DNA and mutations
nucleotide excision repair
(removal of errors and replacement of up to 30 nucleotides)
Frame shift mutation
- A change that alters the reading frame of codons; insertion or deletion not in multiples of 3 nucleotides.
Conditional mutation
- A mutation that affects the phenotype only under certain conditions. Ex: Hemolytic anemia occurring only in the presence of fava beans or antimalarial drugs.
Splice site mutation
- A point mutation that alters a site where introns are normally removed from the mRNA. This mutation may cause introns to be retained and translated, or exons to not be translated.
Insertion
- Addition of DNA; this type of mutation can also offset a gene's codon reading frame unless it is addition in multiples of 3 nucleotides.
Quaternary
- Interactions between 2 or more separate polypeptides
Tertiary
- Interactions between distant amino acids in response to attraction or repulsion of water molecules (hydrophobic and hydrophilic interactions)
Deletion
- Removal of DNA; this type of mutation can offset a gene's codon reading frame unless it is removal in multiples of 3 nucleotides.
Only about _____ of human DNA codes for proteins. The remaining _____ includes viral DNA (remnants of DNA that originated from viral infections in our ancestors), noncoding RNAs (including pseudogenes, which can be transcribed, but cannot be translated into a protein), repetitive sequences (such as Alu repeat sequences), introns, promoters and other control sequences, small interfering RNAs (siRNA) and micro RNAs (miRNA).
1.5% 98.5%
Below is a nucleotide sequence of a single strand of DNA. Write the sequence of the Complementary strand indicating the appropriate 5' and 3' ends. 5'-A-T-C-A-C-T-A-T-A-T-A-G-C-T-C-G-A-T-C-G-T-C-A-T-C-G-3'
5'-A-T-C-A-C-T-A-T-A-T-A-G-C-T-C-G-A-T-C-G-T-C-A-T-C-G-3' 3'-T-A-G-T-G-A-T-A-T-A-T-C-G-A-G-C-T-A-G-C-A-G-T-A-G-C-5'
Based on the following mRNA sequence, what is the amino acid sequence? (You will need to use the Genetic code on page 186) 5'-AUGGGGCUGUUGAGCUGA-3'
5'-AUGGGGCUGUUGAGCUGA-3' Start (Methionine)-Glycine-Leucine-Leucine-Serine-Stop
About ______ of all genes in the human genome are alternatively spliced.
90%
spontaneous mutation rate for autosomal genes can be estimated
= # of cases/(2*# of individuals examined)
Given the percentage of the nucleotides below, determine the percentage of all the other nucleotides. a. A - 6% → A = 6%, T = ?, C = ?, G = ? b. C - 12% → C = 12%, G = ?, A = ?, T = ? c. G - 23.12% → G = 23.12%, C = ?, A = ?, T = ?
A = T and C = G; and A + T + G + C = 100% a. A - 6% → A = 6%, T = 6%, C = 44%, G = 44% b. C - 12% → C = 12%, G = 12%, A = 38%, T = 38% c. G - 23.12% → G = 23.12%, C = 23.12%, A = 26.88%, T = 26.88%
What happens during translation? Where in the cell does translation occur?
A finished mRNA strand will leave the nucleus to be translated into protein by ribosomes in the cytoplasm or by ribosomes bound to the rough Endoplasmic reticulum. Each codon is translated into its appropriate amino acid through the aid of the tRNA. These amino acids are joined together by peptide bonds to create polypeptides.
____ is an agent that causes genetic mutation.
A mutagen
What is a mutagen? What are some examples?
A mutagen is an agent that causes genetic mutation. Examples include certain chemicals, such as those found in cigarette smoke, and radiation. We are naturally exposed to radiation in the form of cosmic rays, sunlight and radioactive minerals in the earth's crust.
What is a mutation? How does a mutation differ from a polymorphism?
A mutation is a change in the sequence of DNA that is present in less than 1% of the population. A polymorphism is a mutation that is present in more than 1% of the population.
When might a mutation stay in a population? When might a mutation be selected out of a population?
