Gene mutations

Question 1

Definition gene mutation

Answer 1

A change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide

Question 2

Definition mutagenic agents

Answer 2

Chemical, biological or physical agents that cause changes to the DNA of cell
e.g depurination leading to insertion of incorrect base through complementary base pairing during DNA replication

Question 3

Deletion

Answer 3

When one or more nucleotide bases are removed from a DNA sequence resulting in a frameshift, rendering the protein non-functional. (Non-overlapping nature)

Question 4

Substitution

Answer 4

When one nucleotide base is exchanged for another, which may change an amino acid or produce the same (degenerate nature of genetic code)

Question 5

Insertion

Answer 5

When one or more nucleotide bases are added to a DNA sequence resulting in a frameshift, changing every successive codon.(Non-overlapping nature)

Question 6

Point mutation

Answer 6

If only one nucleotide is affected

Question 7

Neutral effect

Answer 7

No effect on phenotype of an organism because normally functioning proteins are still synthesised.

Question 8

Damaging effect

Answer 8

Phenotype is affected in a negative way because proteins are no longer synthesised or proteins synthesised are non-functional which may interfere with one or more essential processes.

Question 9

Beneficial effect

Answer 9

New protein synthesis results in a useful characteristic in the phenotype. (Immunity from HIV by a protein embedded in the cell surface membrane means HIV cannot enter and bind)

Question 10

Chromosome mutations

Answer 10

Deletion-a section of chromosome breaks off and is lost within the cell
Translocation-a section of one chromosome breaks off and joins another non-homologous chromosome
Inversion-a section of chromosome breaks off, is reversed, and then joins back onto the chromosome