GENETICS AND EVOLUTION
MOLECULAR BASIS OF INHERITANCE
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Precursor of mRNA, hnRNA
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mRNA with additional processing, capping and tailing
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tRNA, 5 srRNA and snRNAs
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rRNAs-28 S, 18 S and 5.8 S
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Detailed explanation-1: -The genes for 18S, 5.8S, and 28S rRNA form a single transcription unit that is transcribed by RNA polymerase I to give a single large RNA (45S pre-rRNA). The extra eukaryotic 5.8S rRNA, which is absent in prokaryotes, lies between the 18S and the 28S rRNA.
Detailed explanation-2: -RNA polymerase I is devoted solely to the transcription of ribosomal RNA genes, which are present in tandem repeats. Transcription of these genes yields a large 45S pre-rRNA, which is then processed to yield the 28S, 18S, and 5.8S rRNAs (Figure 6.15).
Detailed explanation-3: -RNA polymerase I (Pol I) catalyses the transcription of all rRNA genes except 5S. These rRNA genes are organised into a single transcriptional unit and are transcribed into a continuous transcript. This precursor is then processed into three rRNAs: 18S, 5.8S, and 28S.
Detailed explanation-4: -The 5.8S, 18S, and 28S rRNAs are transcribed as a single unit within the nucleolus by RNA polymerase I, yielding a 45S ribosomal precursor RNA (Figure 8.22).