This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Gene Expression – Ribosomal RNA and tRNA”.
1. In a mammalian cell, which is the most abundant type of RNA?
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. The human genome consists of _____ rDNA.
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. Aggregated clusters of rDNA in a cell are called _______________
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. Which of the following are ideal subjects for the study of rRNA synthesis and processing?
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. Nontranscribed spacer is not transcribed.
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. How many types of distinct ribosomal RNAs are present in eukaryotic ribosomes?
Explanation: The eukaryotic ribosomes contain 4 distinct ribosomal RNAs. Three RNAs (28S, 5.8S, 5S) in the large ribosomal subunit and, one RNA (18S) in the small subunit. This composition varies for prokaryotic genomes.
7. How many post-translational modifications occur in the pre-rRNA (primary transcript)?
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. Which of the following is a pre-rRNA?
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. The processing of pre-rRNA is done using __________
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. 5S rRNA is present only in eukaryotes.
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. Which among the following have the largest number of tRNA genes?
d) fruit flies
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. Transfer RNAs (tRNA) are transcribed by _________________
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. Ribonuclease P is involve in the processing of ___________________
a) sno RNA
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.
Sanfoundry Global Education & Learning Series – Cell Biology.
To practice all areas of Cell Biology, here is complete set of 1000+ Multiple Choice Questions and Answers.