This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “DNA Repair”.
1. Mutations in the DNA may be passed to the next generation.
Explanation: Mutations in the DNA of a germ cell (gamete) can pass to the next generation and may even give rise to genetic disorders that are inherited. This forms the basis of diseases and abnormalities that run in the family.
2. How many pathways of nucleotide excision repair exist?
Explanation: Nucleotide excision repair (NER) operates by excising the lesions and then repairing it. There are two pathways of this repair system – transcription coupled pathway and global genomic pathway.
3. Which repair system operates to remove the altered bases generated by reactive chemicals present in the diet?
a) Base excision repair
b) Nucleotide excision repair
c) Mismatch repair
d) Double-stranded breakage repair
Explanation: Base excision repair system (BER) operates to remove or rectify the altered nucleotides generated as a result of action of reactive chemicals presented in the diet or generated by the metabolism.
4. Which repair system operates to repair DNA strands that are actively transcribed?
a) Double-strand breakage repair
b) Nucleotide excision repair
c) RNA repair
d) Messenger RNA repair
Explanation: The template strands of genes that are actively being transcribed are repaired by the transcription coupled pathway of the nucleotide excision repair (NER) system.
5. A mismatched base pair can cause ________________ in the double helix.
a) change in geometry
b) change in location
c) change in size
d) change in alkalinity
Explanation: A mismatched base pair can cause a distortion in the geometry of the double helix, which is recognizable by a repair enzyme. This process of repairing is called mismatch repair.
6. Which of the following does not introduce double-strand breaks in the DNA?
a) Gamma rays
b) Cancer drugs
c) Free radicals
d) Inherited mutations
Explanation: Many internal and external agents cause double-stranded breaks in the DNA double helix. Ionizing radiations, certain chemicals and free radicals are examples of the causative agents of these breaks.
7. The NHEJ pathway is used to rectify __________________ in the DNA.
a) nucleotide substitutions
b) double-strand breaks
c) single-strand breaks
d) mismatched basepairs
Explanation: The nonhomologous end joining pathway (NHEJ) is a pathway to repair double-strand breaks in the DNA. These are introduced by agents such as ionization radiations, cancer drugs etc.
8. Xeroderma pigmentosum is caused by ______________________
a) UV radiations
c) Gamma radiations
Explanation: Xeroderma pigmentosum (XP) is a rare genetic disorder due to deficiency in nucleotide excision repair system that cannot remove segments of DNA damaged by ultraviolet radiations.
9. How many types of skin cancers can develop by overexposure to ultraviolet rays?
Explanation: Three types of cancer – basal cell carcinoma, squamous cell carcinoma and malignant melanoma. The first two types are the most common and can be excised in a clinic, while the third type is a potential killer.
Sanfoundry Global Education & Learning Series – Cell Biology.
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