A mutation will likely stay in a population if it causes increased survival or reproductive success, or if it at least does not decrease survival or reproductive success. A mutation will likely be selected out of a population if it decreases survival or reproductive success.
What is a nucleotide?
A nucleotide is comprised of a phosphate group, a 5-carbon sugar, and a nitrogenous base. DNA has 4 types of nitrogenous bases - adenine (A), thymine (T), guanine (G) and cytosine (C). Nucleotides are the building blocks of DNA and RNA.
Nonsense mutation
A point mutation that results in a "stop" codon. UAA UAG UGA
Missense mutation -
A point mutation that results in an amino acid change. CHANGES A CODON THAT NORMALLY SPECIFIES A PARTICULAR AMINO ACID INTO ONE THAT CODES FOR A DIFFERENT AMINO ACID. EX: Sickle cell anemia--nonsynonomous codon
______ groups promote unwinding and subsequent transcription of DNA in certain places
Acetyl and phosphate
_______ change occurs when non-DNA chemical groups are added to genes to either stimulate or depress their expression. In this way, gene expression is altered without changing the DNA sequence itself.
An epigenetic
What is an epigenetic change?
An epigenetic change occurs when non-DNA chemical groups are added to genes to either stimulate or depress their expression. In this way, gene expression is altered without changing the DNA sequence itself. An example of an epigenetic change would be the addition of acetyl groups to histones that wrap DNA of a certain gene. Although the acetyl groups are not DNA (they are "outside the gene"), they can affect expression of that gene by causing it to become expressed - they turn the gene "on". Epigenetic changes can be inherited (passed down from generation to generation).
What do we mean when we say that DNA is antiparallel?
Antiparallel means that the two stands of DNA run opposite of one another - one strand is oriented one way and the other strand is oriented the opposite way.
(replacement of one to five nucleotides and removal or errors mainly caused by oxidative damage).
Base excision repair
How can a gene code for more than one protein?
Before leaving the nucleus, mRNA will remove introns and splice together the remaining exons. Exons can be spliced together in different orders and combinations. This is known as alternative splicing and this process increases the number of possible proteins that can be produced by the genome. About 90% of all genes in the human genome are alternatively spliced. Additionally, introns in a template strand may code for proteins in a coding strand, also increasing the numbers of proteins that can be produced.
What did Watson and Crick determine from Franklin's Photograph 51 and Chargaff's findings that the amount of T equals the amount of A and the amount of C equals the amount of G? Which of the bases are purines, which are pyrimidines?
COMPLEMENTARY BASE PAIRS T=A G=C A&G=purines--2 rings CUT=pyrimidines--1 ring Having complementary base pairs that include a 1-ring structure and a 2-ring structure ensure that the width of the double helix remains uniform throughout.
Which type of proteins aid in protein folding? What happens when proteins are misfolded?
Chaperone proteins aid in protein folding. If proteins are misfolded, they may be corrected or they may be digested and recycled by a proteasome.
What did Watson and Crick determine from Franklin's Photograph 51 and Chargaff's findings that the amount of T equals the amount of A and the amount of C equals the amount of G? Which of the bases are purines, which are pyrimidines?
Chargaff originally found that the number of thymine (T) bases was equal to the number of adenine (A) bases, and the number of guanine (G) bases was equal to the number of cytosine (C) bases. Watson and Crick used this information to determine that A and T were complementary bases pairs and C and G were complementary base pairs. A and G are purines (2 rings) and T and C are pyrimidines (1 ring). Having complementary base pairs that include a 1-ring structure and a 2-ring structure ensure that the width of the double helix remains uniform throughout.
_____ is composed of DNA wound around proteins called histones.
Chromatin
What is chromatin remodeling? How does chromatin remodeling control transcription?
Chromatin is composed of DNA wound around proteins called histones. Before DNA can be transcribed, it must first be unwound and exposed to the RNA polymerase and RNA nucleotides. Certain groups can be added or removed from histones to either allow or prevent the DNA in certain areas in the chromatin from unwinding. These groups include methyl groups, acetyl groups and phosphate groups. Acetyl and phosphate groups promote unwinding and subsequent transcription of DNA in certain places, and methyl groups prevent unwinding, and thus prevent transcription of certain genes.
