 20 different forms of tRNA molecules. Ribosomal RNA or rRNA is assembled by DNA. In the nucleolus, two subunits of rRNA will join with the ribosomal protein to form a ribosome. The ribosomes move out of the nucleolus and into the cytoplasm. Ribosomes are necessary for the synthesis of protein in that they catalyze the assembly of amino acids into protein chains.
The mRNA that is carrying the polypeptide code moves into the cytoplasm. The mRNA will attach itself to several ribosomes, each having its own ribosomal RNA. Specific tRNA molecules brings to the ribosomes their own kind of activated amino acid. The messenger RNA brings the genetic code for a polypeptide to the ribosome. The transfer RNA reads this code and the ribosome puts it all together.
Proteins function is based on its structure and shape. The structure and shape of a protein is determined by its sequence of amino acids.
b. Describe chromosome structure as a sequence of genes each with a specific locus
Within the nucleus of the non-dividing cell is a tangle of very fine threads. These threads are known as chromatin. When the chromatin threads come together, they shorten and thickening, forming chromosomes that can be seen quite well in the dividing cell.
Homologous chromosomes are chromosomes that have the same size and shape and they have the same genes on them. They are not identical. In humans, we inherit one from the mother and one from the father. They can have different alleles on them. Alleles are variants of the same gene that occur on the same place on a chromosome. A locus refers to the location on the chromosome where the gene is found.
DNA and RNA are a nucleic acid. The unit of structure and function in the nucleic acid is called a nucleotide. A nucleotide is composed of a phosphate group. A phosphate group is a 5-carbon sugar and protein base. The protein bases in nucleic acids are ring compounds. The four bases that makes up a DNA molecule are adenine (A), guanine (G), thymine (T), and cytosine (C). The four bases that make up the RNA molecule are adenine (A), guanine (G), cytosine (C), and uracil (U).
Most biological activities are carried out by proteins and thus it is important for the accurate synthesis of proteins. The genetic information that is required for protein synthesis is stored in DNA. The production of protein involves DNA, RNA, and proteins. The DNA holds the blueprint plan for protein production. The synthesis of protein begins with the messenger RNA (mRNA)- this function is to carry the genetic code for a particular amino acid, which is copied from the DNA in a series of three-base code "words". The transfer RNA is also formed by the DNA and is shaped so that it will pick up only one specific kind of amino acid. At the end of a tRNA is an anticodon and this is the site where it attaches to a mRNA codon. This codon is a triplet that specifies an amino acid base. Because there are 20 different animo acid molecules, then there are 20 different forms of tRNA molecules. Ribosomal RNA or rRNA is assembled by DNA. In the nucleolus, two subunits of rRNA will join with the ribosomal protein to form a ribosome. The ribosomes move out of the nucleolus and into the cytoplasm. Ribosomes are necessary for the synthesis of protein in that they catalyze the assembly of amino acids into protein chains.
The mRNA that is carrying the polypeptide code moves into the cytoplasm. The mRNA will attach itself to several ribosomes, each having its own ribosomal RNA. Specific tRNA molecules brings to the ribosomes their own kind of activated amino acid. The messenger RNA brings the genetic code for a polypeptide to the ribosome. The transfer RNA reads this code and the ribosome puts it all together.
Proteins function is based on its structure and shape. The structure and shape of a protein is determined by its sequence of amino acids.
b. Describe chromosome structure as a sequence of genes each with a specific locus
Within the nucleus of the non-dividing cell is a tangle of very fine threads. These threads are known as chromatin. When the chromatin threads come together, they shorten and thickening, forming chromosomes that can be seen quite well in the dividing cell.
Homologous chromosomes are chromosomes that have the same size and shape and they have the same genes on them. They are not identical. In humans, we inherit one from the mother and one from the father. They can have different alleles on them. Alleles are variants of the same gene that occur on the same place on a chromosome. A locus refers to the location on the chromosome where the gene is found.
Patterns of Inheritance
a. Explain the necessity of both meiosis and fertilization in promoting variation
Meiosis the the process of producing a viable egg and sperm cells. It reduces the number of chromosomes to one half in each gamete so that upon fertilization, the species chromosome number is kept constant. Each gamete contains genes that are different. During meiosis, the two chromosomes exchange small sections with each other, called recombination. This process creates new chromosomes. This is how meiosis is able to give us variations.
b. Describe the role of chromosomes in determining phenotypes (e.g., sex determination, chromosomal aberrations)
One set of chromosome comes from each parent. The genes found on the chromosomes determines the offspring's phenotype.
