Genetic Diversity

Question 1

Gene mutations involve a change in the ____ sequence of _________. They can arise spontaneously during DNA ________ and include base deletion and base substitution

Answer 1

base, chromosomes, replication

Question 2

What increases rate of mutation?

Answer 2

mutagenic agents

Question 3

what is silent substitution?

Answer 3

Due to the degenerate nature of the genetic code, not all base substitutions cause a change in the sequence of amino acids

Question 4

what is non-disjunction?

Answer 4

• failure of chromosomes to separate during anaphase

- produces abnormal no. of chromosomes

Question 5

give 2 examples of chromosome mutations

Answer 5

non-disjunction, polyploidy

Question 6

what is polyploidy?

Answer 6

• changes to whole sets of chromosomes

- have 3 or more sets of chromosomes rather than 2

Question 7

give an example of gene substitution

Answer 7

sickle cell anemia (1 nucleotide substitution in haemoglobin gene)

Question 8

Meiosis produces daughter cells that are…..

Answer 8

genetically different from each other

Question 9

which cells does meiosis occurs?

Answer 9

germline cells

Question 10

how many daughter cells are produced after 2 meiotic divisions?

Answer 10

4

Question 11

why is meiosis necessary?

Answer 11

halving of a diploid cell to become haploid by meiosis (allows the fusion of gametes via sexual reproduction)

Question 12

why are daughter cells genetically different?

Answer 12

independent segregation of homologous chromosomes

Question 13

when do homologous chromosomes separate during meiosis?

Answer 13

anaphase 1

Question 14

when do sister chromatids separate during meiosis?

Answer 14

anaphase 2

Question 15

how many chromosomes do daughter cells have after the second meiotic division?

Answer 15

23

Question 16

name the 3 things which increase genetic variation in offspring?

Answer 16

• independent segregation
• crossing over
• random fertilisation of haploid gametes

Question 17

describe crossing over

Answer 17

1. homologous pairs twist around each other
2. sister chromatids break + recombine to non-sister chromatid
3. broken portions exchanged between homologous chromosomes
4. new combinations of maternal/paternal alleles

Question 18

describe independent segregation

Answer 18

arrangement/combination of homologous pairs random in daughter cells (for both meiotic divisions)

Question 19

what is the formula to find the no. of possible combinations of chromosomes of maternal and paternal origin in its daughter cells as a result of MEIOSIS?

Answer 19

2^n (where n = no. of pairs of homologous chromosomes)

Question 20

what is the formula to find the no. of possible combinations of chromosomes in offspring after random FERTILISATION?

Answer 20

(2^n)^2 (where n = no. of pairs of homologous chromosomes)

Question 21

define genetic diversity

Answer 21

the no. of different alleles of genes in a population

Question 22

Genetic diversity is a factor enabling _______ ______ to occur

Answer 22

natural selection

Question 23

define natural selection

Answer 23

species better adapted to suit environment thru process of selection via environmental pressures

Question 24

The principles of natural selection in the evolution of populations.

1. Random mutation can result in new _____ of a gene.
2. Many mutations are harmful but, in certain environments, the new ____ of a gene might be beneficial = increased __________success.
3. The advantageous ____ is inherited by members of the next ________.
4. As a result, over many generations, the new ____ increases in ______ in the population.

Answer 24

1. allele
2. allele, reproductive
3. allele, generation
4. allele, frequency

Question 25

what are the 2 major factors in evolution + contribute to diversity of organisms?

Answer 25

adaptation and selection

Question 26

where does genetic diversity come from?

Answer 26

- change in quantity/structure of DNA (mutations) | - recombining DNA of 2 individuals after meiosis + binary fission

Question 27

Natural selection results in species that are.....

Answer 27

better adapted to their environment

Question 28

Adaptations may be..... (3 things)

Answer 28

anatomical, physiological or behavioural

Question 29

definition of polygenes

Answer 29

characteristics that are influenced by more than one gene

Question 30

effect of environment on _______ produces individuals within pop. that vary about the _____.

Answer 30

polygenes, mean

Question 31

what is directional selection?

Answer 31

- changes characteristics of pop. - favours/selections phenotypes at one extreme of pop. - distribution curve the same BUT mean shifts left or right - occurs when conditions aren't stable

Question 32

what is stabilising selection?

Answer 32

- preserves characteristics of pop. - favours/selects phenotypes around the mean - distribution curve becomes narrower/higher mean doesn't change - when environmental conditions are stable

Question 33

what happens to the distribution curve and mean of directional selection?

Answer 33

``` curve = remains same shape mean = shifts left or right ```

Question 34

what happens to the distribution curve and mean of stabilising selection?

Answer 34

``` curve = becomes narrower and higher mean = does not change ```

Question 35

is antibiotic resistance directional or stabilising selection?

Answer 35

directional

Question 36

how do antibiotics work?

Answer 36

1. H2O potential lower in bacteria cells = H2O enters via osmosis 2. meurin walls can't withstand pressure 3. osmotic lysis = zone of inhibition

Question 37

describe how there is penicillin resistant bacteria:

Answer 37

1. new allele of resistance 2. allele codes for penicillinase (active site complementary to antibiotic) = breaks down antibiotic 3. susceptible bacteria die, mutant bacteria are selected for 4. binary fission = pass on allele for resistance 5. frequency of that allele increases 6. distribution curve shifted in direction of pop. having greater resistance

Question 38

an example of stabilising selection

Answer 38

human birth weights - mortality rate are greater at 2 extremes (being selected against) - those around the mean less likely to die (selected for)