Shown is a primary RNA transcript that is made by RNA polymerase. The size the e

Question

Shown is a primary RNA transcript that is made by RNA polymerase. The size the exons and the space between exons in the figure is proportion to the number of nucleotides in each segment. The reading frame of Exon 1 is only maintained when it is spliced to Exon 2. Any other splicing with Exon 1 results in a non-functional protein. Exons 2, 3, and 4 all have the same reading frame. Only Exon 3 and Exon 4 contain a stop codon. The nucleotides represented between the exon boxes are called ________ and they ______. A) introns: are made of junk DNA B) spacers: are made of amino acids C) mRNA: regulate translation rates D) genes: bind ribosomes E) introns: do not code for amino acids There is only one MET amino acid coded for in this transcript. How many different mRNAs can be made that code for a functional protein by splicing this primary RNA transcript? A) 1 B) 2 C) 6 D) 9 E) There is not enough information to determine. Suppose that splicing occurs normal and the mRNA that is formed codes for a functional protein with the most amino acids that is possible from the gene. During translation, which exon would be translated immediately following Exon 2? A) Exon 1 B) Exon 3 C) Exon 4 D) Both B and C can be correct. E) There is not enough information to determine.

Explanation / Answer

Answer:

22. (E) The nucleotides represented between the exon boxes are called introns and they do not code for amino acids.

Explanation:

Introns are non coding sequences of an RNA transcript and are spliced out during the formation of a mature mRNA.

23. (B) 2

Explanation:

For encoding a functional protein, the exons can join in the following way to form the transcripts:

i. Exon 1 - Exon 2 - Exon 3

ii. Exon 1 - Exon 2 - Exon 4

So, two different mRNAs can be formed through splicing which can code for functional proteins.

24. (C) Exon 4

Explanation:

Exon 4 is longer than Exon 3. So, the combination of Exon 1 - Exon 2 with Exon 4 (i.e, Exon 1 - Exon 2 - Exon 4) would yield a protein with most amino acids.

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