7.1: mutagens

Question 1

variation meaning

Answer 1

genetic differences between individuals

Question 2

mutations

Answer 2

changes in genetic material of a cell; the altering of the sequence of nucleotides
- introduces new alleles into population
- can be spontaneous or due to environmental factors

Question 3

mutagens

Answer 3

environmental agents that alter DNA and cause mutations

Question 4

mutagenesis

Answer 4

the process of inducing a mutation, results in induced mutations

Question 5

mutagenesis examples

Answer 5

• marie curie + radiation = leukemia
• rosalind franklin + x-rays = ovarian cancer
• bombing of hiroshima + ionising radiation = physical mutation

Question 6

carcinogenic meaning

Answer 6

cancer-causing
- disrupts genes that regulate cell cycle + cell division

Question 7

two types of gene mutations that lead to cancer

Answer 7

1. proto-oncogenes
2. tumor suppressor genes

Question 8

chemical mutagens

Answer 8

chemicals which cause mutations if cells are exposed to them at high frequencies or for prolonged periods of time
- alters protein function, impairs cellular processes

Question 9

examples of two types of chemical mutagens

Answer 9

1. ingested chemicals: alcohol, tar in tobacco smoke, medications
2. environmental irritants and poisons: organic solvents, asbestos, pesticides

Question 10

structure of chemical mutagens

Answer 10

similar to purines + pyrimidines, incorporated accidentally into DNA during replication
- results in mispairing: insertion of incorrect nucleotides during replication, proteins don’t work

Question 11

naturally occurring mutagens

Answer 11

mutagenic agents that are present at normal levels in natural environments, likelihood of mutation increased with increased frequency + length of exposure

Question 12

two main groups of naturally occurring mutagens

Answer 12

1. biological mutagens: viruses, bacteria, fungi, their products
2. non-biological mutagens: metals, such as mercury and cadmium

Question 13

biological mutagens + their actions

Answer 13

• end-products of metabolism, produced during metabolism by fungi, or plant and animal cells; e.g. when certain foods are eaten together, will form carcinogenic mutagens when cooked at high temperatures
• transposons: sections of DNA that spontaneously fragment/relocate/multiply
• microbes: may alter genetic materials in cells; able to insert own sequences, products may cause inflammation and reduced efficiency of DNA repair systems, some products may be unstable at cellular pH and break down and bind to DNA to alter it

Question 14

physical mutagens

Answer 14

includes heat + ionising radiation
- heat: direct head combined with chemical/naturally occurring mutagens
- radiation: any transfer of energy through space from a source, ionising radiation has enough energy to break chemical bonds

Question 15

EM waves

Answer 15

shorter wavelengths included in ionising radiation
- e.g. shorter UV, x-rays, gamma rays

Question 16

UV

Answer 16

UVA(315-400): not ionising, prolonged exposure still bad
UVB(280-315) and UVC(180=280): ionising, causes chemical damage by breaking bonds, is mutagenic and carcinogenic

Question 17

ionising radiation

Answer 17

high-energy radiation that is able to free electrons from atoms/molecules
- turns electrons into ions, which react with water when passing through cells to release free radicals

Question 18

pyrimidine dimers

Answer 18

adjacent bases on the same strand attached
- most common effect of UV radiation rom sun on DNA

Question 19

free radicals

Answer 19

highly reactive, may act on other parts of cell
- results in: break of DNA strand, partial chromosome loss, rearrangements of sequences in DNA, cross-linking of DNA itself

Question 20

two main DNA repair mechanisms

Answer 20

1. base excision repair: damaged/incorrectly paired base removed from sugar linkage + replaced
2. mismatch repair: once DNA is replicated, polymerase carries out ‘spell check’ for accuracy