02.12 - DNA Mutagenesis, Repair, and Relevant Diseases Flashcards
It refers to any permanent heritable change in the DNA base sequence of an organism.
Mutation
Which of the following process makes use of DNA recombination?
a. DNA repair
b. Immunoglobulin rearrangement
c. Crossing-over during meiosis
d. Integration of viral DNA
All of the above makes use of DNA recombination.
A replacement of a single base with another single base nucleotide is called ______________.
Point mutation
A certain mutagen caused the mutation in the short DNA sequence 5’-GGACTCG-3’. The new sequence reads 5’-GGGCTCG-3’. What type of point mutation occurred?
Transition
A mutation from 5’-ACCGTTA-3’ to 5’-ACCTTTA-3’ is what type of point mutation?
Transversion
When a point mutation results in the same amino acid, it is called a ____________.
Silent mutation
When a point mutation results in a new codon that codes for a different amino acid, a _____________ has occurred.
Missense mutation
A missense mutation that resulted in the replacement of aspartic acid with glumatic acid, which are both hydrophilic in nature, is said to be _____________.
Conservative
When a missense mutation results in a different amino acid with different properties, it is said to be ____________.
Non-conservative
When a point mutation results in a premature stop codon, a ___________ has occurred.
Nonsense mutation
____________________ results after the deletion or addition of a number of bases not divisible by three.
Frameshift mutation
_______________ occurs when large areas of chromosomes are lost during unequal crossover in meiosis.
Large segment deletion
DNA repair occurs during what phase of the cell cycle?
a. G1
b. G2
c. S
d. M
b. G2 (after DNA replication has occurred after the S phase)
Arrange the steps of DNA repair in order.
I - Endonuclease nicks the mismatched strand and mismatched base is removed
II - DNA polymerase I and DNA ligase completes repair
III - Mismatched strands are identified
a. I-II-III
b. I-III-II
c. III-II-I
d. III-I-II
d. III-I-II
Also known as the Lynch syndrome, this early onset hereditary disease is characterised by the familial clustering of cancers at several sites.
Hereditary non-polyposis colorectal cancer (HNPCC)
Which of the following is the cause of HNPCC?
a. Microsatellite instability
b. Mismatch repair deficiency
c. Thymine dimerization
d. A and B
d. A and B
Name two genetic pathways that can lead to cancer.
Activation of oncogenic pathways
Inactivation of tumor suppressor genes
What is the cause of xeroderma pigmentosum?
a. Failure to repair mismatched DNA strand
b. Inactivation of timor suppressor genes in skin cells
c. Large segment deletion
d. Failure to replicate DNA due to thymine dimerization
d. Failure to replicate DNA due to thymine dimerization
Arrange the steps of abnormal base replacement in order:
I - Formation of apyrimidinic or apurinic site (AP site)
II - DNA polymerase and DNA ligase complete the repair
III - Deoxyribose-phosphate lyase removes the single empty sugar-phosphate residue
IV - Abnormal nitrogenous base is removed by cleaving N-glycosidic bond
V - AP-endonucleases make a nick at the 5’ site of the AP site
a. IV-I-V-III-II
b. IV-V-I-III-II
c. V-IV-I-II-III
d. V-I-III-IV-II
a. IV-I-V-III-II
In DNA repair of abnormal bases, what enzyme hydrolytically cleaves the abnormal nitrogenous base from the deoxyribose-phosphate backbone?
Glycosylases (Tip: Remember that it cleaves the N-glycosidic bond between the nitrogenous base and sugar)
