MOD 6 - Genetic Change

Question 1

mutagen

Answer 1

an external agent that induces a genetic mutation

Question 2

mutation

Answer 2

a change in the nucleotide sequence of an organism’s genome

Question 3

allele

Answer 3

1 OF two or more versions of a genetic sequence/gene at a particular locus on a chromosome
- consisting of a different base sequence

Question 4

carcinogenic/carcinogens

Answer 4

carcinogen - cancer causing mutagens

Question 5

types of mutations

Answer 5

1. physical - ionising
2. chemical
3. naturally occuring - biological, non-biological

Question 6

chemical mutagens

Answer 6

chemicals that cause mutations if cells are exposed to them at high frequencies for extended periods of time

Question 7

effect of chemical mutagen

Answer 7

• changes to DNA that alter the function of proteins (following DNA transcription) -> metabolic processes are impacted.

Question 8

types of chemical mutagen

Answer 8

1. intercalating agents
2. base analogues
3. DNA reactive chemicals

Question 9

intercalating agents - mechanism of the mutation formation

Answer 9

• insert between base pairs and alters shape of DNA
• leads to errors in DNA replication -> due to inducing frameshift mutations

Question 10

intercalating agent - example

Answer 10

thalidomide - anti morning sickness drug for preggos in 1950s

• induced mutations in foetus -> birth defects

Question 11

base analogues

example:

Answer 11

• compounds structurally similar to nitrogenous bases
• misplace bases and are incorporated into DNA during replication

THEREFORE -> non-functional DNA

fluorescent di-deoxynucleotides - terminates elongation of DNA chains

Question 12

DNA reactive chemicals

example

Answer 12

• react directly with the molecules that constitute DNA
• cause breakages or cross-links -> disrupts replication and base pairing

eg. reactive oxygen species like Hydrogen Peroxide

Question 13

physical mutagens

Answer 13

• involve ionising radiation e.g. electromagnetic radiation
• effect:
  1. change chemical structure of DNA
  2. cause bonds to appear in wrong locations
  3. break bonds, electrons split away

Question 14

ionising radiation

Answer 14

• wavelengths higher than 315nm
• UV - UVB & UVC - shorter wavelengths
• xrays
• gamma rays
• high energy electrons = free radicals

Question 15

UV - ultraviolet light

Answer 15

source: sun
types:
1. UVA - 315-400nm
2. UVB - 280-315nm
3. UVC - 160-280nm

• contributer to skin cancer

effect:
* produce pyrimidine dimers

Question 16

pyrimidine dimers

Answer 16

• double bonded DNA bases - thymine & cytocine
• when two adjacent DNA bases on same strand bond w each other instead of w complimentary base

Question 17

e.g. thymine dimer

Answer 17

1. forms kink in backbone - bending
2. disrupts enzyme reading of DNA
3. mutation in newly synthesised DNA

Question 18

naturally occuring mutagens

Answer 18

• can drive evolution and new adaptations
• exist in enviroment at normal levels
• e.g. cycad fruits - cycasin mutagenic

Question 19

naturally occuring mutagens

nitrosamines & processed meat

Answer 19

nitrosamines - chemicals released in stomach as product of metabolism between nitrates and amines
- produced and released in stomach

e.g. smoked and processed meat - high conc. of nitrates and amines
- cooking forms nitrosamines -> carcinogenic

Question 20

point mutation

Answer 20

cause: single nucleotide base is:
- changed
- inserted
- deleted

effect: base pair substituion OR frameshift mutation

phenotypic effect:
- completely unnoticeable
- severe diseases = dysfucntional proteins