(9) Genetic Diversity

Question 1

define mutation

Answer 1

changes to the base sequence in dna

can be caused by addition, deletion and substitution of bases

Question 2

what is an addition mutation

Answer 2

when one or more bases is added to the dna sequence

Question 3

what is a deletion mutation

Answer 3

where one or more bases is removed from the dna sequence

Question 4

what is a substitution mutation

Answer 4

where one or more bases is changed in the dna sequence

Question 5

what are causes of mutations

Answer 5

1) errors in the replication process when the bases in the dna sequence are read and copied
2) mutagenic agents which increase the rate at which mutations occur and include chemicals and radiation exposure
3) chromosome mutations- arise spontaneously during meiosis (when chromosomes don’t separate properly)

Question 6

what is a non disjunction mutation

Answer 6

mutations in the number of chromosomes in the cell

Question 7

how does a non disjunction mutation result in down syndrome

Answer 7

extra copy of chromosome 21

can cause heart defects, shorter lifespan and development of alzheimers

Question 8

what is meiosis

Answer 8

the process which produces haploid gamete cells from diploid cells in an organism

Question 9

what are the 2 ways that genetic variation is generated in each daughter cell in meiosis

Answer 9

1) the chromosomes of a homologous pair are arranged down the middle of a cell before meiosis 1. Sections of dna are swapped between the chromosomes in a process called crossing over which produces new combinations of alleles
2) chromosomes in homologous pairs are separated and combined randomly which is called independant segregation

Question 10

how is genetic diversity in a population increased

Answer 10

1) mutations (creation of new alleles)

2) Gene flow (introduction of new alleles by migration)

Question 11

define evolution

Answer 11

A change in allele frequency over time

Question 12

what is a selection pressure

Answer 12

an external factor that influences the reproductive success of an individual eg disease acts as a selection pressure that increases the reproductive success for individuals who are immune

Question 13

what is stabilising selection

Answer 13

selection where individuals with alleles for characteristics towards the middle of the range are more likely to survive and reproduce
occurs when the environment is non changing and reduces the range of possible characteristics

Question 14

what is directional selection

Answer 14

where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce eg in response to an environmental change

Question 15

what is an anatomical adaptation

Answer 15

physical structures that have evolved to increase the chance of survival

Question 16

what is a physiological adaptation

Answer 16

processes within the body which have evolved to increase the chance of survival eg shivering

Question 17

what is a behavioural adaptation

Answer 17

actions that have evolved to increase the chance of survival eg spider building a web

Question 18

what are 3 ways to make the conditions aseptic when preventing contamination of microbial cultures

Answer 18

1) disinfect surfaces
2) sterilise equipment to destroy microorganisms
3) Flame the necks of bottles on opening

Question 19

why should the lid of the petri dish be secured loosely with tape

Answer 19

allows the flow of oxygen and so prevents any anaerobic bacteria from growing

Question 20

why is mRNA produced more quickly in prokaryotic cells than eukaryotic

Answer 20

because it doesn’t have to be disassociated from histones and doesn’t have to undergo splicing to remove introns