4.3 Genetic diversity

Question 1

What does meiosis produce?

Answer 1

Haploid gametes - genetically different

Question 2

Where does meiosis take place?

Answer 2

Sex organs

Question 3

Why is it important that gametes are haploid?

Answer 3

So they can fuse together during fertilisation forming a diploid zygote

Question 4

What is a chiasmata?

Answer 4

The point where the chromosomes join during crossing over

Question 5

What is the full sequence of meiosis?

Answer 5

Interphase
Meiosis 1
Cytokinesis 1
Meiosis 2
Cytokinesis 2

Question 6

What happens to the chromosomes during meiosis?

Answer 6

The no. Of chromosomes in each cell produced is decreased by half

Question 7

What happens during meiosis 1?

Answer 7

Separation of bivalents
Produces 2 haploid daughter cells

Question 8

What happens during meiosis 2?

Answer 8

Separation of sister chromatids
Produces 4 haploid daughter cells

Question 9

What happens during prophase 1 in meiosis 1?

Answer 9

The chromosomes condense and become visible arranged as bivalents
The nuclear membrane breaks down
Spindle fibres same as mitosis

Question 10

What happens during metaphase 1 of meiosis 1?

Answer 10

The bivalents align at the equator of the spindle apparatus

Question 11

What happens during anaphase 1 of meiosis 1?

Answer 11

Spindle fibres shorten
Bivalents move to opposite poles - chiasmata break

Question 12

What happens during prophase 2 of meiosis 2?

Answer 12

Chromosomes condense and become visible again
Nuclear membrane breaks down
Spindle fibres develop

Question 13

What happens during metaphase 2 of meiosis 2?

Answer 13

The chromosomes are aligned on the equator or the spindle apparatus

Question 14

How do the chromosomes align on the equator differently in meiosis 2 to meiosis 1?

Answer 14

The chromosomes align at right angles during meiosis 2 to the way they were aligned in meiosis 1

Question 15

What happens in anaphase 2 in meiosis 2?

Answer 15

The centromere of each chromosome divides and the sister chromatids are separated
Spindle fibres shorten

Question 16

What does it mean that meiosis is reduction division?

Answer 16

The no. Of chromosomes half

Question 17

How does meiosis increase genetic diversity?

Answer 17

Crossing over
Random fusion of gametes
Independent segregation

Question 18

How do you calculate the number of genetically different gametes produced by independent segregation?

Answer 18

2 to the power of n
Where n is the no. Of homologous chromosome paira

Question 19

What is random fusion of gametes?

Answer 19

Lots of genetically different gametes produced
We cannot predict which male gamete will fuse with which female gamete- random fusion

Question 20

How does random fusion of gametes create genetic diversity?

Answer 20

each parent is genetically different
produces gametes which have a unique combination of alleles
fertilisation = the zygote has an unique combination of alleles

Question 21

How does crossing over happen?

Answer 21

chromosomes condense and tangle during Prophase 1
they cross over to form Chiasmata - the genetic info is swapped if chromosomes are heterozygous
each chromosome then has a new combination of alleles - recombinant chromosomes

Question 22

What are recombinant chromosomes?

Answer 22

the new combination of alleles after crossing over are not present in either pair of parent chromosomes

Question 23

What is independant segregation?

Answer 23

The random separation of homologous chromosomes in meiosis 1 that produces genetic variation

Question 24

How do the chromosomes become tangled?

Answer 24

when the bivalents condense and they supercoil close to each other

Question 25

What is genetic diversity?

Answer 25

the total number of different alleles in a population - the greater no. of different alleles, the greater genetic diversity

Question 26

Why will induvidual’s do better in environment changes with genetic diversity?

Answer 26

theres a wider range of alleles so a wide range of characteristics, so a greater probablitity that an induvidual will have a characteristic to suit the environment