Mutations may occur and can be either good or bad.
Assuming the daughter cells receive the correct number of chromosomes, then problems arise in the structure of the DNA itself.
Some errors are not passed on to our children (such as changes that occur due to sun exposure), but other errors can occur in the DNA of cells that produce the eggs and sperm, called germline mutations and can be passed down.
If a child inherits a germline mutation, then every cell in their body will have this error in their DNA. This is responsible for hereditary diseases.
A gene is kind of a sentence that is made up of the bases A,T, G, and C that explains how to make a protein. There are various way to change this “sentence”:
1. Point Mutations- Changes in one base pair of a cell's DNA sequence. There are a few different types of point mutations.
a) Silent- no effect on the functioning of the protein. This is the least harmful.
b) Nonsense- Change in one DNA base pair. The altered DNA sequence interrupts the building of a protein. The result may cause a shortened protein that may or may not be functional.
c) Missense- changes a codon so that a different protein is created
Example:
Before: Max and Nan hit the can. (Each three letter “word” represents a codon)
After: Max and Fan hit the can.
2. Frame shift mutation- this occurs when one or more bases are inserted or deleted. Since our cells read in three letter “words”, adding or removing one “letter” changes each subsequent word, shifting the “letters” over. For example if we remove the x in the word Max, then all of the bases would shift over. The result would be a shortened protein, most likely non-functional.(Insertions, deletions, and duplications can all be frameshift mutations).
Before: Max and Nan hit the can.
After: Maa ndN anh itt hec an.
3. Deletion- a removal can be something small, such as removing 1 “word”, or longer deletions that affects large numbers of genes on the chromosome. Deletion can also cause frame shift mutation. The deleted DNA may alter the function a protein.
Before: Max and Nan hit the can.
After: Max and hit the can.
4. Insertion- this is an addition of one or more types of nucleotide base pairs in the DNA. Can cause frame shift mutation. This may result in a nonfunctional protein.
Before: Max and Nan hit the can.
After: Max and hub Nan hit the can.
5. Inversion- an entire section of the DNA is reversed. May be a few bases or a large region of the chromosome.
Before: Max and Nan hit the can.
After: Max and nac eht tih naN.
6. Duplication- A piece of DNA that is abnormally copied or more time times. This may affect the function of a protein.
DNA expression- this affects where and how much of a protein is made. Protein can be made at the wrong time or in the wrong cell types. This results in either too much or too little protein being made.
Chromosomal aberrations can occur if there is a change in the normal set of chromosomes, the changes in the individual chromosomes, or changes in the appearance of chromosomes through mutation-induced rearrangements. They can be associated with genetic diseases.
c. Predict the probable outcome of phenotypes in a genetic cross from the genotypes of the parents and mode of inheritance (e.g., autosomal or X-linked, dominant or recessive, codominance)
There are sets of coded instruction which make up the DNA molecules of a chromosome. Each gene is connected to a series of 250 “rungs” on the DNA “ladder”. Since the order of the rungs vary, each gene has a different code relating to one specific trait. The paired genes control the same characteristics and may give identical or different instructions.
Dominance- instructions given from one gene that overrides the recessive gene's. Example: a person with both genes for brown and green eyes will have brown eyes since the brown eye gene is dominant. If the dominant gene, D, for dark hair, then a person is heterozygous, Dd, for hair color (instructions from two genes are different).
Recessive Gene- failure of one gene (allele) to express itself in an observable manner. Even though the gene is present in the genotype, it is not observable in it's phenotype (organisms physical physical or biochemical characteristic). Example: Curly hair (dominant-C) and straight hair (recessive-c) both are present in a person's genotype. However, the person has straight hair. Recessive genes are always written in lower case.
Incomplete Dominance- one allele for a specific trait is not completely dominant of the other allele. The result is a combined phenotype. Example: Camelia flowers that have both red (dominant-A) and white (recessive-a) genes will produce a flower with pink petals.(heterozygot-Aa)
Codominance- pair of genes controlling the same characteristics give different instructions. Neither genes are dominant and both are represented in the result. Example: Human blood AB
Linked Genes- alleles inherited together. Genes physically close to one another on the same chromosome. Stay together during meiosis= genetically linked.
