This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Genome Stability”.
1. Whole genome duplication is termed as __________________
Explanation: The process of polyploidization or whole genome duplication is evident in organisms such as Xenopus laevis, which have double the number of chromosomes as their clos cousins Xenopus tropicalis.
2. Which hypothesis was proposed by Susuma Ohno in 1971?
a) 2R hypothesis
b) 2T hypothesis
c) 2S hypothesis
d) 2P hypothesis
Explanation: In 1971, Susuma Ohno proposed the 2R hypothesis, in which he proposed that the vertebrates have evolved from invertebrates following two rounds of whole genome multiplication.
3. Amphioxus is a _____________________
a) cell organelle
b) marine animal
c) marine plant
Explanation: Amphioxus is a marine animal lacking a backbone but having certain other features that are common to vertebrates. It has been found out that homologous genes from vertebrates are double in number than that present in the amphioxi.
4. Gene duplication occurs by unequal crossing over.
Explanation: Gene duplication refers to duplication of a small part of single chromosome. Each gene in the genome has 1% chances of being duplicated in million years.
5. Unequal crossing over takes place due to _______________ of chromosomes.
Explanation: Unequal crossing over takes place due to misalignment of chromosomes during meiosis. As a result one chromosome receives and extra segment of DNA (duplication) and the other chromosome loses a segment of DNA (deletion).
6. Which of the following is an intervening, non-coding sequences?
Explanation: The part of gene which codes for amino acids in a polypeptide (gene product) is called exon. The intervening sequences which do not code for a gene product are called introns.
7. The globin gene is constructed from _____ exons and _______ introns.
a) 3, 2
b) 2, 3
c) 2, 2
d) 3, 3
Explanation: The globin gene is constructed from three exons and two introns. Fusion of two of the exons of globin genes millions of years ago led to the formation of globin-like polypeptides leghemoglobin and myosin.
8. Pseudogenes are _______________
c) existent in plants only
d) cannot be sequenced
Explanation: Pesudogenes are genes found in the clusters of genes that code for a specific polypeptide. Such genes are homologous to functional genes in the cluster but due to accumulated mutations, are rendered nonfunctional.
9. Who was the first person to suggest that genes were capable of moving around the genome?
a) James Watson
b) Barbara McClintock
c) Louis Pasteur
d) Gregor Mendel
Explanation: Barbara McClintock was the first person to suggest that genes were capable of moving around the genome. She was a geneticist working with maize at the Cold Spring Harbor Laboratories in New York.
10. Transposase is a __________ enzyme.
Explanation: Transposase is a bacterial enzyme, discovered in the late 1960s, that catalyzes the excision of a transposable element from the donor site to target site.
11. In human cell nucleus, at least _____ percent of DNA has been derived from transposable elements.
Explanation: In human cell nucleus, at least 45 percent of DNA is derived from transposable elements. More than 99% of transposable elements are incapable of moving either because they have been crippled by mutations or because their movement is suppressed by the cell.
12. Which of the following type of repeating sequence arise due to transposition of elements?
a) moderately repeating sequences
b) microsatellite DNA
c) minisatellite DNA
d) satellite DNA
Explanation: Moderately repeating sequences arise due to transposition of elements in the genome. These sequences are interspersed throughout the genome; examples include the L1 and Alu families.
13. DNA transposons found in the human genome are capable of movement.
Explanation: DNA transposons and retrotransposons are the two types of transposable elements found in the eukaryotes. Less than 5% occur as DNA transposons which are incapable of movement.
14. Alu sequences are ________________
a) dna transposons
c) viral elements
Explanation: Alu sequences are short interspersed nuclear elements (SINEs) about 300 base pairs in length, which are retrotransposons.
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