Engineering Questions with Answers - Multiple Choice Questions

MCQs on Gene Expression – Ribosomal RNA and tRNA

1 - Question

. In a mammalian cell, which is the most abundant type of RNA?
a) rRNA
b) mRNA
c) siRNA
d) tRNA

View Answer

Answer: a
Explanation: Ribosomal RNA (called rRNA) is the most abundant type of RNA in a cell. More than 80 percent of the RNA in a cell consists of ribosomal RNA. Other types of RNAs are transfer RNA and messenger RNA among others.




2 - Question

The human genome consists of _____ rDNA.
a) 2
b) 4
c) 5
d) 7

View Answer

Answer: a
Explanation: The human genome has five different clusters of ribosomal DNA, each on a different chromosome. Ribosomal DNA is the part of DNA that codes for ribosomal RNA, the most abundance type of RNA in a cell.




3 - Question

. Aggregated clusters of rDNA in a cell are called _______________
a) nucleoli
b) chromatin
c) chromosome
d) ribosome

View Answer

Answer: a
Explanation: In a non-dividing cell (the cell which is in interphase), the clusters of rDNA come together to form irregularly shaped nuclear structures called nucleolus (plural nucleoli). The nucleoli are dense with primary RNA transcripts.




4 - Question

Which of the following are ideal subjects for the study of rRNA synthesis and processing?
a) spermatocytes
b) mitochondria
c) oocytes
d) amphibians

View Answer

Answer: c
Explanation: Oocytes are the ideal candidates for the study of rRNA synthesis and processing. Amplification of rDNA is required by the fertilized egg to begin embryonic development; therefore oocytes contain hundreds of nucleoli that actively manufacture ribosomal RNA.




5 - Question

. Nontranscribed spacer is not transcribed.
a) True
b) False

View Answer

Answer: a
Explanation: Nontranscribed spacer is that region of the ribosomal gene cluster that is not transcribed into RNA. Transcription is the first step in genetic expression and regulation.




6 - Question

. How many types of distinct ribosomal RNAs are present in eukaryotic ribosomes?
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: d
Explanation: Eukaryotic ribosome or the 80S ribosome is made up of 2 unequal subunits(40S and 60S). The 40S subunit contains a 18S rRNA and the 60S subunit contains the 28S, 5S and the 5.8S rRNAs. Therefore the eukaryotic ribosomes have 4 rRNAs.




7 - Question

How many post-translational modifications occur in the pre-rRNA (primary transcript)?
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: b
Explanation: Two types of post-translational modifications are characteristic of pre-rRNA, large number of methylated nucleotides and pseudouridine residues. These make the pre-rRNA peculiar and contrasting from other primary RNA transcripts.




8 - Question

. Which of the following is a pre-rRNA?
a) 5S
b) 5.8S
c) 45S
d) 18S

View Answer

Answer: c
Explanation: The 45S RNA molecule is a pre-rRNA, of length 13,000 nucleotides. It is cleaved into 18S, 5.8S and 28S mature rRNA. Most of the pre- rRNA is spliced and reduced in length before turning into mature rRNA.




9 - Question

The processing of pre-rRNA is done using __________
a) nucleolus
b) mRNA
c) snoRNA
d) siRNA

View Answer

Answer: c
Explanation: The processing of pre- rRNA is done using the small nucleolar RNAs (called snoRNA) along with some proteins. Processing of pre- rRNA includes removal of non-coding sequences and posttranscriptional modifications.




10 - Question

. 5S rRNA is present only in eukaryotes.
a) True
b) False

View Answer

Answer: b
Explanation: 5s rRNA is present as part of the large ribosomal subunit in both eukaryotic and prokaryotic organisms. Unlike other types of rRNA, 5S rRNA is transcribed from a separate primary transcript.




11 - Question

. Which among the following have the largest number of tRNA genes?
a) humans
b) bacteria
c) yeast
d) fruit flies

View Answer

Answer: a
Explanation: Transfer RNAs (called tRNAs) play an important role in peptide synthesis. Humans contain about 1300 tRNA genes greater than other organisms mentioned. Bacteria has least number of tRNA genes.




12 - Question

. Transfer RNAs (tRNA) are transcribed by _________________
a) pre-RNA
b) rDNA
c) tDNA
d) siRNA

View Answer

Answer: c
Explanation: Clusters of tDNA located within the genome are responsible for the transcription of transfer RNAs. Transfer RNAs primarily function in the translation of proteins.




13 - Question

Ribonuclease P is involve in the processing of ___________________
a) sno RNA
b) rRNA
c) pre-tRNA
d) pre-mRNA

View Answer

Answer: c
Explanation: Ribobuclease P is an endonuclease present both in eukaryotes and prokaryotes. It is involved in the processing of pre-tRNA. Transfer RNA is synthesized from the processed primary transcript.

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