Gene Mutations

Question 1

What are the types of gene mutation? (DADIT)

Answer 1

DELETION
-A base is removed from the base sequence
-This causes a frame shaft in the base sequence, affecting the entire polypeptide

ADDITION
-Extra base is added into base sequence
-This causes a frame shift of at least one

DUPLICATION
-One or more bases are repeated
-This also causes a frame shift of at least one

INVERSION
-A group of bases become separated from the DNA sequence
-They rejoin where they left but back to front

TRANSLOCATION
-Bases are removed from a section of DNA and inserted into another chromosome
-This significantly affects gene expression leading to a change in phenotype

Question 2

What are the three possible consequences of a substitution?

Answer 2

(1) The formation of one of the three stop codons (Stopping DNA coding prematurely)
(2) The formation of a codon for a different amino acid, resulting in a different amino acid forming, altering the polypeptide formed.
(3) Formation of a different codon that doesn’t alter the polypeptide coded for. This is due to the degenerate nature of the code.

Question 3

What are the causes of mutations?

Answer 3

-High energy ionising radiation

-Chemicals: Nitrogen dioxide alters the structure of DNA; Benzopyrene acts as a mutagen