Two different mutations are identified in a haploid stra...

Question

Two different mutations are identified in a haploid strain of yeast. The first prevents the synthesis of adenine by a nonsense mutation of the ade-1 gene. In this mutation, a base-pair substitution changes a tryptophan codon (UGG) to a stop codon (UGA). The second affects one of several duplicate tRNA genes. This base-pair substitution mutation changes the anticodon sequence of a tRNAᵀʳᵖ from

3′−ACC−5′ to 3′−ACU−5′

Do you consider the second mutation to be a forward mutation or a reversion? Why?

Accepted Answer

Hello everyone and welcome to today's video. So consider the following specific code in an M R N A sequence. Five prime C A G three prime, suppose this codon undergoes a nonsense mutation, which of the following coons can possibly result from this type of mutation. As answer choice A we have five prime C ac three prime B is five prime A, Eu G three prime C is five prime C A U three prime and D is five prime U A A three prime. Well, so in this problem, we have an M R N A sequence which is going to code for specific amino acid. And then we're told that this M R N A sequence is undergoing a nonsense mutation. Remember from previous videos that a nonsense mutation involves the creation of a stop coon. So a coon that's going to stop translation in the ribosome. So all we need to do to solve this problem is determine which one of these answer choices will create a stop codon. As it turns out there are three stop codons that we need to know. And these are U A A U A G N U G eight. So wherever the M R N A contains one of these coons translation will stop. And if we look at our answer choices, the only one present is U A A which is represented by answer choice D five prime U A A three prime this codon will create will be created from a nonsense mutation. I really hope this video helped you and I hope to see you on the next one.

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