Genetic diversity can arise as a result of mutation or during meiosis

Question 1

What is a genetic mutation?

Answer 1

a change in the base sequence of DNA that can rise spontaneously during DNA replication

Question 2

What is a mutagenic agent?

Answer 2

a factor that increases the rate of gene mutation e.g. UV light or alpha particles

Question 3

How can a mutation lead to the production of a non-functional enzyme?

Answer 3

• changes the sequence of base triplets in DNA so changes codons on mRNA
• changes the sequence of amino acids in the polypeptide
• so changes the position of hydrogen/ionic/disulfide bonds
• so changes the tertiary structure of a protein
• enzymes - active site changes shape so enzyme-substrate complex can’t form

Question 4

What are the possible effects of a substitution mutation?

Answer 4

• DNA base is replaced by a different base
• this changes one triplet so changes one mRNA codon
• so some amino acid in the polypeptide chain changes - tertiary structure may change position of H/ionic/disulfide bonds
• or amino acid doesn’t change due to the degenerate nature of the genetic code where OR if mutation is in an intron so is removed by splicing

Question 5

What are the possible effects of a deletion mutation?

Answer 5

• one nucleotide is removed from the DNA sequence
• changes the sequence of DNA triplets from point of mutation
• changes sequence of mRNA codons after point of mutation
• changes sequence of amino acids in primary structure of polypeptide
• changes position of H/ionic/disulfide bonds so changes tertiary structure