Question

8) You have extracted DNA from two different organisms. In the purification process, you find that the two test tubes have lost their identifying labels. The sequences of DNA are:

Sample 1: TCC CTA TGC CCG ///// AGG GAT ACG GGC

Sample 2: CGA TCT TAA CCC ///// GCT AGA ATT GGG

The only other piece of information you have is the corresponding amino acid sequence of a particular protein for both organisms. Organism I has ala-arg-ile-gly and organism II has ala-arg-ile-pro.

a) What amino acid sequence corresponds with which nucleic acid sequence?

b) For each sample of DNA, which is the sense strand?

Answer 1

(a)

Sample I with sequence 5'-gcc cgt atc cct-3' codes for "ala-arg-ile-pro". Hence sample I belongs to organism II.

Sample II with sequence 5'-GCT AGA ATT GGG-3' codes for "ala-arg-ile-gly". Hence sample II belongs to organism I.

(b) Sense strands are

3'-TCC CTA TGC CCG-5' (sample I).

5'-GCT AGA ATT GGG-3' (sample II).