Unit 3 (Week 11 Mutations DNA Repair and Cancer) Flashcards
The children at this camp have inherited a disorder called xeroderma pigmentosum (XP), which makes them highly sensitive to sunlight. Their skin will blister or freckle on minimum exposure to sunlight. Of greater concern, however, is skin cancer.
What explains the symptoms of XP?
Individuals with this condition are highly susceptible to mutation, which is defined as a heritable change in the genetic material.
Should we be afraid of mutations?
Yes and no. On the positive side, mutations are essential to the long-term continuity of life. Mutations provide the foundation for evolutionary change. They supply the variation that enables species to evolve and become better adapted to their environments. On the negative side, however, new mutations are more likely to be harmful than beneficial to the individual. The genes within modern species are the products of billions of years of evolution and have evolved to work properly. Random mutations are more likely to disrupt genes rather than enhance their function.
A mutation is best defined as ______.
Multiple choice question.
a heritable change in the genetic material
an exchange of genetic material between two individuals
a permanent change in protein structure
a heritable change in the genetic material
Mutations are essential for the long-term continuity of life because they supply the _______________-
variation that is the foundation for evolutionary change.
genetic, gene, genomic, DNA, heritable, enabling, allelic, allele, or essential
Relatively small changes in DNA sequence are known as:
Multiple choice question.
nucleotides
splice junctions
transposable elements
gene mutations
mutagens
gene mutations
What are gene mutations?
Relatively small changes in the sequence of bases in a particular gene.
What are the two basic types of changes to a gene? (2)
- Base sequence within a gene can be changed
2. One or more base pairs can be added to or removed from a gene.
What is a mutation that affects only a single base pair within DNA or that involves the addition or deletion of a single base pair to a DNA sequence?
Point mutation
What is a mutation that involves the substitution of a single base in the DNA for another base?
Base substitution
Where must a mutation occur that can alter the sequence in a variety of ways?
The coding region of a protein-encoding gene.
What is a gene mutation that does not alter the amino acid sequence of the polypeptide, even though the base sequence has changed?
Silent mutation
Remember: Genetic code is degenerate meaning that one codon can specify the same amino acid. These mutations happen normally in the third base.
What is a base substitution that changes a single amino acid in a polypeptide?
Missense mutation.
Why might a missense mutation not alter protein function?
It changes only a single amino acid within a polypeptide that is typically hundreds of amino acids in length. A missense mutation that substitutes an amino acid with a chemistry similar to the original amino acid is less likely to alter protein function.
Example: Missense mutation that substitutes a glutamic acid for an aspartic acid may not alter protein function because both amino acids are negatively charged and have similar side chain structures.
What disease is an example of a striking change when a missense mutation occurs?
Sickle cell disease.
This is a disease due to a mutation in a hemoglobin gene that results in sickle-shaped red blood cells that are less able to move smoothly through capillaries and can block blood flow, resulting in pain and cell death of the surrounding tissue.
What gene specifically is affected in sickle cell disease?
Missense mutation of the B-globin gene.
The 6th amino acid is changed from a glutamic acid to valine. The striking difference between these two amino acids is one is hydrophilic while the other is hydrophobic, changing the structure of the cell.
Based on the fiber-like structures seen in part (c) of this figure, what aspect of hemoglobin structure does a glutamic acid at the sixth position in normal β-globin prevent? Speculate as to how the charge of this amino acid may play a role.
At neutral pH, glutamic acid is negatively charged. Perhaps the negative charges repel each other and prevent hemoglobin proteins from aggregating into fiber-like structures.
What is a mutation that changes a normal codon into a stop codon; this causes translation to be terminated earlier than expected, producing a truncated polypeptide?
Nonsense mutation
What is a mutation that involves the addition or deletion of a number of nucleotides that is not a multiple of three and alters the reading frame of a protein-encoding gene?
Frameshift mutation
T/F A mutation can occur within a noncoding DNA sequence and affect gene expression.
True
Ex. The promoter region with a mutation may increase or decrease the rate of transcription.
What can happen if there is a mutation in the regulatory elements or operator site in the context of the lac operon?
Regulatory elements such as the lac operator site in E. coli, which is recognized by the lac repressor, can disrupt the proper regulation of the lac operon. The lac repressor would not bind to the lac operator site causing the operon to constitutively be expressed and waste energy and resources within the cell.
What are the two types of cells that geneticists classify cells as?
Germ-line cells & somatic cells.
What are the cells that give rise to gametes, such as an egg and sperm cells?
Germ line
A germ-line mutation can occur directly in an egg or sperm cell, or it can occur in a precursor cell that produces the gamete.
What constitutes for all cells within the body of an animal or plant except those that give rise to gametes?
Somatic cells.
Example is skin and muscle cells. The larger the affected area, the earlier the mutation happened after the embryo was created.
What do you call an individual with somatic regions that are genetically different from each other?
Mosaic.
Ex. A child with a grey streak of hair. This is due to a somatic mutation in a single cell during embryonic development. This cell continued to divide to produce a streak of white hair. This also creates a mosaic.
Can this child with a streak of white hair transmit this trait to his future offspring?
This trait is due to a mutation that occurred in a somatic cell, so it cannot be transmitted to the individual’s offspring.
How do point mutations affect DNA sequences? Choose all that apply.
Multiple select question.
by adding or subtracting a single base pair
by rearrangement of nucleotides
by inserting a sequence of multiple base pairs into the existing DNA molecule
by substituting one base for another
by reinserting a portion of the sequence in reverse order
by adding or subtracting a single base pair
by substituting one base for another
What is a point mutation?
Multiple choice question.
A mutation that occurs in a somatic cell
A mutation that occurs at a particular developmental stage
A mutation that changes a normal codon to a stop codon
A mutation that affects only a single base pair
A mutation that is induced by an environmental agent
A mutation that affects only a single base pair
A heritable change in genetic material is known as a(n) _________.
Mutation
Consider the following wild-type DNA sequence: 5’-CCAAGGTT-3’. Which of the following mutations is a base substitution?
Multiple choice question.
5’-CCCAAGGTT-3’
5’-CCAGGTT-3’
5’-CCCAGGTT-3’
5’-CCCAGGTT-3’
True or false: New mutations are much more likely to be harmful than beneficial to the individual.
True false question.
True
False
True
