Mutations

Question 1

Define mutations?

Answer 1

Defined as heritable changes in DNA

Question 2

Define somatic mutations

Answer 2

Occur in somatic (body) cells.
Mutations is passed to daughter cells, but not sexually produced offspring.

Question 3

Define germline mutations

Answer 3

Occur in cells that prod gametes
Can be passed to next generation

Question 4

What 2 scales con mutations occur?

Answer 4

Point mutations affecting just 1 or very few bases
Chromosomal mutations: affecting whole sections of chromosome (potentially 1000’s bases )

Question 5

What are point mutations?t

Question 6

What are silent mutations?

Answer 6

Have no effect on the protein because of the redundancy of genetic code

Question 7

Define missense mutations?

Answer 7

Base substitutions results in amino acid substitution
E.g.)s ickle cell disease
Defected sickle-shaped red blood ou

Question 8

Define nonsense mutations?

Answer 8

Base substitution results in a stop codon

Question 9

Define frame-shift mutation?

Answer 9

Single bases inserted or deleted → usually leadig to non-functional proteins

Question 10

Types of chromosomal mutations?

Answer 10

Deletions
Duplications
Inversions
Translocation

Question 11

Define deletion

Answer 11

DNA molecule breaks at 2 points and 2 pieces rejoin leaving out DNA between break
Severe consequences unless it affects unnescemry genes or it missing genes are mashed by normal alleles on a homologous chromosome

Question 12

Define dupli cation’s

Answer 12

Homologous chromosomes break in diff places and recombine with wrong patterns

May not be problem in original cell which still has 2 alleles for each gene but could cause problems in future generation as gametes formed by meiosis would pass on only one of these chrome comes

Question 13

Define inversions

Answer 13

Breaking and rejoining but A segment is flipped

May have no effect unless the break site happens in the middle of gene

Question 14

Define translocation

Answer 14

Segment of DNA break of f and is inserted into another non-homologous chromosome
Meiosis can be prevented as chromosome pairing may be impossible.

Question 15

Define s spontaneous mutations?

Answer 15

No outside influence
Tautomerisation
A temporary change caused by migration of an atom within the molecule
A problem if this happens during DNA replication → this rare tauter binds with an A
Cytosine → common tauter
2.) de animation
Bases may change →spontaneous chemical changes remove AA
1 in 100 c would change in human lifetime if - not repaired
3.) DNA replication errors
Some escape detection and repair by proofreading ability of DNA polymerase
4.) non-disjunction in meiosis

Question 16

Define induced mutation?

Answer 16

Due to an outside agent → a mutagen
Deamination
Chemicals such as nitrous acid (formed from nitrates)
Be laminated form of cytosine → uracil
2.) addition to bases
Benzopyrene → found in tobacco smoke adds a group to guanine and prevents base pairings
3.) ionising radiation
Ionising radiation con change bases break sugar phosphate bonds
4.) UV radiation is absorbed by thymine causing it to form covalent bonds with adjacent nucleotides

Question 17

What do mutations provide?

Answer 17

Often produce an organism less fit for the environment
Mutations con improve organisms adaptation to its environment or be come favourable as conditions change

Question 18

How does replication of gene expre’ssion in: prokaryotes takes place?

Answer 18

Usually a case of regulating transcription
RNA polymerase begins at a promoter where transaction is initiated
Selective gene transcriptions → a “descesion” is made about which genes will be transcribed

Question 19

What are the 2 types of gene expression?

Answer 19

Negative regulation
→ gene is normally transcribed ( usually” on”)
→ binding of a depressor protein prevents transcription
Positive regulation
→ gene is not normally transcribed ( usually “off”)
→ activator protein binds to stimulate transcription

Question 20

The lac open

Answer 20

?

Question 21

Try open

Question 22

Define Ind ucible system?

Answer 22

Control digestive /catabolic pathways
Turned Off when substrateis absent

Question 23

Define repressible system?

Answer 23

Control biosynthetic /anabolic pathways
(Turned off when productis present)