Question

You identify a gene from E. coli that is very small. Using recombinant DNA technology, you managed to clone the whole piece of DNA that contains all codons (including stop and start codons) for protein synthesis. Using automated sequencing, you obtain the following sequence:

5’-TTAATATCAAGCTGATTCAGGCCCAAACATCCT-3’

A. Using the above sequence for reference, write out the mRNA transcript (be sure to label the 5' and 3' ends).

B. Translate the protein that is coded for by the mRNA strand.

C. How many amino acids are in this protein?

D. How many codons code for this protein?

Answer 1

Answer:

A). First we need to writ the DNA from 3’ to 5’ which is the sequence of DNA template. Write in reverse order.

DNA template= 3’ TCCTACAAACCCGGACTTAGTCGAACTATAATT – 5’

mRNA = 5’ – AGGAUGUUUGGGCCUGAAUCAGCUUGAUAUUAA – 3’

B).

Translation starts from AUG codon, which is the first codon of mRNA.

Final mRNA = 5’– AUGUUUGGGCCUGAAUCAGCUUGAUAUUAA – 3’

Amino acids = Met – Phe –Gly – Pro – Glu – Ser – Ala-STOP

C). Seven amino acids are present in the protein

D). Seven codons code for this protein.