Explain how codons are triplet, nonoverlapping and universal?
Codons consist of 3 nucleotides (triplet), each nucleotide belongs to only one codon (nonoverlapping), and all organisms (with very few exceptions) use the same mRNA-amino acid translation language (universal).
- A mutation that affects the phenotype only under certain conditions. Ex: Hemolytic anemia occurring only in the presence of fava beans or antimalarial drugs.
Conditional mutation
= enzyme that adds DNA nucleotides to the complementary base of the template strand to form a new strand of DNA (continuous on the 3'-5' strand but discontinuous on the 5'-3' strand because it can only add nucleotides to the 3'-carbon of the previous nucleotide) THEREFORE THE NEW STRAND IS BUILT 5->3
DNA Polymerase
Nuclear DNA may be repaired during DNA replication by______
DNA polymerase and other proteins.
How and why do mutations occur so commonly in DNA repeats? What is a palindrome? How might an insertion or deletion occur due to DNA repeats?
DNA repeats, or hot spots, are places where a short DNA sequence is repeated over and over. In these places, the replication enzymes may become "confused," and the repeat may pair with another complementary repeated section of the DNA during DNA replication, causing a loop in the DNA strand. Additionally, enzymes may become confused by palindromes, which are places where the sequence reads the same in the 3'-5' in both strands.
- Removal of DNA; this type of mutation can offset a gene's codon reading frame unless it is removal in multiples of 3 nucleotides.
Deletion
What do we mean when we say that DNA is semi-conservative?
During DNA replication, the two strands of the double helix will come apart and each strand serves as a template for a new double helix. Each new resulting double helix contains one original strand (conservation of the original molecule) and one new strand, making it semi-conservative.
Why might the phenotypic effects of a mutation become more severe over generations (such as in Myotonic dystrophy)?
EXPANDING TRIPLET REPEAT; Triplet repeats that increase the occurrence and affects of mutation can grow within the genome
How is the mRNA sequence altered before it leaves the nucleus?
First, a methylated cap is added to the 5' end a poly A tail is added to the 3' end of the mRNA molecule to aid in the initiation of protein synthesis. Then introns are removed (parts of the gene that will not be used to make the protein) and the remaining exon pieces are spliced together to make a single strand of mRNA. Splicing together the exons in differing orders and combinations allows for many different isoform proteins.
- A change that alters the reading frame of codons; insertion or deletion not in multiples of 3 nucleotides.
Frame shift mutation
_____ occur during DNA replication just prior to meiosis, which is the formation of gametes. Mutations in gametes, or germ cells, will affect every cell in the resulting individual following fertilization with another gamete.
Germline mutations
What is the difference between germline and somatic mutations?
Germline mutations occur during DNA replication just prior to meiosis, which is the formation of gametes. Mutations in gametes, or germ cells, will affect every cell in the resulting individual following fertilization with another gamete. Somatic mutations occur during DNA replication just prior to mitosis, which is the formation of somatic cells. Only descendent cells of this mutated somatic cell will be affected instead of all cells in the individual.
= enzyme that unwinds the parental double helix
Helicase
What are the functions of helicase, primase, DNA polymerase, and ligase. What are Okazaki fragments?
Helicase = enzyme that unwinds the parental double helix Primase = enzyme that adds a short RNA primer on each DNA template strand DNA Polymerase = enzyme that adds DNA nucleotides to the complementary base of the template strand to form a new strand of DNA (continuous on the 3'-5' strand but discontinuous on the 5'-3' strand because it can only add nucleotides to the 3'-carbon of the previous nucleotide) Ligase = enzyme that joins together Okazaki fragments (fragments of DNA due to discontinuous adding of nucleotides on the 5'-3' strand).
How do the specific subunits of hemoglobin change as the embryo develops into a fetus and then later as an adult?
