A long RNA molecule contains only the bases adenine and uracil in equal amounts

Question

A long RNA molecule contains only the bases adenine and uracil in equal amounts and in random order. Assuming that this RNA can be translated to make a protein, what are the possible amino acids that can be found in the protein? You have discovered a gene (Figure 1) that is alternatively spliced to produce several forms of mRNA in various cell types, three of which are shown in Figure 1. The lines connecting the exons that are included in the mRNA indicate the splicing. From your experiments, you know that protein translation begins in exon 1. For all forms of the mRNA, the encoded protein sequence is the same in the regions of the mRNA that correspond to exons 1 and 10. Exons 2 and 3 are alternative exons used in different mRNA, as are exons 7 and 8. Which of the following statements about exons 2 and 3 is the most accurate? Explain your answer.

Explanation / Answer

1. Leucine and isoleucine can be found in that RNA coded protein, but the sequence of amino acids is purely based on nucleotides arrangement that was not shown here. Hence, these 2 amino acids could repeat randomly.

2. D might be the right answer.

3a. If bottom strand is template, that is shown in 3'----->5' direction, the transcription starts at 11th nucleotide, So, the new RNA starts in 5'--->3' direction with complementary sequence as AAA CAG CUA UGG CCA UGA GCC CUC AUU ACA

3b. From above RNA, the first 6 amino acids are K-Q-L-W-P-Opal terminator (UGA- codes for no amino acid) as per genetic code rules.

3c. No, before that 'TAA' of DNA template, there is a terminator codon in complementary mRNA that does not allow to extend further as shown in 'b'.

3d. K-Q-L-W-Q-Opal terminator, here, the 5th amino acid proline was replaced by gutamine why because the CCA, which codes for proline (P) was altered into CAA that codes glutamine (Q). Third base change is may not cause such a great difference in all the cases, but changes in 1 and 2 bases of nucleotide leads to drastic variation in protein composition by varying amino acids

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