Sex-linked Genes- Genes located on one of the sex chromosomes. Since the x chromosome is longer, it contains genes not found on the Y chromosome. Therefore, most sex-linked genes are x-linked genes. Sex-linked genes do not have an allelic counterpart on the Y chromosome.
Purebred- produces offsprings with the same traits. The alleles are homozygous.
d. Explain the genetic and cellular bases for Mendel’s laws of dominance, segregation and independent assortment
The Law of Dominance: If two organisms exhibit contrasting traits are crossed, the trait that shows up in the first filial generation, F1, is the dominant trait. The recessive trait is hidden. Example: purebred tall pea plant is crossed with a short pea plant. All of their offspring will be tall, but not be pure tall. They will be hybrids. The phenotype of the first generation plants is tall. Mendel did not have the concept of the gene. Based on his observations, he concluded that two factors determine a characteristics and that two recessive factors must be needed in order for the characteristic to appear. He also determined that one dominant factor and one recessive factor will result in an offspring that has the dominant trait.
The Law of Segregation: When hybrids are crossed, the recessive trait segregates out at a ratio of three individuals with the dominant trait to one individual with the recessive trait. This 3:1 ratio is called phenotypic ratio- this one refers to the traits that can be seen. These hybrid crosses are also called F1 and their offsprings are called F2. The F2 generation produces another type of ratio called the genotype ratio- this one refers to the gene makeup. The genotype ratio is 1:2:1- 1 homozygous dominant (pure), 2 heterozygous (hybrid), and 1 homozygous (shows recessive trait).
The Law of Independent Assortment: Mendel believed that the allele pairs separate independently of the other alleles of the same gene.
Meiosis the the process of producing a viable egg and sperm cells. It reduces the number of chromosomes to one half in each gamete so that upon fertilization, the species chromosome number is kept constant. Each gamete contains genes that are different. During meiosis, the two chromosomes exchange small sections with each other, called recombination. This process creates new chromosomes. This is how meiosis is able to give us variations.
b. Describe the role of chromosomes in determining phenotypes (e.g., sex determination, chromosomal aberrations)
One set of chromosome comes from each parent. The genes found on the chromosomes determines the offspring's phenotype.
Mutations may occur and can be either good or bad.
Assuming the daughter cells receive the correct number of chromosomes, then problems arise in the structure of the DNA itself.
Some errors are not passed on to our children (such as changes that occur due to sun exposure), but other errors can occur in the DNA of cells that produce the eggs and sperm, called germline mutations and can be passed down.
If a child inherits a germline mutation, then every cell in their body will have this error in their DNA. This is responsible for hereditary diseases.
A gene is kind of a sentence that is made up of the bases A,T, G, and C that explains how to make a protein. There are various way to change this “sentence”:
1. Point Mutations- Changes in one base pair of a cell's DNA sequence. There are a few different types of point mutations.
a) Silent- no effect on the functioning of the protein. This is the least harmful.
b) Nonsense- Change in one DNA base pair. The altered DNA sequence interrupts the building of a protein. The result may cause a shortened protein that may or may not be functional.
c) Missense- changes a codon so that a different protein is created
Example:
Before: Max and Nan hit the can. (Each three letter “word” represents a codon)
After: Max and Fan hit the can.
2. Frame shift mutation- this occurs when one or more bases are inserted or deleted. Since our cells read in three letter “words”, adding or removing one “letter” changes each subsequent word, shifting the “letters” over. For example if we remove the x in the word Max, then all of the bases would shift over. The result would be a shortened protein, most likely non-functional.(Insertions, deletions, and duplications can all be frameshift mutations).
Before: Max and Nan hit the can.
After: Maa ndN anh itt hec an.
3. Deletion- a removal can be something small, such as removing 1 “word”, or longer deletions that affects large numbers of genes on the chromosome. Deletion can also cause frame shift mutation. The deleted DNA may alter the function a protein.
Before: Max and Nan hit the can.
After: Max and hit the can.
4. Insertion- this is an addition of one or more types of nucleotide base pairs in the DNA. Can cause frame shift mutation. This may result in a nonfunctional protein.
