6.1 - Cellular Control

Question 1

What is an exon?

Answer 1

Coding part of a gene.

Question 2

What is an intron?

Answer 2

Non-coding part of a gene.

Question 3

Why is the term ‘junk’ DNA misleading?

Answer 3

Junk implies this DNA has no function – in truth we do not yet know the function.

Question 4

What is a mutation?

Answer 4

A change to the base sequence.
Substitution: One or more bases are swapped for one another.
Deletion: One or more bases are removed.
Insertion: One or more bases are added.

Question 5

How might a deletion of bases mutation affect protein functionality?

Answer 5

Deletion leads to frameshift. Changes amino acid sequence. Affects hydrogen/ionic/sulphur bonds. Changes tertiary structure of protein – so cannot function.

Question 6

How might a mutation result in a non-functional protein?

Answer 6

Mutation causes a stop codon so transcription stopped prematurely. Mutation codes for a different amino acid to be produced - protein may/may not function.

Question 7

When may a mutation not result in a non-functional protein?

Answer 7

Mutation codes for same amino acid to be produced due to the degenerate nature of the genetic code. Mutations that occur in the non-coding DNA regions – the introns will be removed by splicing & not be translated so have no effect on protein produced.

Question 8

What are the causes of mutations?

Answer 8

Spontaneous during DNA replication. Mutagens - Chemicals that alter the DNA structure or high energy radiation.