Gene mutationsEdexcel International A Level Biology: Flashcards

What these 12 flashcards ask

What is a gene mutation?
How do mutations arise during replication?
What is a substitution?
What is an insertion?
What is a deletion?
What is a frameshift?
Why might a substitution have no effect on the polypeptide?
Why is a deletion of three bases often less harmful than a deletion of one?
How can a substitution shorten a polypeptide?
Name a genetic disorder caused by a substitution.
How can a mutation lead to cancer?
Give two reasons why a mutation may have no observable effect.

Exam questions on Gene mutations

In sickle cell anaemia, a change in the gene for the beta chain of haemoglobin alters one codon in the mRNA from GAG, which codes for glutamic acid, to GUG, which codes for valine. All the other codons are unchanged.
Explain how this change in one codon can alter the properties of the haemoglobin protein.2 marks
The mRNA of a gene has the codon sequence AUG GCA UUC GAA UAA. A mutation deletes the first base of the second codon, the G of GCA, and the rest of the mRNA is unchanged.
Explain why deleting three consecutive bases from the middle of a gene may be less harmful than deleting a single base.2 marks
In an mRNA, the codon GAA codes for glutamic acid. The codon GAG also codes for glutamic acid, the codon GAU codes for aspartic acid and the codon UAA is a stop codon.
Describe and explain the effect on the polypeptide of a substitution that changes the codon GAA to (i) GAG, (ii) GAU and (iii) UAA.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).