Chapter 14: DNA Repair Flashcards
What is the definition of a Mutation? What are 3 ways they can occur?
Any heritable change in the genetic material.
- Spontaneous Mutations (most common)
- proofreading failure
- Mutagens
(DNA can be damaged by many different things)
What are some agents that will damage DNA?
- X-rays
- UV light
- Chemicals
What are the natural ways in which your cells maintain DNA without mutations?
Proofreading and Mismatch Repair
What organisms are mutation rates the highest? Why?
RNA Viruses and Retroviruses are highest because RNA is prone to breakage and lack a proofreading function
(ex: HIV)
What are the 2 mutation categories? Give an example of a Small-Scale Mutation and a Large-Scale Mutation.
- Small-Scale:
- Nucleotide substitution or point mutation
- Synonymous (silent) mutations
- Nonsynonymous (missense) mutations
- Nonsense mutations
- Large-Scale (chromosomal mutations):
- Frameshift
- Insertion
- Deletion
What are Point Mutations? Are they common?
THE MOST COMMON
Small-Scale Mutations that only affects one or very few nucleotides in a gene sequence:
- generally Synonymous (Silent: no change in amino acid)
- can be Nonsynonymous (Missense: change in coded amino acid)
- can also cause Nonsense mutations
When codon changes to a stop codon
What type of mutation causes sickle cell anemia?
POINT MUTATION:
when the adenine base in GAG is replaced by a thymine base, changing the triplet to GTG
What are Frameshift Mutations?
Large-Scale Mutations caused by a deletion or insertion in a DNA sequence (1 or 2 bases) that shifts the way the sequence is read:
- leads to incorrect codons which code for incorrect amino acids
What type of mutation causes cystic fibrosis?
FRAMESHIFT MUTATION:
deletion of 3 nucleotides resulting in abnormal secretions in the lungs, liver, pancreas ,and other glands
Describe the following mutations:
Silent
Nonsense
Missense (conservative and nonconservative)
Silent Mutation: a type of point mutation that does not result in a change in the amino acid sequence of a protein
Nonsense Mutation: a type of point mutation that introduces a premature stop codon in the DNA sequence, leading to the premature termination of protein synthesis
Missense Mutation: a type of point mutation that causes a change in the amino acid sequence of the encoded protein
- Conservative: the substituted amino acid has similar chemical properties to the original one
- Nonconservative: the substituted amino acid has different chemical properties from the original one
What are Transposons? How do they play a role in DNA mutation?
DNA sequences that can move from position to another in the genome
- Duplication: sequence is doubled
- Deletion: sequence is gone
- Transposable elements can affect the normal function of a gene, even damaging introns and exons
What is the difference between Somatic Mutations and Germ-Line Mutations?
Somatic Mutations:
happen AFTER conception and are only present in affected progeny cells through mitotic cell divisions. NOT PASSED ON TO CHILDREN!
Germ-Line Mutations:
are changes in DNA that are inherited from egg and sperm cells DURING conception and are present in all the cells of our body because of meiosis. CAN BE PASSED TO CHILDREN
What determines the rate (frequency) of a mutation? Do males or females generally have a greater rate of mutation?
RATE/FREQUENCY OF MUTATION DEPENDS ON CELL TYPE
- Males have greater rate of mutation
What is a Neutral Mutation?
A mutation that has little or no effect on the individual’s ability to survive and reproduce, and it does not significantly impact the organism’s phenotype or fitness
What are some of the the benefits of mutations?
- Increase the likelihood of an organism surviving and being naturally chosen
- Allow humans to adapt to their environment
- Broaden the population’s diversity
