Chapter 19 Key Words

Question 1

Mutation

Answer 1

A change in the sequence of bases in DNA. This change can be harmless, or it can have devastating consequences as it could disrupt protein synthesis.

Question 2

Substitution

Answer 2

One of the bases in the gene has changed. This could not have an effect as that base would still code for the same amino acid. However, a change in the amino acid that is coded for would change the primary structure of the polypeptide, and effect the subsequent protein.

Question 3

Frame Shift

(Insertion/Deletion)

Answer 3

Where a base is added or removed. this disrupts the whole sequence of codons after that new or removed base. this would result in a change of the polypeptide and the protein as a whole.

Question 4

Effects of Mutations:

No Effect

Answer 4

There is no effect on the phenotype and normally functioning proteins are still synthesised. These mutations can also be known as ‘silents’.

Question 5

Effects of Mutations:

Damaging Effect

Answer 5

The phenotype is affected in a damaging ways as proteins are no longer functional. This can interfere with vital processes.

Question 6

Effects of Mutations:

Beneficial Effect

Answer 6

The mutation improves chances of survival, is very rare, however. E.g, some have a mutation that means they cannot get infected by HIV.

Question 7

Causes of Mutations

Answer 7

They usually occur spontaneously, most often during DNA replication. The probability of this happening is raised in the presence of a mutagen. There are three types: physical mutagens, chemical mutagens and biological agents.

Question 8

Causes of Mutations:

Physical Mutagens

Answer 8

Ionising radiation - X-rays are an example. Break DNA strands, they are repaired, however, mutations can occur in this process.

Question 9

Causes of Mutations:

Chemical Mutagens

Answer 9

Deaminating agents - Chemically alters bases so that they are substituted. This changes the codon the mutation has occurred in.