8 - Gene mutations

Question 1

DNA damage

Answer 1

Physical abnormalities in DNA (e.g. single and double stranded breaks)

Question 2

Mutation

Answer 2

Change in the base sequence of the DNA

Question 3

Somatic mutation

Answer 3

Occur in non-reproductive cells and are passed to new cells through mitosis, creating a clone of cells with the mutant gene

Question 4

Germ line mutation

Answer 4

Occur in cells that give rise to gametes. Meiosis and sexual reproduction allow germ line mutations to be passed to half the members of next generation

Question 5

Which base pairs have 2 hydrogen bonds

Answer 5

A and T, C and G have 3

Question 6

Purine

Answer 6

Adenine and guanine (Pure As Gold). Larger due to two ring structure

Question 7

Pyrimidines

Answer 7

Cytosine, Thymine and uracil. Smaller due to single ring structure

Question 8

Base substitution

Answer 8

Changes the base of a single DNA nucleotide

Question 9

Transition

Answer 9

Base substitution in which a purine replaces a purine or pyrimidine replaces a pyrimidine

Question 10

Transversion

Answer 10

Base substitution in which a purine replaces a pyrimidine or a pyrimidine replaces a purine

Question 11

Insertion

Answer 11

Addition of one or more nucleotides, may lead to frameshift, usually alter all amino acids following the mutation

Question 12

Deletion

Answer 12

Deletion of one or more nucleotides, may lead to frameshift, usually alter all amino acids following the mutation

Question 13

Frameshift mutation

Answer 13

Insertion or deletion that alters the reading frame of a gene

Question 14

in frame deletion or insertion

Answer 14

Deletion or insertion of a multiple of three nucleotides that does not alter the reading frame

Question 15

expanding nucleotide repeats

Answer 15

Mutations in which number of copies of a set of nucleotides increases in number

Question 16

how can increases in repeat number cause
disease

Answer 16

• Nucleotide expands within coding part
  of gene, extra amino acid residues
  added, eg. Huntington disease
• Repeat may be outside coding region,
  but may affect gene expression, eg.
  Fragile X syndrome

Question 17

Forward mutation

Answer 17

Changes the wild-type phenotype to a mutant phenotype

Question 18

reverse mutation

Answer 18

Changes a mutants phenotype back to the wild type phenotype

Question 19

Missense mutation

Answer 19

The new codon encodes for a different amino acid. There is a change in amino acid sequence

Question 20

nonsense mutation

Answer 20

The new codon is a stop codon, there is a premature termination of translation

Question 21

silent mutation

Answer 21

New codon encodes the same amino acid, there is no change in the amino acid sequence

Question 22

Neutral mutation

Answer 22

Changes the amino acid sequence of a protein without altering its ability to function (chemically similar amino acid)

Question 23

Loss of function mutation

Answer 23

Causes complete or partial loss of function

Question 24

gain of function mutation

Answer 24

Causes the appearance of a new trait or function

Question 25

Lethal mutation

Answer 25

causes death

Question 26

suppressor mutation

Answer 26

Suppresses the effect of an earlier mutation at a different site

Question 27

Intragenic suppressor mutation

Answer 27

Suppresses the effect of an earlier mutation within the same gene by changing a second nucleotide in the same codon or suppressing a frameshift mutation

Question 28

Intergenic suppressor mutation

Answer 28

Suppresses the effect of an early mutation in another gene

Question 29

Depurination

Answer 29

Spontaneous chemical change that causes loss of purine base from nucleotide. Results when covalent bond connecting purine to 1’-carbon atom of deoxyribose sugar breaks. Produces apurinic site

Question 30

Deamination

Answer 30

Loss of amino group from a base. May be spontaneous or induced by mutagenic chemicals. Can alter pairing properties of a base

Question 31

Base analogs

Answer 31

Chemical mutagens with structures similar to that of the four standard bases. DNA polymerase cannot distinguish between these analogs.

Question 32

Pyrimidine dimers

Answer 32

Result from UV light, pyrimidine dimers are usually two thymine bases. Distorts DNA helix and blocks replication

Question 33

Phenotypic effects of mutations

Answer 33

• Forward mutation and Reverse mutation
• Neutral mutation
• Loss of function mutation
• Gain of function
• Conditional
• Lethal

Question 34

types of chemical changes

Answer 34

• Spontaneous chemical changes (depurination and deamination)
• Base analogs
• Pyrimidine dimers