Hemoglobin is a large protein complex composed of four polypeptide chains. Hemoglobin structure changes depending on oxygen concentration in the body and whether oxygen is acquired from the placenta or directly through the individual's lungs. As an embryo, hemoglobin is composed of two epsilon and two zeta chains. As a fetus, hemoglobin is composed of gamma and alpha chains, and as an adult, hemoglobin is composed of alpha and beta chains. The genes that code for these hemoglobin proteins are turned on and off during certain phases of the individual's development via epigenetic changes.
What happens during transcription? Where in the cell does transcription occur?
In transcription, RNA polymerase is used to create a strand of RNA that is complementary to a template strand of DNA. Thus, the genetic information from DNA is copied into an RNA form. This process occurs in the nucleus.
- Addition of DNA; this type of mutation can also offset a gene's codon reading frame unless it is addition in multiples of 3 nucleotides.
Insertion
Secondary -
Interactions between nearby amino acids that cause shapes such as an alpha helix and a beta-pleated sheet within the polypeptide
= enzyme that joins together Okazaki fragments (fragments of DNA due to discontinuous adding of nucleotides on the 5'-3' strand).
Ligase
Describe the three types of RNA.
Messanger RNA (mRNA) is the strand of RNA created from the transcription of the DNA template. This RNA contains information for making a specific protein. The mRNA strand is read in groups of 3 nucleotides, known as a codon. Each codon translates into a specific amino acid.Ribosomal RNA (rRNA) joins with other proteins to form ribosomes. Ribosomes function to make proteins based on the information in a strand of mRNA. Transfer RNA (tRNA) is a clover-leaf shaped structure which has an anticodon on one end (will bind to a matching codon of mRNA) and the corresponding amino acid on the other end. tRNA serves as the translator during the process of translation.
How might a mutation in the region of the genome that encodes micro RNA (miRNA) affect protein production?
Micro RNAs impede translation of certain genes by binding to the initial control region of mRNA. If there is a mutation in the region of the genome that encodes a micro RNA, then the genes that would have been suppressed by that micro RNA will be free to be expressed by translation into a protein.
____= A point mutation that results in an amino acid change.
Missense mutation
Why do mitochondrial genes have a higher rate of mutation than nuclear genes?
Mitochondrial DNA cannot self-repair, unlike nuclear DNA, which can self-repair.
What are some practical applications of mutagens in genetic research? Can mutagens cause specific mutations?
Mutagens may be used to determine gene function. However, the site of mutation usually cannot be controlled. Site-directed mutation is mass production of mutated genes, which can then be inserted into the genome. A MUTAGEN CANNOT CAUSE A SPECIFIC MUTATION
What role does mutation play in evolution?
Mutations are essential to evolution because they provide the phenotypic variation upon which natural selection acts. In this way, beneficial mutations become more prevalent within a population and the population will become more adapted to its environment over time.
What are some effects of mutations (are they good, bad, or neutral)?
Mutations may be beneficial (good), have no effect (neutral), or may be harmful (bad). The effect of a mutation depends on the phenotype it influences and the environment. An example of a beneficial mutation is a mutation that prevents HIV infection by causing a change in the membrane protein that the virus uses to enter immune system cells. An example of a neutral mutation is a change that codes for a synonymous amino acid. An example of a harmful mutation is the mutation that causes sickle-cell anemia by changing the protein structure of hemoglobin.
Are chromosomes only composed of DNA? If not, then what else is found in chromosomes?
No, chromosomes are composed of DNA wrapped around protein histones, forming nucleosomes and further wrapping around to form chromatin.
Is every gene in the genome of a cell expressed?
No, only some genes are expressed in each cell. For example, although skin and muscle cells from a single individual have the same genome, a skin cell will express different genes than the muscle cell. Different genes can also be expressed at different times in the cell lifecycle or in the lifetime of an individual.
______ - A point mutation that results in a "stop" codon.
Nonsense mutation
How is DNA repaired?
