4.3: Genetic diversity - meiosis

Question 1

what happens to the number of chromosomes after meiosis occurs

Answer 1

number of chromosomes halves

Question 2

describe in a simple way the process of meiosis

Answer 2

2 consecutive divisions
Meiosis 1 - separation of bivalents producing 2 x n daughter cells
Meiosis 2 - separation of sister chromatids producing 4 x n daughter cells

Question 3

When does meiosis occur in the cell cycle and what happens

Answer 3

DNA replication - interphase

Question 4

describe what happens during meiosis 1

Answer 4

separation of bivalents producing 2 daughter cells, of which both are haploid and both contain one member of each bivalent

Question 5

describe what happens during meiosis 2

Answer 5

separation of sister chromatids producing 4 daughter cell of which all 4 are haploid and all contain one member of each homologous pair

Question 6

What happens during prophase 1 of meiosis 1

Answer 6

chromosomes condense and become visible arranged as bivalents

Question 7

What happens during prophase 2 of meiosis 2

Answer 7

chromosomes condense and become visible

Question 8

what is the difference in the way spindle fibres form during meiosis 2 and meiosis 1

Answer 8

spindle fibres form at right angle in meiosis 2 to the way they form in meiosis 1

Question 9

What happens during metaphase 1 of meiosis 1

Answer 9

bivalents align at equator of spindle

Question 10

What happens during metaphase 2 of meiosis 2

Answer 10

chromosomes align at equator of spindle

Question 11

What happens during anaphase 1 of meiosis 1

Answer 11

bivalents are separated

Question 12

What happens during anaphase 2 of meiosis 2

Answer 12

sister chromatids are separated

Question 13

what are the differences between mitosis and meiosis 2, during prophase, metaphase and anaphase

Answer 13

NO DIFFERENCES - TRICK QUESTION

Question 14

what are the differences between mitosis and meiosis 1, during prophase, metaphase and anaphase

Answer 14

bivalents in meiosis 1 instead of chromosomes in mitosis

Question 15

what is the main difference in importance between mitosis and meiosis

Answer 15

mitosis is for growth and repair
meiosis is for sexual reproduction

Question 16

what is the significance of meiosis (2 points)

Answer 16

1 - produces haploid gametes - important for when fertilising diploid number is restore
2 - produces genetic variation

Question 17

what are 3 ways in which meiosis can produce genetic variation

Answer 17

1 - random fertilisation
2 - independent segregation
3 - crossing over

Question 18

describe and explain how the random fusion of gametes produces genetic variation

Answer 18

each parent is genetically different, each parents produces 1000s of genetically unique gametes, at fertilisation the zygote has a unique combination of alleles

Question 19

describe and explain the process of crossing over in prophase 1 of meiosis

Answer 19

chromosomes condense and become visible as bivalents
chromosomes condense and tangle
non-sister chromatids cross over causing a chiasma to form
if the alleles for the genes at the chiasms are different, genetic info is swapped
each chromosome involved in crossing over then has a new combination of alleles not present in either parent, they are recombinant chromosomes -> genetic variation

Question 20

describe and explain the process of independent segregation/independent assortment/random assortment in metaphase 1 of meiosis and state what the number of possible chromosome combinations are in a human gamete

Answer 20

the separation of one pair of homologous chromosomes is independent of the separation of any other pair. This means that you can have multiple different possible chromosome combinations
In human gamete, there are 23 pairs, and so 2^23 = >8 million possible chromosome combinations

Question 21

how can you calculate the number of possible combinations of chromosomes in an organism’s haploid gamete, give an example

Answer 21

doves: 2n = 16 and so 8 pairs
2^8 = 256 possible combinations of chromosomes in their haploid gamete

Question 22

what is genetic diversity

Answer 22

the total number of different alleles in a population, the greater the number of different alleles, the greater the genetic diversity

Question 23

explain why genetic diversity is important

Answer 23

the greater the genetic diversity, the more likely that some individuals in a population will survive an environmental change.
this is because of a wider range of alleles and therefore a wider range of characteristics.
this gives a greater probability that some individuals will possess a characteristic that suits it to the new environmental conditions

Question 24

what would happen if we did not have genetic diversity

Answer 24

it would not be possible for natural selection to occur, therefore the species would be unable to evolve

Question 25

describe the term recombinant

Answer 25

a cell/organism whose genetic material was produced when segments of DNA from different sources are joined

Question 26

describe the term independent assortment

Answer 26

the random alignment of bivalents in metaphase 1

Question 27

describe the term homologous pair

Answer 27

2 chromosomes with the same gene loci

Question 28

describe the term non-diisjunction

Answer 28

the failure of homologous pairs to separate in meiosis

Question 29

describe the term crossing over

Answer 29

chromatids within a pair become twisted around one another when condensing in prophase 1

Question 30

describe the term bivalent

Answer 30

a pair of chromosomes with the same gene loci after DNA replication has occurred

Question 31

describe the term haploid

Answer 31

a cell/organism containing a single set of chromosomes

Question 32

state two locations in a mammal where meiosis takes place

Answer 32

testes (males)
ovaries (females)