Shown below is the structure of a Drosophila gene, divided into 10 segments, des

Question

Shown below is the structure of a Drosophila gene, divided into 10 segments, designated A–J. The gene contains three exons, two introns, a promoter, and a site in I for poly(A) addition.

a) What segment or segments of the gene will be represented in the initial RNA transcript? List the appropriate letter or letters.
b) What segment or segments of the gene will be found in the completely processed transcript?
c) What segment or segments of the gene in the processed transcript will have additional nucleotides added to them?
d) What segment or segments of the gene contain the CCAAT box and TATA box elements?
e) What segment or segments of the gene will possess the translation initiation codon?
f) In a large sample of null alleles, would mutant sites be expected in segments C and D, at the boundary of G-H, or both? If mutant sites exist, would the transcript be detected? Would a polypeptide chain be observed?

Explanation / Answer

Answer:

(a) initial RNA transcript : C D, E, F, G, H, I

(b) completely processed transcript: C D, F, H, I, J

(c)additional nucleotides added to them: C, I .

(d) B, C

(e) D

(f) Mutant sites both in (C-D) and (G-H).

C: Transcripts might not be detected

D : Transcript may be detected for a null mutation in D,

polypeptide chain may be detected for a G-H mutation

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