This set of Molecular Biology Multiple Choice Questions & Answers (MCQs) focuses on “Coding and Non-Coding RNA”.
1. Non – coding sequence in mRNA is known as __________
a) Template
b) Non – template
c) Intron
d) Exon
View Answer
Explanation: Long stretches of non – coding DNA are found within most eukaryotic genes. These sequences are known as introns which are removed from the pre-mature RNA to produce mature RNAs.
2. Which of the following organisms have monocistronic DNA?
a) Virus
b) Bacteria
c) Fungi
d) Yeast
View Answer
Explanation: The bacterial genome is monocistronic. This means that the genes are not disrupted by the presence of introns.
3. Which of the following organisms have overlapping genes?
a) Virus
b) Bacteria
c) Fungi
d) Yeast
View Answer
Explanation: The viruses have overlapping genes to accommodate the genome in such a small cell. The bacterial cell is monocistronic whereas all eukaryotic cells are polycistronic.
4. Introns were first discovered in __________
a) 1958
b) 1955
c) 1966
d) 1977
View Answer
Explanation: Introns were first discovered in 1977 during the studies of replication of adenovirus in cultured human cells. It was discovered independently in the laboratories of Phillip Sharp and Richard Roberts.
5. Adenovirus is a useful model of studying gene expression because __________
a) High infection rate
b) Assured transformation
c) High protein production
d) Short duplication time
View Answer
Explanation: Adenovirus is a useful model of studying gene expression because of two reasons:
i) The size of the viral genome is small that is only 3.5*104 base pairs long.
ii) The adenovirus mRNAs are produced at high levels in infected cells thus yielding a high amount of protein.
6. Mouse β – globin gene has __________ introns.
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: Mouse β – globin gene has 2 introns. This gene encodes the β – subunit of haemoglobin. This is found by the observations produced by the electron microscopic analysis of RNA – DNA hybrids and subsequent nucleotide sequencing of cloned genomic DNA and cDNAs.
7. The amount of exon in the eukaryotic genome is higher than that of the introns.
a) True
b) False
View Answer
Explanation: The intron – exon structure of many eukaryotic genes is quite complicated, and the amount of DNA in the intron sequences is often greater than that in the exons. For example, an average human gene contains about 10 exons, interrupted by introns distributed over approximately 56 kb of genomic DNA. The exons generally total only about 4.1 kb including both the 5’ and 3’ ends of the mRNA that are not translated into proteins.
8. The mRNA of which eukaryotic protein lacks introns?
a) Haemoglobin
b) Myoglobin
c) Histone
d) Polymerase
View Answer
Explanation: Introns are present in almost all genes of complex eukaryotes, although they are not universal. Almost all histone genes for example, lacks introns, so introns are not clearly not required for gene function in eukaryotes.
9. Introns are nothing more than genetic load in the eukaryotic genome.
a) True
b) False
View Answer
Explanation: Although most introns do not specify the synthesis of protein product, they have other cellular activities. Many introns encode functional RNAs, including the small nucleolar RNAs that function in ribosomal RNA processing and the microRNAs, which are major regulators of gene expression in eukaryotic cells. Introns also contain regulatory sequences that control transcription and mRNA processing.
10. Presence of introns facilitates the formation of several different mRNAs, thus increasing protein yield of different types but from same gene.
a) True
b) False
View Answer
Explanation: The presence of introns facilitates the formation of several different mRNAs by the process of alternative splicing. In this, the exons of the gene join in different combinations resulting in the synthesis of different proteins from the same gene.
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