Nuclear DNA may be repaired during DNA replication by DNA polymerase and other proteins. Humans utilize excision repair, which includes both nucleotide excision repair (removal of errors and replacement of up to 30 nucleotides) and Base excision repair (replacement of one to five nucleotides and removal or errors mainly caused by oxidative damage). Humans may also utilize mismatch repair, which is detection and correction of loops caused by nucleotide mispairing. If repair protein genes are mutated, then mutations accumulate and can cause accelerated aging, cancer and disease.
How much of the human genome encodes for proteins? What is the purpose for the rest of the genome that doesn't code for proteins?
Only about 1.5% of human DNA codes for proteins. The remaining 98.5% includes viral DNA (remnants of DNA that originated from viral infections in our ancestors), noncoding RNAs (including pseudogenes, which can be transcribed, but cannot be translated into a protein), repetitive sequences (such as Alu repeat sequences), introns, promoters and other control sequences, small interfering RNAs (siRNA) and micro RNAs (miRNA).
____ change in a single DNA nucleotide; if a purine replaces a purine, or a pyrimidine replaces a pyrimidine, the point mutation is known as a transition. If a purine replaces a pyrimidine or vice versa, the point mutation is known as a transversion.
Point mutation -
_______=Specific sequence of amino acids in a polypeptide
Primary -
What are the four levels of protein structure?
Primary - Specific sequence of amino acids in a polypeptide Secondary - Interactions between nearby amino acids that cause shapes such as an alpha helix and a beta-pleated sheet within the polypeptide Tertiary - Interactions between distant amino acids in response to attraction or repulsion of water molecules (hydrophobic and hydrophilic interactions) Quaternary - Interactions between 2 or more separate polypeptides
= enzyme that adds a short RNA primer on each DNA template strand
Primase
What are prion diseases?
Prion diseases are caused by infectious misfolded proteins that induce other proteins to also become misfolded. Prion diseases are also known as Transmissible spongiform encephalopathies (TSEs). These diseases are fatal and incurable. Examples of prion diseases are Kuru, Mad cow disease (Bovine spongiform encephalopathy), Creutzfeldt-Jakob disease, and Gerstmann-Strussler disease.
How can a single polypeptide result in multiple proteins?
Proteins can be modified through the addition of sugars or lipids to make glycoproteins or glycolipids. Polypeptides can also be cut to make two or more proteins.
What are the building blocks of proteins? What are some functions of proteins?
Proteins consist of chains of amino acids joined together by peptide bonds. Proteins can function as structural components (hair, tendons, fingernails, ligaments), contractile components (muscles), immunity components (antibodies), transportation components (cell membrane proteins and hemoglobin), and enzymes, among many other functions (see Table 10.1).
_______ is the study of all of the proteins expressed in a cell, tissue, gland, organ, or the entire body.
Proteomics
What is Proteomics? How can proteomics be used to understand gene expression?
Proteomics is the study of all of the proteins expressed in a cell, tissue, gland, organ, or the entire body. It can be used to determine how gene expression differs between cells, how gene expression changes over time, and it can also be used to define functional groups of proteins. Additionally, it has great medical potential for determination of more specific treatments for certain individuals.
___________ is mass production of mutated genes, which can then be inserted into the genome.
Site-directed mutation
____ occur during DNA replication just prior to mitosis, which is the formation of somatic cells. Only descendent cells of this mutated somatic cell will be affected instead of all cells in the individual.
Somatic mutations
Does DNA polymerase ever put the wrong nucleotide in place? If so, which enzyme fixes the mistake?
Sometimes mistakes are made; however, they are usually corrected by DNA Polymerase as it proofreads while adding nucleotides.
- A point mutation that alters a site where introns are normally removed from the mRNA. This mutation may cause introns to be retained and translated, or exons to not be translated.
Splice site mutation
How can two people with a recessive phenotype (blue eyes) have a child with a dominant phenotype (brown eyes)?
Spontaneous mutations can arise due to an error in DNA replication. This can happen if replication occurs when the nitrogenous base of a nucleotide is in an alternate form known as a tautomer.
What is the difference between synonymous and nonsynonymous codons?
Synonymous codons are different codons that code for the same amino acid (redundant). Nonsynonymous codons code for different amino acids.
