Origins of Mutations and DNA Replication/Repair Flashcards
1
Q
Depurination
A
- -loss of 5,000 bases everyday
- -adenine or guanine
- -hydroylzation of bond between base and deoxyribose
2
Q
Deamination
A
- -most common one is spontaneous conversion of cytosine to uracil
- -messes things up b/c cytosine pairs w/ guanine but uracil would pair w/ adenine
3
Q
Pyrimidine Dimers
A
–caused by UV light
dimerization of adjacent thymine bases on same DNA strand
4
Q
4 Levels of Mutations
A
- -gene: single bases switches
- -chromosomal: rearrangements, deletions or duplications of chromosomal regions
- -genomic: surplus or loss of chromosomes
- -mutations impacting chromatin: changes in methylation of DNA or in modification of histone proteins
5
Q
Frequency in Types of Mutations
A
from most common to least: genomic>chromosomal>gene
6
Q
Missense vs. Nonsense mutations
A
- -missense: changes AA codon
- -nonsense: introduces stop codon
7
Q
Small insertions or deletions:
3 mechanisms?
A
- -incorrect recombination
- -strand slippage
- -intercalating agents
8
Q
Frameshift mutations
A
- -insertion/deletion not in multiple of 3 in gene
- -25% of human genetic diseases
9
Q
Importance of Homologous Crossover
A
–recombination of genetic material–constantly creating new combinations
10
Q
Chiasmata
A
–holds chromosomes together after crossing over occurs
11
Q
Anaphase
A
- -also called disjunction
- -separation of chromosomes
- -nondisjunction can occur and leads to genetic disease and increases w/ maternal age
12
Q
Problems which can occur during crossover
A
- -misaligned crossover: insertion or deletion of sections of chromosomes
- -nondisjunction
13
Q
Nondisjunctions compatible w/ life
A
- -monosomy = always fatal
- -Trisomy 13 (Patau syndrome), 18 (edward syndrome), 21 (Down) are all viable
- -sex chromosome anomalies: 47XXX, 48XXXX, 49XXXXX, 48XXXY, 49XXXXY
- -triploidy or tetraploidy always fatal
14
Q
Mosaicism
A
- -cells in single person that have different genotype
- -occurs when early on cells develop somatic mutation (during embyrogenesis)
- -2-4% of Pt. with trisomy 21 are mosaics (some cells lose 3rd chromo. 21 and develop as normal cells)
15
Q
Strand Directed Mismatch Repair
A
- -system must determine which strand is original parental strand; does this by identifying “nicks” in daughter strand
- -repair enzyme recognizes distortions in DNA helix and chews out wrong NT and DNA pol replaces it