Before: Max and Nan hit the can.
After: Max and hub Nan hit the can.
5. Inversion- an entire section of the DNA is reversed. May be a few bases or a large region of the chromosome.
Before: Max and Nan hit the can.
After: Max and nac eht tih naN.
6. Duplication- A piece of DNA that is abnormally copied or more time times. This may affect the function of a protein.
DNA expression- this affects where and how much of a protein is made. Protein can be made at the wrong time or in the wrong cell types. This results in either too much or too little protein being made.
Chromosomal aberrations can occur if there is a change in the normal set of chromosomes, the changes in the individual chromosomes, or changes in the appearance of chromosomes through mutation-induced rearrangements. They can be associated with genetic diseases.
c. Predict the probable outcome of phenotypes in a genetic cross from the genotypes of the parents and mode of inheritance (e.g., autosomal or X-linked, dominant or recessive, codominance)
There are sets of coded instruction which make up the DNA molecules of a chromosome. Each gene is connected to a series of 250 “rungs” on the DNA “ladder”. Since the order of the rungs vary, each gene has a different code relating to one specific trait. The paired genes control the same characteristics and may give identical or different instructions.
Dominance- instructions given from one gene that overrides the recessive gene's. Example: a person with both genes for brown and green eyes will have brown eyes since the brown eye gene is dominant. If the dominant gene, D, for dark hair, then a person is heterozygous, Dd, for hair color (instructions from two genes are different).
Recessive Gene- failure of one gene (allele) to express itself in an observable manner. Even though the gene is present in the genotype, it is not observable in it's phenotype (organisms physical physical or biochemical characteristic). Example: Curly hair (dominant-C) and straight hair (recessive-c) both are present in a person's genotype. However, the person has straight hair. Recessive genes are always written in lower case.
Incomplete Dominance- one allele for a specific trait is not completely dominant of the other allele. The result is a combined phenotype. Example: Camelia flowers that have both red (dominant-A) and white (recessive-a) genes will produce a flower with pink petals.(heterozygot-Aa)
Codominance- pair of genes controlling the same characteristics give different instructions. Neither genes are dominant and both are represented in the result. Example: Human blood AB
Linked Genes- alleles inherited together. Genes physically close to one another on the same chromosome. Stay together during meiosis= genetically linked.
Sex-linked Genes- Genes located on one of the sex chromosomes. Since the x chromosome is longer, it contains genes not found on the Y chromosome. Therefore, most sex-linked genes are x-linked genes. Sex-linked genes do not have an allelic counterpart on the Y chromosome.
Purebred- produces offsprings with the same traits. The alleles are homozygous.
d. Explain the genetic and cellular bases for Mendel’s laws of dominance, segregation and independent assortment
The Law of Dominance: If two organisms exhibit contrasting traits are crossed, the trait that shows up in the first filial generation, F1, is the dominant trait. The recessive trait is hidden. Example: purebred tall pea plant is crossed with a short pea plant. All of their offspring will be tall, but not be pure tall. They will be hybrids. The phenotype of the first generation plants is tall. Mendel did not have the concept of the gene. Based on his observations, he concluded that two factors determine a characteristics and that two recessive factors must be needed in order for the characteristic to appear. He also determined that one dominant factor and one recessive factor will result in an offspring that has the dominant trait.
The Law of Segregation: When hybrids are crossed, the recessive trait segregates out at a ratio of three individuals with the dominant trait to one individual with the recessive trait. This 3:1 ratio is called phenotypic ratio- this one refers to the traits that can be seen. These hybrid crosses are also called F1 and their offsprings are called F2. The F2 generation produces another type of ratio called the genotype ratio- this one refers to the gene makeup. The genotype ratio is 1:2:1- 1 homozygous dominant (pure), 2 heterozygous (hybrid), and 1 homozygous (shows recessive trait).
The Law of Independent Assortment: Mendel believed that the allele pairs separate independently of the other alleles of the same gene.
