This set of Class 12 Biology Chapter 6 Multiple Choice Questions & Answers (MCQs) focuses on “Transcription Unit and the Gene”.
1. It is difficult to define a gene in terms of its DNA sequence.
a) True
b) False
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Explanation: Genes are the functional units of a living organism. They are the information carriers that are present on the DNA. But a gene cannot be entirely defined based on its DNA sequence alone. The DNA sequence coding for either the tRNA or the rRNA also defines the gene.
2. What is a cistron?
a) A gene coding for RNA
b) A segment of DNA responsible for producing the nuclear coat
c) A segment of DNA coding for polypeptides
d) A gene coding for the template strand of DNA
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Explanation: A cistron is the segment of a DNA. It is responsible for coding polypeptide chains. This is seen during the process of protein synthesis.
3. Which of the following is monocistronic?
a) Fungi
b) Eukaryotes
c) Bacteria
d) Virus
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Explanation: Cistrons are the segments of the DNA helical structure which code for polypeptide chains. The structural gene in the transcription unit can be either monocistronic or polycistronic. The monocistronic genes are mostly present in eukaryotes.
4. Which of the following is polycistronic?
a) Bacteria
b) Rats
c) Snakes
d) Hamster
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Explanation: The polycistronic organisms can code for more than one polypeptide sequence as individuals inside the RNA molecule. Examples of such are the bacteria and prokaryotes.
5. The genes in eukaryotic organisms are split.
a) True
b) False
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Explanation: The presence of monocistronic structural genes results in the formation of interrupted coding sequences. The monocistronic structural genes are present in the eukaryotes. So, their genes are split.
6. Which of the following is the key difference between exons and introns?
| S. No | Exons | Introns |
| I | They are non-coding sequences | They are the coding sequences |
| II | They are interrupted by Introns | They appear in mature RNA |
| III | They appear in mature RNA | They interrupt the sequences of the exons |
| IV | They are the unexpressed sequences | They appear in non-coding sequences |
a) I
b) II
c) III
d) IV
View Answer
Explanation: The sequences of the genes which appear in the mature or processed RNA are called as exons. They are the coding sequences of the gene. These sequences are interrupted by introns. Introns are the intervening sequences which aren’t present in both the mature or the processed RNA.
Sanfoundry Global Education & Learning Series – Biology – Class 12.
To practice all chapters and topics of class 12 Biology, here is complete set of 1000+ Multiple Choice Questions and Answers.
- Practice Class 12 - Mathematics MCQs
- Practice Class 12 - Physics MCQs
- Check Class 12 - Biology Books
- Practice Class 11 - Biology MCQs
- Practice Class 12 - Chemistry MCQs