DNA contains the instructions for making proteins, much like a cookbook contains the instructions for making different types of food. Briefly describe this process (Central Dogma of Biology).
The Central Dogma of Biology states that genetic information is transcribed from DNA into RNA and that RNA is then used as a template to create a specific protein (transcription and translation).
What are the nucleotide and amino acid changes that result in sickle-cell anemia? How do they affect the β- globin protein? What is sickle-cell anemia?
The amino acid chain that codes for the β-globin protein in red blood cells is 146 amino acids long. In normal individuals, the 6th RNA codon reads GAG, which codes for Glutamic acid. In individuals with sickle-cell anemia, the RNA codon reads GUG, which codes for the amino acid Valine. This nonsynonymous amino acid change is caused by a mutation in the DNA, which replaces the normal T with an A. This change in amino acid sequence causes hemoglobin molecules to aggregate, forming rods which stretch red blood cells into long, sickle-like shapes that are prone to getting stuck in blood capillaries and cut off blood flow and supply to certain parts of the body, such as hands, feet and intestines. The disease sickle cell anemia is caused by having these sickle-shaped cells that do not function well in the circulatory system.
Why does the amino acid phenylalanine build up in the bodies of people with PKU?
The amino acid phenylalanine is broken down by an enzyme called phenylalabine hydroxylase. If this enzyme is misfolded and is no longer functional (correct protein structure is paramount to protein function STRUCTURE=FUNCTION), then phenylalanine will build up and will cause the disease PKU.
What are the chances of a gene mutation?
The chance of mutation is 1/100,000 on average.
What are the chances of a gene mutation? What is the spontaneous mutation rate of a gene if six individuals with the mutation are found in a sample group of 1000?
The chance of mutation is 1/100,000 on average. The spontaneous mutation rate in the sample group of 1000 is (6/(2 x 1000)) = 0.003 formula = # of cases/(2 x # of individuals examined)
What kind of bond holds the complementary strands of DNA together? Why is it important that DNA strands are held together by these bonds?
The complementary strands of the double helix are held together by relatively weak hydrogen bonds. These weak bonds allow the double helix to separate easily, making DNA replication an energetically efficient process.
How many blood proteins are found in blood plasma? Can the presence and frequency of these proteins change over time?
There are about 40,000 different proteins found in blood plasma and the protein found in greatest frequency is albumin. The protein profile of blood plasma can change depending on environmental conditions and is controlled by epigenetic changes to the genes coding for these proteins (turning them on or off). THIS ABILITY OF THE TISSUE TO ADAPT TO A CHANGING ENVIRONMENT IS POSSIBLE BC OF CHANGES IN GENE EXPRESSION--THAT IS HOW MUCH OF EACH PROTEIN IS MADE
What are transcription factors? What role do transcription factors play in transcription?
Transcription factors are proteins that initiate transcription of a specific gene on a chromosome. They help RNA polymerase bind to the promoter of the gene to be transcribed. (THIS IS DIFFERENT THAN PRIMASE.
DNA
Usually double-stranded Bases: Thymine (T), Adenine (A), Guanine (G) and Cytosine (C) Deoxyribose sugar Maintains protein-encoding information Cannot function as an enzyme Persists (is stable)
RNA
Usually single-stranded Bases: Uracil (U), Adenine (A), Guanine (G) and Cytosine (C) Ribose sugar Carries protein encoding information and controls how information is used Can function as an enzyme Transient (lasts for a short time)
Based on the sequence of DNA below, what is the mRNA sequence? a. Coding strand: 5'-AACGACATGCTGATACTGAGT-3' b. Template strand: 3'-CCGATGATCGTAGTGGGCAAA-5'
a. Coding strand: 5'-AACGACATGCTGATACTGAGT-3' 5'-AACGACAUGCUGAUACUGAGU-3' now the second strand has U instead of T RNA sequence is the same sequence as the DNA coding strand, with Uracil in place of Thymine b. Template strand: 3'-CCGATGATCGTAGTGGGCAAA-5' 5'-GGCUACUAGCAUCACCCGUUU-3'
If repair protein genes are mutated, then mutations ____
accumulate and can cause accelerated aging, cancer and disease.
