Question

1. Three mutations are listed below for the following mRNA at the positions they occur. Using the genetic code on page 304 of your text determine if the mutation causes a silent, missense or nonsense mutation.

5’ AUG GUC UCA GAC CGG UUA 3’

	Mutant 1 A in position 12
	Mutant 2 A in position 8
	Mutant 3 A in position 13

A.	nonsense
B.	silent
C.	missense

Answer 1

The given mRNA strand has the sequence of 5’ AUG GUC UCA GAC CGG UUA 3’

Mutant 1 - A in position 12

When A is put in position 12, GAC changes to GAA. This means GAC previously coding for Aspartic acid will now be coding for Glutamic acid (GAA). When mutation changes the type of amino acid being coded, this is called missense mutation.

Mutant 2 - A in position 8

When A is put at position 8, UCA changes to UAA. This means UCA previously coding for Serine will now be coding for Stop codon (UAA). When mutation changes the amino acid to a stop codon, this is called nonsense mutation.

Mutant 3 - A in position 13

When A is put at position 13, CGG changes to AGG. This means CGG previously coding for Arginine will now be coding for Arginine again. When mutation does not change the amino acid being coded, this is called silent mutation.

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