Gene Expression
a. Explain how random chromosome segregation explains the probability that a particular allele will be in a gamete
Meiosis involves chromosomes to randomly segregate. This accounts for the probability that a certain allele will be packaged in any gamete.
b. Recognize that specialization of cells in multicellular organisms is usually due to different patterns of gene expression rather than to differences among the genes themselves
There are clever mechanisms that turn genes off and on so that they only function where there is a need for their service. In prokaryotes, since they are sensitive to their environment, their genetic activity is controlled by certain proteins that interact directly with the DNA to quickly adjust to changes in the environment. Genetic expression is the process where genotypes coded in the genes are exhibited by the phenotypes of the individuals. As we have learned earlier, the DNA is copied by the RNA which is then synthesized into protein. Some proteins are made by almost every cell and some proteins are made by only one type of cells. So, if all cells have the same genes, then why do they not make the same proteins? In each cell, some genes are active (expressed) while others are turned off (repressed). The regulation of the gene expression is most likely to occur during the process of transcription. For prokaryotes, the setting is set to allow for continual synthesis of protein. In Eukaryotes, this system is normally turned off until activated.
Unlike prokaryotes, eukaryotes' gene-regulating mechanism operate in the nucleus before before and after RNA transcription, and in the cytoplasm both before and after translation.
Packed tightly in the DNA are these proteins called histones. These histones are packed in a manner that prevents the RNA polymerase from transcribing the DNA. The control of protein synthesis is regulated by the genes that controls the packing density of the histones. X-chromosomes inactivation is when the dense packing of the X chromosome in females prevents its function even in interphase. This inactivation is inherited and begins during embryonic development, where one of the X chromosomes is randomly packed, making it inactive for life. Activator-enhancer complex is unique in eukaryotes. They normally have to be activated in order to begin protein synthesis, which requires the use of transcription factors and RNA polymerase. The general process of protein synthesis in eukaryotes involves the following steps:
1) activators (a special type of transcription factor) binds to enhancers (discrete DNA units located at points along the chromosomes)
2) activator-enhancer complex bends the DNA molecule so that additional transcription factors are better able to access the bonding sites
3) bonding of additional transcription factors to the operator allows greater access by the RNA polymease- this begins the transcription process
4) silencers (repressor protein) blocks the transcription at this point by bonding with DNA nucleotide sequences
The processing and packaging of RNA both in the nucleus and in the cytoplasm provides two more opportunities for gene regulation to occur after transcription, but before translation.
c. Describe how alleles that are lethal in a homozygous individual may be carried in a heterozygote and thus maintained in a gene pool
The two parings that can occur in the genotype are homozygous (paring of two same alleles, whether it be dominant, codominant, or recessive) and heterozygous (pairing of two different alleles). Recessive lethal alleles, when expressed, causes the death of an organism. These arise when there is a mutation to a normal allele that disrupts the function of an essential gene. And, without this essential gene, the organism will not be able to survive. Tay-Sachs Disease is a type of genetic disorder that results from the inheritance of two recessive genes that causes a malfunction of the nervous system where the nerve cells are destroyed. The disorder greatly shortens a life span and it is rare for afflicted children to live past the age of 6. Lethal alleles can be dominant or recessive and can be sex-linked or autosomal. If the allele is dominant, then both homozygous dominant and heterozygous organisms will not survive. If it is a recessive allele, then only a homozygous recessive organism will die. Healthy heterozygous organisms will contribute the masked recessive gene to the gene pool, which allows the gene to be maintained.
d. Distinguish when and why mutations in the DNA sequence of a gene may or may not affect the expression of the gene or the sequence of amino acids in an encoded protein
I copied and pasted the information from one of the secions above here.
One set of chromosome comes from each parent. The genes found on the chromosomes determines the offspring's phenotype.
Mutations may occur and can be either good or bad.
Assuming the daughter cells receive the correct number of chromosomes, then problems arise in the structure of the DNA itself.
Some errors are not passed on to our children (such as changes that occur due to sun exposure), but other errors can occur in the DNA of cells that produce the eggs and sperm, called germline mutations and can be passed down.
If a child inherits a germline mutation, then every cell in their body will have this error in their DNA. This is responsible for hereditary diseases.
A gene is kind of a sentence that is made up of the bases A,T, G, and C that explains how to make a protein. There are various way to change this “sentence”:
1. Point Mutations- Changes in one base pair of a cell's DNA sequence. There are a few different types of point mutations.
a) Silent- no effect on the functioning of the protein. This is the least harmful.
b) Nonsense- Change in one DNA base pair. The altered DNA sequence interrupts the building of a protein. The result may cause a shortened protein that may or may not be functional.
c) Missense- changes a codon so that a different protein is created
Example:
Before: Max and Nan hit the can. (Each three letter “word” represents a codon)
After: Max and Fan hit the can.
