Chapter 9 Mutations

Question 1

Mutagens

Answer 1

Any agent capable of inducing a mutation e.g. UV radiation

Question 2

DNA replication errors - spontaneous mutations

Answer 2

-Occur in the absence of a mutagen
-Occurs in the synthesis phase of the cell cycle, when the DNA is unwound for replication and is exposed

Question 3

Disadvantageous mutations

Answer 3

harmful and cause pre mature death

Question 4

Beneficial mutations

Answer 4

helps with survival and allows organisms to produce more offspring

Question 5

Classification of mutations

Answer 5

1. Deleterious/harmful
2. Beneficial
3. Neutral

Question 6

Genotype

Answer 6

list of alleles

Question 7

Phenotype

Answer 7

Physical characteristics

Question 8

Allele

Answer 8

different versions of the same type of gene

Question 9

Mutations

Answer 9

-Change in the nucleotide sequence in DNA
-New alleles created, altering genotypes, -> sometimes alters phenotype

Question 10

DNA replication errors

Answer 10

-Spontaneous mutations
-Point mutations
-Frameshift mutations

Question 11

Point mutations

Answer 11

Affects a single base-pair position within a gene

Question 12

3 types of point mutations

Answer 12

1. Silent - no change to final amino acid
2. Missense - incorrect amino acid translated
3. Nonsense - a STOP codon is introduced

Question 13

Frameshift mutations

Answer 13

-Deletion or insertion of a single or non-multiple of 3 nucleotides into the DNA

Question 14

Damage to DNA by mutagens

Answer 14

Large accumulation of DNA damage by mutagens is often lethal to cells

Question 15

Damage to DNA by chemical mutagens

Answer 15

Substances that can alter a base that has already been incorporated into DNA and changing its hydrogen bonding specificity

Question 16

Damage to DNA by physical mutagens

Answer 16

Often caused by ionising radiation e.g UV, x-rays
-affect chemical structure
-cause deletion, creating gaps in double helix
-Break double stranded DNA

Question 17

Aneuploidy

Answer 17

The presence of an abnormal number of chromosomes in a cell
e.g human cell having 45 or 47 chromosomes instead of the usual 46

Question 18

non-disjunction

Answer 18

The failure of the chromosomes to separate, which produces daughter cells with abnormal numbers of chromosomes.

Question 19

Inherited mutations

Answer 19

-Somatic cell mutations not passed to offspring
-mutations in germline cells (produce gametes) are inherited passed to offspring