Scenario 1 Slavko has high resting blood glucose levels. A DNA sample is taken f

Question

Scenario 1 Slavko has high resting blood glucose levels.

A DNA sample is taken from Slavko and the coding strand for a polypeptide, part of the glucose transporter is sequenced.

Slavko’s glucose transporter sequence is found to be slightly different from 99.9% of the population.

Below are the results: Common GLUT sequence: 5’ AGG CCT GAC TGT ATC AAT CTG ATC AAT GCG GGA ACG 3’

Slavko’s GLUT DNA sequence: 5’ AGG CCT GAC TGA ATC AAT CTG ATC AAT GCG GGA ACG 3’

a) During cell division, DNA undergoes replication. DNA is transcribed into mRNA and the genetic code is translated into a polypeptide sequence. Out of these three processes, which is most likely to be the site at which the mutation or alteration occurred? Explain why you have chosen this process.

b) Transcribe both of these DNA strands into mRNA.

c) Translate both of the mRNA strands using the codon table.

d) What is different about Slavko’s polypeptide sequence; what type of mutation is this? Are the number of base pairs altered? e) What impact would this altered DNA sequence have upon the polypeptide produced; do you expect any changes in the polypeptide? What type of mutation is this? f) Glucose normally interacts with the polypeptide at a site where there are Ala-Gly-Thr in sequence. Will glucose bind well to Slavko’s GLUT? What might you conclude about the effect of Slavko’s mutation on the function of the GLUT? In your view, could this mutation potentially explain Slavko’s high blood glucose levels? Why/why not?

Explanation / Answer

a) the site of alteration is replication process in which T is replaced with A.

normal DNA -

5’ AGG CCT GAC TGT ATC AAT CTG ATC AAT GCG GGA ACG 3’

Slavko’s DNA sequence:

5’ AGG CCT GAC TGA ATC AAT CTG ATC AAT GCG GGA ACG 3’

b) and c) normal DNA to mRNA -

5’ AGG CCU GAC UGU AUC AAU CUG AUC AAU GCG GGA ACG 3’

protein sequence - R P D C I N L I N A G T

Slavko’s DNA to mRNA -

5’ AGG CCU GAC UGA AUC AAU CUG AUC AAU GCG GGA ACG 3’

protein sequence - R P D & (termination)

d) this is a nonsense mutation. no frameshift mutation.

e) the polypeptide is not fully formed and terminated abruptly. this is a transversion (conversion of T to A) and nonsense (UGU to UGA) mutation.

f) since there is no AGT sequence present in GLUT of Slavko's, so no glucose will bind to the receptor and transported. this is a reason for the high sugar level.

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