This set of Molecular Biology Multiple Choice Questions & Answers (MCQs) focuses on “Repeated Sequences are a Feature of Eukaryotic DNA”.
1. Which of the following is not a part of a gene?
a) Ori
b) Promoter
c) Operon
d) Terminator
View Answer
Explanation: Ori is the site for the origin of replication. This does not take part in any kind of gene expression and thus is not a part of any gene. Its function is to govern genome duplication.
2. What is the correct order for increasing gene density?
a) Bacteria, Virus, Fruit fly, Human
b) Fruit fly, Bacteria, Virus, Human
c) Human, Fruit fly, Bacteria, Virus
d) Virus, Bacteria, Fruit fly, Human
View Answer
Explanation: As the complexity of the organism increases the gene density decreases. Thus, gene density is inversely proportional to organism complexity. Therefore, viruses being the simplest organisms have the highest gene density and humans the lowest.
3. Which of these factors contribute to a decrease in gene density?
a) Operon
b) Intergenic sequence
c) Exon sequence
d) Cell size
View Answer
Explanation: As the genome size increases the DNA between two consecutive sequences increase, known as the Intergenic sequences. Thus, with the increase in genome complexity, regulatory sequences are required for the proper functioning of the different mechanisms. These regulatory sequences are stored in these Intergenic sequences.
4. What do you think is the requirement of Intergenic DNA in higher organisms?
a) Just genetic load
b) To avoid viable mutations
c) Helps in regulation of transcription
d) Helps in genome organization
View Answer
Explanation: With the increase in genome size the gene density decreases thus the rate of mutation at a viable point also decreases. This is why viable mutations in bacteria and viruses are more frequent than in humans.
5. Which of the following is not a character of unique Intergenic DNA?
a) Mutant genes
b) Pseudogenes
c) Palindromes
d) Nonfunctional gene fragments
View Answer
Explanation: Palindromes are specialized sequences identified by different enzymes and proteins. They are unique structures but are not found in unique Intergenic regions of DNA. These are generally found in the highly functioning DNA.
6. Which of the following is responsible for the formation of Pseudogenes?
a) Polymerase
b) Reverse transcriptase
c) Klenow fragment
d) Wrong primer
View Answer
Explanation: Pseudogenes arises from the action of enzyme reverse transcriptase. This enzyme copies RNA into double stranded DNA and are found in certain RNA viruses. Thus, when infected by these specific viruses the reverse transcriptase might copy the host cellular mRNA into a double stranded copy DNA. This copy DNA might get incorporated into the host genome giving rise to Pseudogenes.
7. With respect to microsatellite DNA which of the following is correct?
a) Tandem repeats
b) Dinucleotide repeats
c) 100 bp units
d) Inaccurate duplicating
View Answer
Explanation: Microsatellites are dinucleotide repeats such as “ATATATATATAT”. Thus, they are of a small stretch of DNA and are very short and less than 13 base pairs.
8. Genome – wide repeat unit are generally transposable elements.
a) True
b) False
View Answer
Explanation: Genome – wide repeat unit are greater than 100 bp in length. They are found in either as single copies dispersed throughout the genome or in clusters. They are of numerous classes but their most common feature is that all are forms of transposable elements.
9. Repeated DNA can be referred to as junk DNA.
a) True
b) False
View Answer
Explanation: Although it is tempting to refer to repeated DNA as junk DNA, they are stably maintained over the hundreds and thousands of years. This suggests that Intergenic DNA confers a positive value to the host organisms.
10. The simpler the organism the more likely they are to have transposable elements.
a) True
b) False
View Answer
Explanation: Even in the compact genomes of simpler organisms transposable elements are found. But the rate of success of occupying the genome is very less for these elements. This lack of success is likely a combination of inefficient duplication and/or more efficient elimination.
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