____ increases the number of possible proteins that can be produced by the genome.
alternative splicing
Point mutation -
change in a single DNA nucleotide; if a purine replaces a purine, or a pyrimidine replaces a pyrimidine, the point mutation is known as a transition. If a purine replaces a pyrimidine or vice versa, the point mutation is known as a transversion.
PRIMASE
enzyme that adds a short RNA primer on each DNA template
The protein profile of blood plasma can change depending on environmental conditions and is controlled by _____
epigenetic changes to the genes coding for these proteins (turning them on or off).
The genes that code for these hemoglobin proteins are turned on and off during certain phases of the individual's development via ____________
epigenetic changes.
Chromatin is composed of DNA wound around proteins called_______.
histones
Transfer RNA (tRNA)
is a clover-leaf shaped structure which has an anticodon on one end (will bind to a matching codon of mRNA) and the corresponding amino acid on the other end. tRNA serves as the translator during the process of translation.
Messanger RNA (mRNA)
is the strand of RNA created from the transcription of the DNA template. This RNA contains information for making a specific protein. The mRNA strand is read in groups of 3 nucleotides, known as a codon. Each codon translates into a specific amino acid.
Splicing together the exons in differing orders and combinations allows for many different _______
isoform proteins.
Ribosomal RNA (rRNA)
joins with other proteins to form ribosomes. Ribosomes function to make proteins based on the information in a strand of mRNA.
____ groups prevent unwinding, and thus prevent transcription of certain genes.
methyl
___ which is detection and correction of loops caused by nucleotide mispairing.
mismatch repair
_____ are chemicals or radiation that increase the risk of mutation
mutagens
A______ is a change in the sequence of DNA that is present in less than 1% of the population.
mutation
including pseudogenes, which can be transcribed, but cannot be translated into a protein
noncoding RNAs
_____=(removal of errors and replacement of up to 30 nucleotides)
nucleotide excision repair
These amino acids are joined together by______ bonds to create _____.
peptide; polypeptides
A_______ is a mutation that is present in more than 1% of the population.
polymorphism
If proteins are misfolded, they may be corrected or they may be digested and recycled by a____.
proteasome
such as Alu repeat sequences
repetitive sequences
Base excision repair
replacement of one to five nucleotides and removal or errors mainly caused by oxidative damage).
This can happen if replication occurs when the nitrogenous base of a nucleotide is in an alternate form known as a_________.
tautomer
About 90% of all genes in the human genome are alternatively spliced. Additionally, introns in a ____ strand may code for proteins in a____ strand, also increasing the numbers of proteins that can be produced.
template coding
if a purine replaces a purine, or a pyrimidine replaces a pyrimidine, the point mutation is known as a
transition. c-t or t-c =pyrimidines; g-a or a-g =purines
MicroRNAs prevent ____
translation of mRNA into proteins
If a purine replaces a pyrimidine or vice versa, the point mutation is known as a.
transversion
remnants of DNA that originated from viral infections in our ancestors
viral DNA
Chromatin remodeling determines ____
which genes are transcribed
mismatch repair
which is detection and correction of loops caused by nucleotide mispairing.
The amino acid chain that codes for the ____ protein in red blood cells is ____ long. In normal individuals, the ____ RNA codon reads _____, which codes for____ acid. In individuals with sickle-cell anemia, the RNA codon reads _____, which codes for the amino acid_____. This _____ amino acid change is caused by a mutation in the DNA, which replaces the normal ___ with __. This change in amino acid sequence causes hemoglobin molecules to aggregate, forming rods which stretch red blood cells into long, sickle-like shapes that are prone to getting stuck in blood capillaries and cut off blood flow and supply to certain parts of the body, such as hands, feet and intestines. The disease sickle cell anemia is caused by having these sickle-shaped cells that do not function well in the circulatory system.
β-globin 146 amino acids 6th GAG Glutamic GUG Valine nonsynonymous T A