What is a mutation?
A mutation is a permanent change in the DNA sequence that can affect the structure or function of a protein.
What are the two main categories of mutations?
Gene mutations: Changes within a single gene.
Chromosomal mutations: Changes in chromosome structure or number.
What are point mutations?
Mutations that affect a single nucleotide pair in DNA.
What are the three types of point mutations?
- Silent mutation: No change in amino acid.
- Missense mutation: Changes one amino acid.
- Nonsense mutation: Creates a stop codon, ending translation early.
What is a silent mutation?
A change in DNA that does not alter the amino acid sequence of the protein due to redundancy in the genetic code.
What is a missense mutation?
A point mutation that substitutes one amino acid for another in the protein.
What is a nonsense mutation?
A mutation that changes an amino acid codon into a stop codon, prematurely ending protein synthesis.
What are frameshift mutations?
Mutations caused by insertions or deletions that change the reading frame of the genetic code.
What is an insertion mutation?
The addition of one or more nucleotides into a DNA sequence.
What are chromosomal mutations?
Large-scale mutations that change the structure or number of chromosomes.
What is a deletation mutation?
The loss of one or more nucleotides from a DNA sequence.
What are the four main types of chromosomal mutations?
- Deletion: Loss of a chromosome segment.
- Duplication: Repeat of a segment.
- Inversion: Segment reversed within the chromosome.
- Translocation: Segment moves to a different chromosome.
What is non-disjunction?
Failure of chromosomes to separate properly during meiosis, leading to gametes with abnormal chromosome numbers.
What is a spontaneous mutation?
A random mutation occurring naturally during DNA replication or repair.
What is an induced mutation?
A mutation caused by external factors (mutagens) like radiation or chemicals.
What are mutagens?
Physical or chemical agents that cause changes in DNA sequence (e.g., UV light, X-rays, cigarette smoke).
How does UV light cause DNA mutations?
UV light creates thymine dimers, where adjacent thymines bond together, distorting the DNA helix.
What is Depurination?
A spontaneous loss of a purine base (A or G) from DNA, leading to replication errors.
What is deamination?
The removal of an amino group from a base, such as cytosine converting to uracil.
What repair mechanism fixes mismatched bases in DNA?
The mismatch repair system, which removes and replaces incorrect nucleotides.
What is base excision repair?
A DNA repair process that removes and replaces damaged bases caused by oxidation, alkylation, or deamination.
What is nucleotide excision repair?
A repair mechanism that removes bulky lesions such as thymine dimers and fills the gap using DNA polymerase and ligase.
What is the ames test?
A test that determines whether a chemical is mutagenic by measuring its ability to induce mutations in bacteria.
What are somatic mutations?
Mutations that occur in body cells and are not passed to offspring.
