What happens when it goes wrong?

Question 1

What are mutations?

Answer 1

Mutations are randomly derived changes in the nucleotide sequences of the DNA of an organism

Question 2

What are the two types of mutations?

Answer 2

Somatic mutations and germ line mutations

Question 3

What are somatic mutations?

Answer 3

Occur in somatic cells and are passed on by mitosis but not to sexually produced offspring

Question 4

What are germ line mutations?

Answer 4

Occur in germ line cells, the cells that give rise to gametes and passes on mutation on fertilisation

Question 5

What are the different phenotypic effects of mutations?

Answer 5

Silent mutation; gain or loss of function mutations; conditional mutations

Question 6

What are silent mutations?

Answer 6

Neutral mutations that have no effect on amino acids

Question 7

What does the gain or loss of function mutations lead to?

Answer 7

Lead to a protein with new altered function or to a non-functional protein

Question 8

What are conditional mutations?

Answer 8

They cause phenotypes under restrictive conditions but are not detectable under permissive conditions

Question 9

What is a benefit of mutations?

Answer 9

Drive evolution in the form of genetic diversity

Question 10

What are large scale mutations?

Answer 10

Chromosomal mutations

Question 11

What do chromosomal mutations do?

Answer 11

May change the position or cause a DNA segment to be duplicated or lost

Question 12

What are small scale mutations?

Answer 12

Point mutations (as a result of the gain, loss or substitution of a single nucleotide)

Question 13

What can small scale mutations also lead to?

Answer 13

Insertion or deletions of one or a few bases

Question 14

What are the two types of point mutations?

Answer 14

Transition and transversion

Question 15

What are transition mutations?

Answer 15

Substitution of a purine by the other purine or of a pyrimidine by the other pyrimidine

Question 16

What are transversion mutations?

Answer 16

Substitution of a purine by a pyrimidine or vice versa

Question 17

In regulatory sequences for gene expression, what sort of mutation occurs?

Answer 17

Intron-exon borders (splicing)

Question 18

Describe silent mutations

Answer 18

They involve a base substitution at the 3rd position of the triplet codon and therefore causes no damage

Question 19

Describe missense mutations

Answer 19

They involve a base substitution that causes a change in the amino acid codon, which may or may not result in an altered function of the protein encoded by the gene

Question 20

Describe nonsense mutations

Answer 20

They involve a base substitution that causes a stop codon to form and this results in a shortened protein, which is usually not functional

Question 21

Describe readthrough mutations

Answer 21

They involve a base substitution that causes a stop codon to be converted into an amino acid codon and this results in a lengthened protein which might or might not be functional

Question 22

What amino acids are polar but with uncharged R groups due to missense mutations?

Answer 22

Serine, Threonine, Glutamine, Asparagine

Question 23

What amino acids have positively charged R groups due to missense mutations?

Answer 23

Lysine, Arginine, Histidine

Question 24

What amino acids have negatively charged R groups due to missense mutations?

Answer 24

Glutamic acid, Aspartic Acid

Question 25

What amino acids have hydrophobic R groups due to missense mutations?

Answer 25

Isoleucine, Leucine, Methionine, Phenylalaline, Tryptophan, Valine, Alanine, Tyrosine

Question 26

What are frameshift mutations?

Answer 26

These mutations interfere with the opening reading frame of a protein-coding gene

Question 27

What are the two ways a mutation can arise?

Answer 27

Spontaneous mutations and induced mutations

Question 28

How do spontaneous mutations occur?

Answer 28

Occur with no outside influence

Question 29

How do induced mutations occur?

Answer 29

Occur due to an outside agent

Question 30

What are the several mechanisms of spontaneous mutations that alter DNA?

Answer 30

Errors in replication by DNA polymerase that causes the wrong base to be inserted; bases can have different structures; chemical reactions may have change bases

Question 31

Describe the different ways an induced mutation can alter DNA

Answer 31

Base analogs (chemicals can alter base); some chemicals add other groups to bases and are DNA modifiers that cause structural changes to DNA; agents that act indirectly on DNA

Question 32

What are the deaminating agent of induced mutations?

Answer 32

Nitrous acid

Question 33

What do alkylating agents of induced mutations do?

Answer 33

They act directly on DNA causing mutations through mispairing or error-prone repair

Question 34

What are intercalating agents of induced mutations and what do they do?

Answer 34

Flat molecules that can slip between base pairs in the double helix, increasing the distance between adjacent bases, leading to structural distortions in the DNA

Question 35

What is the physical mutations of induced mutations?

Answer 35

Uv radiation is absorbed by thymine, causing it to form covalent bonds with adjcent thymine which disrupts DNA replication