4. Genetic mutations cause genetic diversity

Question 1

Gene mutations

Answer 1

Gene mutations involve a change in the DNA base sequence of chromosomes. They can result in the formation of new alleles (forms of a gene). The types of errors that can occur include:
Substitution
Deletion

Question 2

Substitution

Answer 2

– a base is substituted in the DNA code
Original gene:
   G C T C A G A C G 
Mutated gene:
   G A T C A G A C G

Question 3

The effect of substitution mutations

Answer 3

Because of the degenerate nature of the DNA code…..
WHAT DOES THAT MEAN AGAIN?
Some amino acids have more than one triplet code
This means that not all substitutions result in a change in the primary structure (number and order of amino acid) of a polypeptide chain.

Question 4

Deletion

Answer 4

Deletion – removal of a base from the DNA code
Original gene:
   T A T A G T C T T 
Mutated gene:
  T A T    G T C T T

Question 5

The effect of deletion gene mutations

Answer 5

A deletion mutation causes a shift in the reading frame – called a frameshift so that every amino acid after the deletion (downstream of the deletion) will be affected.

Question 6

Chance and probability

Answer 6

The chance of something happening is the possibility that it will occur.
The probability is a measure of how likely events are to happen.
Key points:
There is always a chance of gene mutations occurring.
Under normal circumstances, the probability of a mutation occurring is very low.
The probability of a mutation occurring is increased by exposure to mutagenic agents.

MUTATIONS ARE ALWAYS RANDOM, JUST THE RATE IS AFFECTED BY MUTAGENIC AGENTS