2. Frame shift mutation- this occurs when one or more bases are inserted or deleted. Since our cells read in three letter “words”, adding or removing one “letter” changes each subsequent word, shifting the “letters” over. For example if we remove the x in the word Max, then all of the bases would shift over. The result would be a shortened protein, most likely non-functional.(Insertions, deletions, and duplications can all be frameshift mutations).
Before: Max and Nan hit the can.
After: Maa ndN anh itt hec an.
3. Deletion- a removal can be something small, such as removing 1 “word”, or longer deletions that affects large numbers of genes on the chromosome. Deletion can also cause frame shift mutation. The deleted DNA may alter the function a protein.
Before: Max and Nan hit the can.
After: Max and hit the can.
4. Insertion- this is an addition of one or more types of nucleotide base pairs in the DNA. Can cause frame shift mutation. This may result in a nonfunctional protein.
Before: Max and Nan hit the can.
After: Max and hub Nan hit the can.
5. Inversion- an entire section of the DNA is reversed. May be a few bases or a large region of the chromosome.
Before: Max and Nan hit the can.
After: Max and nac eht tih naN.
6. Duplication- A piece of DNA that is abnormally copied or more time times. This may affect the function of a protein.
DNA expression- this affects where and how much of a protein is made. Protein can be made at the wrong time or in the wrong cell types. This results in either too much or too little protein being made.
Chromosomal aberrations can occur if there is a change in the normal set of chromosomes, the changes in the individual chromosomes, or changes in the appearance of chromosomes through mutation-induced rearrangements. They can be associated with genetic diseases.
Meiosis involves chromosomes to randomly segregate. This accounts for the probability that a certain allele will be packaged in any gamete.
b. Recognize that specialization of cells in multicellular organisms is usually due to different patterns of gene expression rather than to differences among the genes themselves
There are clever mechanisms that turn genes off and on so that they only function where there is a need for their service. In prokaryotes, since they are sensitive to their environment, their genetic activity is controlled by certain proteins that interact directly with the DNA to quickly adjust to changes in the environment. Genetic expression is the process where genotypes coded in the genes are exhibited by the phenotypes of the individuals. As we have learned earlier, the DNA is copied by the RNA which is then synthesized into protein. Some proteins are made by almost every cell and some proteins are made by only one type of cells. So, if all cells have the same genes, then why do they not make the same proteins? In each cell, some genes are active (expressed) while others are turned off (repressed). The regulation of the gene expression is most likely to occur during the process of transcription. For prokaryotes, the setting is set to allow for continual synthesis of protein. In Eukaryotes, this system is normally turned off until activated.
Unlike prokaryotes, eukaryotes' gene-regulating mechanism operate in the nucleus before before and after RNA transcription, and in the cytoplasm both before and after translation.
Packed tightly in the DNA are these proteins called histones. These histones are packed in a manner that prevents the RNA polymerase from transcribing the DNA. The control of protein synthesis is regulated by the genes that controls the packing density of the histones. X-chromosomes inactivation is when the dense packing of the X chromosome in females prevents its function even in interphase. This inactivation is inherited and begins during embryonic development, where one of the X chromosomes is randomly packed, making it inactive for life. Activator-enhancer complex is unique in eukaryotes. They normally have to be activated in order to begin protein synthesis, which requires the use of transcription factors and RNA polymerase. The general process of protein synthesis in eukaryotes involves the following steps:
1) activators (a special type of transcription factor) binds to enhancers (discrete DNA units located at points along the chromosomes)
2) activator-enhancer complex bends the DNA molecule so that additional transcription factors are better able to access the bonding sites
3) bonding of additional transcription factors to the operator allows greater access by the RNA polymease- this begins the transcription process
4) silencers (repressor protein) blocks the transcription at this point by bonding with DNA nucleotide sequences
The processing and packaging of RNA both in the nucleus and in the cytoplasm provides two more opportunities for gene regulation to occur after transcription, but before translation.
