Question

You are looking at three alleles of the same gene. The mRNA derived from them is shown below.

Allele 1 - AUUCCCAUGACCCCCCCCUGA

Allele 2 - CCCAUGACCCAUUAAAUCCCC

Allele 3 - AUGACCCAUUAUAUCCCCUGA

Rearrange the boxes below to place the alleles in the correct order with respect to the size of the polypeptide encoded. Largest on the top, smallest on the bottom.

You may need a codon table to answer this question. You can find one here.

Allele 3

Allele 1

Allele 2

Answer 1

The start codon of the translation process will be always 'AUG' coding for the amino acid methionine. The process of protein synthesis terminate when the ribosome encounter any of the three stop codons 'UAA', 'UGA' nd 'UAG' of the mRNA.

Allele 1:

In allele 1 the coding region of the mRNA sequence is highlighted, which is starting with AUG and terminate with the stop codon UGA.

Allele 1 - AUUCCCAUGACCCCCCCCUGA

The polypeptide from this sequence will be Met (from AUG codon), Thr (from ACC codon), Pro (from CCC codon), Pro (from CCC codon).

The polypeptide from allele 1 is MTPP.

Allele 2:

In allele 2, the coding region of the mRNA sequence is highlighted, which is starting with AUG and terminate with the stop codon UAA.

Allele 2 - CCCAUGACCCAUUAAAUCCCC

The polypeptide from this sequence will be Met (from AUG codon), Thr (from ACC codon), His (from CAU codon).

The polypeptide from allele 2 is MTH.

Allele 3:

In allele 3, the given mRNA sequence represent the coding region starting with AUG and terminate with the stop codon UGA.

Allele 3 - AUGACCCAUUAUAUCCCCUGA

The polypeptide from this sequence will be Met (from AUG codon), Thr (from ACC codon), His (from CAU codon), Tyr (from UAU codon), Ile (from AUC codon), Pro (from CCC codon).

The polypeptide from allele 2 is MTHYIP.

The allele 3 codes for the longest polypeptide, allele 1 codes for the second longest polypeptide and the shortest polypeptide is coded by allele 2.

The following is the correct order of the allele with respect to the size of the polypeptide encoded.

Allele 3 - AUGACCCAUUAUAUCCCCUGA

Allele 1 - AUUCCCAUGACCCCCCCCUGA

Allele 2 - CCCAUGACCCAUUAAAUCCCC