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 - one chromosome from each pair

Question 8

What happens during meiosis 2?

Answer 8

Separation of sister chromatids
Produces 4 haploid daughter cells

Question 9

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

Answer 9

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

Question 10

What does it mean that meiosis is reduction division?

Answer 10

The no. Of chromosomes half

Question 11

How does meiosis increase genetic diversity?

Answer 11

Crossing over
Random fusion of gametes
Independent segregation

Question 12

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

Answer 12

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

Question 13

What is random fusion of gametes?

Answer 13

each gamate has a unique combination of alleles
male and female gamates fuse to form a zygote
produces new allele combinations in the zygote

Question 14

How does random fusion of gametes create genetic diversity?

Answer 14

results in new combinations of alleles

Question 15

What are recombinant chromosomes?

Answer 15

the new combination of alleles after crossing over are not the same as the parent chromosomes

Question 16

What is independant segregation?

Answer 16

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

Question 17

How do the chromosomes become tangled?

Answer 17

when the bivalents condense and they supercoil close to each other

Question 18

What is genetic diversity?

Answer 18

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

Question 19

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

Answer 19

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

Question 20

How can a gene mutation have no effect on an individual?

Answer 20

changes the amino acid but not the tertiary structure
the new allele produced is recessive
genetic code is degenerate

Question 21

How can a gene mutation have a positive effect for an individual?

Answer 21

results in change in polypeptide that positively changes the properties of the protein
may result in increased reproductive success or survival

Question 22

What is a mutagenic agent?

Answer 22

a factor that increases the rate of mutattions

Question 23

What is non-disjunction?

Answer 23

chromosome mutation - chromosomes fail to separate in meiosis

Question 24

How does random fusion of gemates increase genetic diversity?

Answer 24

produces new allele combinations

Question 25

What are the 2 ways that meiosis can lead to genetic variation?

Answer 25

crossing over and independent segregation

Question 26

What is the process of independent segregation?

Answer 26

1. homologous chromosomes align opposite at the equator, it is random which side the maternal and paternal chromomes align 2. these separate int daughter cells 3. produces a large number of possible combinations of chromomes in the daughter cells

Question 27

How does crossing over lead to genetic variation?

Answer 27

new combinations of alleles in the gametes

Question 28

What are the 3 ways genetic variation arises?

Answer 28

meiosis mutation random fusion of gametes

Question 29

Why are triploid offspring sterile?

Answer 29

have an extra set of chromosomes homologous chromosomes do not pair and do not separate no meiosis takes place

Question 30

What is a gene mutation?

Answer 30

change in the base sequence of DNA results in the formation of a new allele

Question 31

Describe the process of crossing over and how it increases genetic diversity

Answer 31

1. homologous pairs of chromosomes associate to form a bivalent 2. chiasma form 3. equal lengths of the non-sister chromatids are exhanged 4. producing new combinations of alleles

Question 32

Why would a mutation be present in all cells in the body?

Answer 32

mutation occurs in gamete all cells are derived from the zygote by mitosis