Chapter 8 - Mutations and Repair Flashcards
What is a mutation?
Permanent change in DNA sequence.
Mutations are defined as a permanent change.
What happens in forward mutations?
It alters wild-type alleles and is usually random and harmful.
What happens in reverse mutations?
It restores wild-type alleles and can counteract previous damages.
What can cause mutations?
Spontaneous degradation of nucleotides and DNA damage from chemicals, radiation, or free radicals.
Why might nucleotides spontaneously break apart?
Due to spontaneous depurination or hydrolysis.
How can the causes of mutations be categorized?
They can be placed on a large scale or small scale.
What are examples of small scale mutations?
Base substitutions, insertions, and deletions.
What are examples of large scale mutations?
Errors in Meiosis and Mitosis causing chromosomal deletions and duplications.
What are the types of mutations?
Point mutations –> Single nucleotide subs –> transition and transversion, insertion, and deletion.
What is a transition mutation?
Purine for purine or pyrimidine for pyrimidine substitution.
What is a transversion mutation?
Purine for pyrimidine or vice versa.
What are insertion and deletion in genetics?
Additions or losses of nucleotide pairs in a gene.
What is strand slippage?
A genetic process in which deletions and insertions of small contiguous repeats occur because of misalignment between DNA strands. This causes parts of template DNA to be copied more than once or to be missed during DNA replication.
What is DSB in the context of DNA?
Double-strand break, where both strands of the DNA molecule are broken.
What can cause double-strand breaks in DNA?
Chemical exposure, radiation, or spontaneous events.
What are hypotheses for the origin of bactericide resistance?
- Resistance is a physiological response to a bactericide. 2. Resistance arises from random mutation.
Explain the mutation rates.
Mutations are random and occur at a constant low rate.
Only mutations in ________ can be passed to offspring.
Sperm or egg cells.
Where are mutation rates high?
In eukaryotes and low in prokaryotes.
What raises the risk of mutations?
Cell divisions, metabolic activity, radiation, age, and exposure to chemicals.
What are the causes of spontaneous mutations?
Depurination, deamination, base tautomerization, and polymerase copying error.
What is depurination?
Purines fall off the nucleotide and occurs 1000 times a day.
What is deamination?
When an amine group is removed from a base.
What is tautomerization?
Structural isomers that spontaneously change and make base pairs connect incorrectly.
What can DNA damage-induced mutations lead to?
Transversions and oxidation of guanine.
What type of radiation is known to cause DNA damage?
Ionizing radiation.
What type of DNA damage can ionizing radiation cause?
Double-Strand Breaks (DSB).
What are some potential consequences of DNA damage from ionizing radiation?
Deletion, cell death, chromosomal rearrangements.
What is a characteristic of repair pathways for DNA damage caused by ionizing radiation?
They were error-prone.
What does UV irradiation cause?
DNA damage in the form of thymine dimers.