KA : 1.6 Mutations

Question 1

What are mutations?

Answer 1

Mutations are a change in the structure or amount of an organism’s DNA. Mutations can be the result of very small changes to the DNA or huge changes to an entire chromosome. Mutations arise spontaneously and at random.

Question 2

What is the mutation rate of a gene?

Answer 2

The mutation rate of a gene is the number of mutations that occur at a gene site per million gametes.

Question 3

Single gene mutations involve…

Answer 3

Involve a change in one of the base pairs in the DNA sequence of a single gene.

Question 4

Substitution

Answer 4

A single nucleotide is replaced with another base.

Question 5

Insertion

Answer 5

An extra nucleotide added.

Question 6

Deletion

Answer 6

Nucleotide removed.

Question 7

What are the 3 single nucleotide substitutions?

Answer 7

• Missense mutations
• Nonsense mutations
• Splice-site mutations

Question 8

What are Missense mutations?

Answer 8

• The substituted nucleotide results in a triplet that codes for a different amino acid.
• This change in amino acid could could change the function of the protein but usually doesn’t alter the effect.

Question 9

What are Nonsense mutations?

Answer 9

• The substituted nucleotide results in a stop codon meaning the polypeptide chain is shorter.
• This change in the chain size will either not form a functioning protein ot will form a different protein.

Question 10

What are Splice-site mutations?

Answer 10

• Either inserts, deletes or changes a number of nucleotides in the specific site at which splicing takes place to lead to creating the mature mRNA transcript.
• This will lead to a creation of a protein that does not function properly.

Question 11

“Nucleotide insertions or deletions result in a ____-___ mutation”

Answer 11

Nucleotide insertions or deletions result in a frame-shift mutation.

Question 12

What are Frame-shift mutations?

Answer 12

• The result of deletion or insertion.
• Entire sequence if triplets after this point will be different.
• Meaning every base is in the wrong place and the sequence of amino acids will be changed.

Question 13

What are the 4 main types of chromosome structure mutation?

Answer 13

• Duplication.
• Deletion.
• Inversion.
• Translocation.

Question 14

Change in chromosome structure = a change…

Answer 14

A change in the number or sequences of genes in a chromosome.

Question 15

What is a Duplication mutation?

Answer 15

• When a segment of homologous
  chromosome becomes attached to its
  partner or inserted somewhere along its length.
• This results in a set of genes being repeated.

Question 16

What is a Deletion mutation?

Answer 16

• Chromosome breaks in 2 places, a
  segment becomes detached, the two
  ends join up giving a shorter chromosome which lacks certain
  genes.
• This results in drastic effects in the organism as many genes are lost.

Question 17

What is an Inversion mutation?

Answer 17

• Chromosome breaks in 2 places and flips before joining up again.
• This causes the reversal of the normal sequence of genes.

Question 18

What is a Translocation mutation?

Answer 18

• When one section of a chromosome breaks off and becomes attached to another chromosome, which is not its homologous pair.
• This results in problems with homologous chromosome pairings during meiosis, resulting in non-viable gametes.

Question 19

What is the evolutionary importance if mutation and gene duplication?

Answer 19

Duplication allows potential beneficial mutations to occur in a duplicated gene whilst the original gene can still be expressed to produce its protein.