c. Describe how alleles that are lethal in a homozygous individual may be carried in a heterozygote and thus maintained in a gene pool
The two parings that can occur in the genotype are homozygous (paring of two same alleles, whether it be dominant, codominant, or recessive) and heterozygous (pairing of two different alleles). Recessive lethal alleles, when expressed, causes the death of an organism. These arise when there is a mutation to a normal allele that disrupts the function of an essential gene. And, without this essential gene, the organism will not be able to survive. Tay-Sachs Disease is a type of genetic disorder that results from the inheritance of two recessive genes that causes a malfunction of the nervous system where the nerve cells are destroyed. The disorder greatly shortens a life span and it is rare for afflicted children to live past the age of 6. Lethal alleles can be dominant or recessive and can be sex-linked or autosomal. If the allele is dominant, then both homozygous dominant and heterozygous organisms will not survive. If it is a recessive allele, then only a homozygous recessive organism will die. Healthy heterozygous organisms will contribute the masked recessive gene to the gene pool, which allows the gene to be maintained.
d. Distinguish when and why mutations in the DNA sequence of a gene may or may not affect the expression of the gene or the sequence of amino acids in an encoded protein
I copied and pasted the information from one of the secions above here.
One set of chromosome comes from each parent. The genes found on the chromosomes determines the offspring's phenotype.
Mutations may occur and can be either good or bad.
Assuming the daughter cells receive the correct number of chromosomes, then problems arise in the structure of the DNA itself.
Some errors are not passed on to our children (such as changes that occur due to sun exposure), but other errors can occur in the DNA of cells that produce the eggs and sperm, called germline mutations and can be passed down.
If a child inherits a germline mutation, then every cell in their body will have this error in their DNA. This is responsible for hereditary diseases.
A gene is kind of a sentence that is made up of the bases A,T, G, and C that explains how to make a protein. There are various way to change this “sentence”:
1. Point Mutations- Changes in one base pair of a cell's DNA sequence. There are a few different types of point mutations.
a) Silent- no effect on the functioning of the protein. This is the least harmful.
b) Nonsense- Change in one DNA base pair. The altered DNA sequence interrupts the building of a protein. The result may cause a shortened protein that may or may not be functional.
c) Missense- changes a codon so that a different protein is created
Example:
Before: Max and Nan hit the can. (Each three letter “word” represents a codon)
After: Max and Fan hit the can.
2. Frame shift mutation- this occurs when one or more bases are inserted or deleted. Since our cells read in three letter “words”, adding or removing one “letter” changes each subsequent word, shifting the “letters” over. For example if we remove the x in the word Max, then all of the bases would shift over. The result would be a shortened protein, most likely non-functional.(Insertions, deletions, and duplications can all be frameshift mutations).
Before: Max and Nan hit the can.
After: Maa ndN anh itt hec an.
3. Deletion- a removal can be something small, such as removing 1 “word”, or longer deletions that affects large numbers of genes on the chromosome. Deletion can also cause frame shift mutation. The deleted DNA may alter the function a protein.
Before: Max and Nan hit the can.
After: Max and hit the can.
4. Insertion- this is an addition of one or more types of nucleotide base pairs in the DNA. Can cause frame shift mutation. This may result in a nonfunctional protein.
Before: Max and Nan hit the can.
After: Max and hub Nan hit the can.
5. Inversion- an entire section of the DNA is reversed. May be a few bases or a large region of the chromosome.
Before: Max and Nan hit the can.
After: Max and nac eht tih naN.
6. Duplication- A piece of DNA that is abnormally copied or more time times. This may affect the function of a protein.
DNA expression- this affects where and how much of a protein is made. Protein can be made at the wrong time or in the wrong cell types. This results in either too much or too little protein being made.
Chromosomal aberrations can occur if there is a change in the normal set of chromosomes, the changes in the individual chromosomes, or changes in the appearance of chromosomes through mutation-induced rearrangements. They can be associated with genetic diseases.
Biotechnology
a. Recognize how genetic engineering (biotechnology) produces biomedical and agricultural products
Scientists have found it possible through biotechnology of genetic engineering to transfer the genetic information from one organism into another.
Crops have been a focus of biotechnology as efforts have been made to improve the quantity and profitability by improving a crops resistance to insects and herbicides as well as delaying ripening to prevent spoilage during transport. The creations of transgenic plant, receives genes from another organism, has proved to be more difficult to do than animals. Creating a crop that is resistant to a certain herbicide has been more of a success. Researchers have discovered a herbicide-resistance bacteria and isolated the genes responsible for this condition and injected them into the plant. This then proved to be resistant to that herbicide.
