Genetic Mutations

Question 1

Diploid organism

Answer 1

• two sets of chromosomes
• two alleles of each particular gene
• mutations usually result in recessive alleles
• expressed only in the homozygous condition unless the mutation is on the X chromosome

Question 2

Homozygous

Answer 2

The two alleles are the same; the organism is homozygous for that gene

Question 3

Heterozygous

Answer 3

• the two alleles are different; the organism is heterozygous for that gene
• the dominant allele May mask the recessive gene

Question 4

If an organism is haploid (one set of chromosomes)

Answer 4

Recessive alleles are not masked by dominant alleles

Question 5

Genotype

Answer 5

Genetic composition of an organism

Question 6

Phenotype

Answer 6

Measurable physical and biochemical characteristics of an organism (whether desirable or not)

Question 7

Gene mutations

Answer 7

• changes in the nucleotide base sequence in a gene

* can result in non-functional proteins, including non-functional enzymes

Question 8

Types of gene mutations

Answer 8

• substitution
• deletion
• addition
• duplication
• inversion

Question 9

Substitution

Answer 9

• replacement of one nucleotide with another containing a different base
• missense

Question 10

Deletion

Answer 10

• loss of a nucleotide

Question 11

Addition

Answer 11

• aka insertion

* addition of an extra nucleotide

Question 12

Duplication

Answer 12

• repetition of a portion of a nucleotide sequence within a gene

Question 13

Inversion

Answer 13

• reversal of the portion of the nucleotide sequence in the gene

Question 14

Sickle cell anaemia

Answer 14

• inherited condition that results from a substitution

* RBC sickles in low O2 areas

Question 15

Mutations can be…

Answer 15

Disadvantageous, neutral or beneficial

Question 16

Disadvantageous mutations

Answer 16

• because DNA is non-overlapping
• frameshifts
• lack of a start codon/change in position
• codon changed into a stop codon (nonsense)

Question 17

Frameshifts

Answer 17

• addition and deletion

Question 18

Where do neutral mutations often occur?

Answer 18

In the introns

Question 19

Describe neutral mutations

Answer 19

• DNA is degenerate -> different codon but it codes for the same AA; protein structure is unaffected
• a different codon causes a different amino acid, but if it is not at an essential site on the polypeptide chain, it is possible that the change in amino acid could have no effect on protein structure
• think about where bonds form, and how this affects reactions and functions

Question 20

Beneficial mutations

Answer 20

• change the phenotype so the organism has a better chance of surviving and reproducing
• they are very rare, but inevitable in a population large enough
• ultimate source of all variation
• raw materials for the evolution of a new species by natural selection