Mutations

Question 1

Mutation

Answer 1

Hangs in nucleotide sequence that can be passed from one cell or organism to another

Question 2

Somatic mutation

Answer 2

Occur in body cells, passed to daughter cells in mitosis but not to offspring

Question 3

Germ line mutation

Answer 3

Occur in cells that give rise to gametes, passed to offspring at fertilisation

Question 4

Loss of function mutations

Answer 4

Gene not expressed at all, protein does not function, nearly always recessive

Question 5

Gain of function mutation

Answer 5

Produces protein with altered function, usually dominant, common in cancer

Question 6

Conditional mutation

Answer 6

Phenotype is altered but only under certain conditions, not detectable under permissive conditions

Question 7

Reversion mutations

Answer 7

Gene is mutated a second time and DNA reverts to original sequence or to a different sequence that results in non-mutant phenotype

Question 8

Point mutations

Answer 8

Insertion or deletion of a single base pair, or substitution of one base pair for another

Question 9

Transition point mutation

Answer 9

Purine mutated to other purine, pyrimidine mutated to other pyrimidine

Question 10

Transversion point mutation

Answer 10

Purine is substituted for a pyrimidine or a pyrimidine is substituted for a purine

Question 11

Silent mutation

Answer 11

Substitution that results in a codon that codes for the DMs amino acid

Question 12

Missense mutation

Answer 12

Substitution resulting in a different amino acid

Question 13

Nonsense mutations

Answer 13

Base substitution results in stop codon somewhere in mRNA

Question 14

Loss of stop mutation

Answer 14

Base pair substitution that changes a stop codon to a sense codon, extra amino acids are added to the polypeptide

Question 15

Frame shift mutation

Answer 15

Insertion or deletion of a base pair
Alters the mRNA reading frame during translation, produces nonfunctional proteins

Question 16

Promoter mutations

Answer 16

May alter rate of transcription in a gene

Question 17

RNA splice site mutations

Answer 17

May lead to abnormal mRNA

Question 18

chromosomal rearrangements

Answer 18

• DNA molecules can break and rejoin, grossly disrupting genetic sequences
• can be caused by damage to chromosomes by mutagens or errors, in chromosome replication

Question 19

deletion chromosomal rearrangement

Answer 19

• chromosome breaks into 2 places and rejoins, leaving out a part of DNA

Question 20

duplication chromosomal rearrangements

Answer 20

• homologous chromosomes break at different positions and reconnect to wrong partners
• also caused by inappropriate alignment of homologs during prophase 1, followed by crossing over

Question 21

inversion chromosomal rearrangement

Answer 21

• chromosome breaks & rejoins w/ one segment flipped

Question 22

translocation chromosome rearrangement

Answer 22

• segment of DNA breaks off & attaches to another chromosome, can cause duplications and deletions

Question 23

retroviruses

Answer 23

• insert DNA into host genome at random
• if insertion is within a gene, can cause loss of function mutation

Question 24

endogenous retrovirus

Answer 24

• viral DNA can remain in host genome and be passed from one gene to the next

Question 25

transposons

Answer 25

- insert themselves into genes & cause mutations - can move from one position in genome to another - short sequences can be left behind and become mutations

Question 26

spontaneous mutations

Answer 26

occur w/ no outside influence by several mechanisms - mistakes during replication - chemical reactions alter bases - meiotic errors

Question 27

induced mutations

Answer 27

agent form outside cell (mutagen) causes change in DNA - chemical mutagen can alter bases - some chemicals add other groups to the bases

Question 28

radiation induced mutations

Answer 28

- ionising radiation creates highly reactive free radicals - free radicals can change bases into forms not recognised by DNA polymerase - ionising radiation can also break sugar-phosphate bonds of DNA, causes chromosomal abnormalities

Question 29

benefits of mutations

Answer 29

- provides genetic diversity for natural selection - mutations in somatic cells may benefit an organism - in germ line cells, an advantageous change is passed onto offspring

Question 30

diseased effects

Answer 30

- in genes whose products are needed for normal cell processes, mutations are often deleterious, esp. in germ line cells - somatic cell mutations can be harmful = mutated oncogenes & tumour suppressor genes - mutations often expressed phenotypically as proteins that differ from normal proteins - abnormalities in enzymes, receptor/transport/structural proteins & others have been implicated in genetic diseases

Question 31

sickle cell disease

Answer 31

- mutations in HBB gene cause sickle cell disease - haemoglobin consists of 4 protein alpha-globin subunits and 2 beta-globin - 1 particular mutation of HBB produces an abnormal BG = sickle cell disease (HbS)

Question 32

mutations in somatic cells

Answer 32

- can lead to cancer - more than 2 mutations usually needed - mutations leading to each stage of colon cancer have been identified - 3 suppressor tumour genes & 1 oncogene must be mutated

Question 33

methods to detect & analyse mutations

Answer 33

- restriction enzymes - gel electrophoresis - DNA fingerprinting

Question 34

restriction enzymes

Answer 34

- cute DNA into small, non-infectious fragments - restriction enzyme breaks bonds between 3' hydroxyl group of one nucleotide and 5' of next - each type cuts DNA at a specific sequence - bacterial restriction enzymes can be isolated and used to identify DNA sequences of other organisms

Question 35

gel electrophoresis

Answer 35

- separates DNA fragments to identify where cuts are made - restriction sites not at regular intervals, so different size fragments gives 3 types of info: - no. of fragments - size of fragments - relative abundance, indicated by intensity of band

Question 36

DNA fingerprinting

Answer 36

- uses restriction enzymes & gel electrophoresis to identify individuals based on diffs in DNA - works best w/ high polymorphic sequences - having multiple alleles that are likely to differ between individuals

Question 37

single nucleotide polymorphisms

Answer 37

- inherited variations in a single base

Question 38

short tandem repeats

Answer 38

- short repetitive sequences, usually in noncoding regions, inherited