Transgenic animals model an advancement in DNA technology. A healthy egg is removed from a female and fertilized in a laboratory. The desired gene is identified, isolated and cloned. The cloned genes are injected directly into the eggs which are then implanted into a host female. The hope is that this process will provide a cheap, fast means of generating the desired enzymes and proteins as well as increasing the production of meat and other animal products.
b. Describe the construction of recombinant DNA molecules by basic DNA technology including restriction digestion by endonucleases, gel electrophoresis, ligation, and transformation
Through gene splicing, geneticist are able to remove a specific gene from the cells of a human and splice it with the DNA strand from a bacterium.
Transduction: spliced strand of DNA can be introduced into a bacteria cell. The bacterium will reproduce clones. The spliced ring of DNA is now recombinant DNA- bearing a human gene and bacterial genes.
Endonuclease: enzymes that cuts DNA into fragments
Gel electrophoresis: allows you to sort and measure the DNA strands by filtering the DNA strands using an electrical current
Ligation: joining DNA fragments together with covalent bonds using the enzyme ligase
Transformation: this is the introduction of a foreign DNA properties of the organism, when recombinant DNA is introduced into recipient cells
Scientists have found it possible through biotechnology of genetic engineering to transfer the genetic information from one organism into another.
Crops have been a focus of biotechnology as efforts have been made to improve the quantity and profitability by improving a crops resistance to insects and herbicides as well as delaying ripening to prevent spoilage during transport. The creations of transgenic plant, receives genes from another organism, has proved to be more difficult to do than animals. Creating a crop that is resistant to a certain herbicide has been more of a success. Researchers have discovered a herbicide-resistance bacteria and isolated the genes responsible for this condition and injected them into the plant. This then proved to be resistant to that herbicide.
Transgenic animals model an advancement in DNA technology. A healthy egg is removed from a female and fertilized in a laboratory. The desired gene is identified, isolated and cloned. The cloned genes are injected directly into the eggs which are then implanted into a host female. The hope is that this process will provide a cheap, fast means of generating the desired enzymes and proteins as well as increasing the production of meat and other animal products.
b. Describe the construction of recombinant DNA molecules by basic DNA technology including restriction digestion by endonucleases, gel electrophoresis, ligation, and transformation
Through gene splicing, geneticist are able to remove a specific gene from the cells of a human and splice it with the DNA strand from a bacterium.
Transduction: spliced strand of DNA can be introduced into a bacteria cell. The bacterium will reproduce clones. The spliced ring of DNA is now recombinant DNA- bearing a human gene and bacterial genes.
Endonuclease: enzymes that cuts DNA into fragments
Gel electrophoresis: allows you to sort and measure the DNA strands by filtering the DNA strands using an electrical current
Ligation: joining DNA fragments together with covalent bonds using the enzyme ligase
Transformation: this is the introduction of a foreign DNA properties of the organism, when recombinant DNA is introduced into recipient cells
Bioethics
a. Discuss issues of bioethics including genetic engineering, cloning, the human genome project, gene therapy, and medical implications
Legal and ethical challenges poses many questions such as:
Do we have the right to alter a person's genes?
Do we have the right to control the genetic complement of the human population?
Who has the right to the cure?
Considerations include:
genetic diversity through the development of new gene combinations, which normally have positive effect, but may also have unintended unforeseen consequences
creating new genes may also create a new pathogen for which we have no cures
do we have the ability to safely handle genetically altered organisms?
there is a big controversy over the safety of GMOs, are they safe for consumption? do they harm the environment?
privacy issues
legal issues
Legal and ethical challenges poses many questions such as:
Do we have the right to alter a person's genes?
Do we have the right to control the genetic complement of the human population?
Who has the right to the cure?
Considerations include:
genetic diversity through the development of new gene combinations, which normally have positive effect, but may also have unintended unforeseen consequences
creating new genes may also create a new pathogen for which we have no cures
do we have the ability to safely handle genetically altered organisms?
there is a big controversy over the safety of GMOs, are they safe for consumption? do they harm the environment?
privacy issues
legal issues
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