Mutations

Question 1

Define mutation

Answer 1

Change in DNA which can result in a non functioning protein being formed
Also may provide advantages to the organism

Question 2

What is a gene mutation?

Answer 2

A change to one or more nucleotide bases, or a change in the sequence of the bases in DNA
Can arise spontaneoulsy during DNA replication

Question 3

What makes a random mutation more likely to happen?

Answer 3

Exposure of DNA to mutagenic agents which interfere with DNA replication such as UV light, ionising radiation and chemicals

Question 4

What can a gene mutation result in a DNA sequence?

Answer 4

A base substitution mutation
A base deletion mutation

Question 5

What can cause a base sequence mutation to be silent?

Answer 5

-The new codon( the result of base substitution or deletion) may code for the same amino acid as the previous codon
- This is due to the genetic code being degenerate, more than one codon can code for the same amino acid

Question 6

Why might a base deletion of a DNA sequence be more impactful than substitution

Answer 6

• Base deletions result in a frame shift, as the removal of one base changes all the subsequent codons
• This means more amino acids may be incorrectly coded for meaning the polypeptide chain is completley different

Question 7

What may mutation in chromosome number be caused by?

Answer 7

• Chromosome non disjunction during meosis
• This is when the chromosome or chromatid do not separate equally during anaphase
• This results in a gamete having one fewer chromosome or one more chromosome

Question 8

How can a chromosome mutation result in changes in whole sets of chromsomes?

Answer 8

Occor when organisms have 3 or more sets of chromosomes rather than the usual 2
This is polypioldy often happens in plants

Question 9

Describe what non disjunction means

Answer 9

Chromatids fail to seperate during anaphase
Causing both chromatids to go to one pole of the cell

Question 10

Define gene mutation

Answer 10

Change in the base sequence of DNA

Question 11

Why might a mutation have no effect on an indivdual

Answer 11

Genetic code is degenerate so the amino acid sequence may not change, new codon might code for the same amino acid
-Mutation may be in an intron
-Might change the amino acid sequence but has no effect on tertiary structure
- New allele is recessive so has no effect on phenotype

Question 12

Why may a mutation have a positive effect on an indivdiual

Answer 12

Results in a change in the polypeptide chain that has a positive effect on the properties of the protein
May result in a phenotype better suited to the enviroment, increased reproductive sucess