Unit 14: Mutation and DNA Repair Flashcards
What is a mutation?
A change in the DNA sequence that gives a different protein or no protein.
What are germ-line mutations?
Mutations that occur in germ-line cells, giving rise to sperm and egg, are called germ-line mutations.
Can germ-line cells be passed generation to the next?
Yes, germ-line mutations can be passed from one generation to the next.
What are somatic mutations?
Cells not in the germ line are somatic cells, thus, mutations in such cells are called somatic mutations.
Can somatic cells be passed generation to the next?
No, somatic cells divide by mitosis and only direct descendants of the original mutated cell will carry the mutation.
What is the fitness of a mutation?
The fitness of a mutation describes its value to the survival and reproductive success of the organism.
What are lethal mutations?
Many mutations are lethal and cause embryos to be non-viable.
What are harmful mutations?
Non-lethal, but lower survival and reproduction.
What are silent mutations?
Neutral, no effect on phenotype.
What are beneficial mutations?
Useful, usually in a new environment.
What are the four types of mutations?
- Bases changed (substitution).
- Bases removed (deletion).
- Bases added (insertion)
- Bases inverted (inversion)
What are the four effects of mutations?
- Silent mutation
- Missense mutation
- Nonsense mutation
- Frameshift mutation
What is a silent mutaiton?
A base-pair change that does not alter the resulting amino acid due to the redundancy of the genetic code.
What is a missense mutation?
A base-pair change that results in an amino acid change in the protein.
What is a nonsense mutation?
A base-pair change that creates a stop codon in place of a codon specifying an amino acid.
What is a frameshift mutation?
An insertion or deletion that causes the reading frame to shift.
__ _____ ______ is the result of a single base substitution.
Sickle Cell Anemia is the result of a single base substitution.
________ _______ may cause the _____ disorder
Different mutations may cause the same disorder.
What causes a mutation?
Can occur spontaneously or can be induced by a mutagen.
What is a mutagen?
A mutagen is an agent that causes a mutation.
What are spontaneous mutations?
Bases that are found in uncommon forms that base pair with a non-complementary base.
If a spontaneous mutation occurs during replication…
a mutation will persist in one copy of the DNA.
What is DNA symmetry and how may it lead to spontaneous mutations?
DNA symmetry means the sequence is very repetitive or mirror-like.
(Ex. AAAAAA, GCGCGC, TACTACTAC).
This makes it hard for enzymes (like DNA polymerase) to read or copy it accurately during replication.
Mistakes = spontaneous mutations
How do duplicated copies of genes cause misalignment of genes during crossing over?
If a gene is duplicated, it can confuse chromosomes during crossing over. This misalignment may cause unequal swaps, leading to duplications or deletions — a type of spontaneous mutation.
What condition is caused as a result of misalignment during crossing over?
Red-Green Colorblindness
What are trinucleotide repeat expansion disorders?
Trinucleotide repeat expansion disorders (TACTACTAC) involve strand slippage mutations that cause some hereditary diseases in humans and other organisms.
What are induced mutations?
Induced mutations are DNA changes caused by something in the environment, like chemicals, radiation, or viruses.
What are nucleotide base analogs as chemical mutagens that are induced mutations?
Can mimic bases or cause chemical changes in bases causing a mismatch base pairing.
What is an example of a nucleotide base analog?
5-bromouracil acts as thymine. Mispairs with guanine (G) rather than pairing with adenine (A) during replication.
What are intercalating agents as chemical mutagens that are induced mutations?
Are agents that can get in between bases (intercalate) during replication.
What is an example of an intercalating agent?
Proflavin slips into the DNA molecule between two adjacent base pairs and causes a frameshift mutation.
What are photoproducts as radiation mutagens that are induced mutations?
Photoproducts are abnormal structures in DNA that form when UV light damages the DNA bases.
How do photoproducts cause mutations?
- Can physically break DNA.
- Can cause chemical reactions that kink the DNA and cause error prone replication and transcription.
What are infectious agent mutagens that are induced mutations? (3 things)
Bacteria and viruses can:
1. Physically break DNA strands.
2. Change DNA methylation.
3. Impair DNA repair mechanisms.
What stops some DNA damage?
All organisms possess
highly conserved DNA repair systems to detect and repair DNA damage.
What happens if organisms can’t repair DNA damage?
Unrepaired DNA damage can have harmful consequences such as cancer.
What does accumulated DNA damage lead to?
Accumulating DNA damage leads to cancer and aging.
What two things do DNA repair mechanism do to damaged DNA?
- Directly repair DNA damage.
- Allow the organism to avoid the problems caused by unrepaired damage (cell cycle delay/arrest in G0 or cell death)
What does it mean when cells turn senescent?
Cells turn senescent (fully metabolic but stuck in G₀ of the cell cycle) or undergo cell death to avoid passing on damaged DNA → Leads to aging.
