Meiosis and genetic variation
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1
What are gametes?
Sperm and egg cells.
2
How many chromosomes do gametes have?
23 chromosomes.
3
What happens during fertilisation?
Gametes fuse to form a zygote.
4
What does the zygote develop into?
An embryo.
5
What ensures genetic diversity during fertilisation?
Random fertilisation.
6
What type of cell division forms gametes?
Meiosis.
7
Where does meiosis occur?
Reproductive organs.
8
What does meiosis halve in gametes?
Chromosome number.
9
How many divisions occur in meiosis?
Two divisions.
10
What happens before meiosis starts?
DNA replicates.
11
What does each chromosome consist of after replication?
Two chromatids.
12
What happens in meiosis I?
Homologous chromosomes are separated.
13
What happens in meiosis II?
Sister chromatids are separated.
14
What cells are produced by meiosis?
Four haploid cells.
15
What are homologous chromosomes?
Pairs of chromosomes with the same genes.
16
What happens in crossing over?
Chromatids swap genetic material.
17
What does crossing over increase?
Genetic variation.
18
What happens in independent segregation?
Chromosomes randomly separate.
19
How many chromosomes do daughter cells have after meiosis?
23 chromosomes.
20
What type of variation does meiosis cause?
Genetic variation.
21
What is the chromosome mutation called when chromosomes fail to separate?
Non-disjunction.
22
What condition is caused by an extra chromosome 21?
Down's syndrome.
23
How does non-disjunction occur?
Chromosomes fail to separate in meiosis.
24
What does a zygote with an extra chromosome have?
Three copies of chromosome 21.
25
What does haploid mean?
One set of chromosomes.
26
What does diploid mean?
Two sets of chromosomes.
27
What are the differences between mitosis and meiosis?
Mitosis produces identical cells, meiosis does not.
28
How many daughter cells are produced in mitosis?
Two daughter cells.
29
How many daughter cells are produced in meiosis?
Four daughter cells.
30
What are chromatids?
Strands of a replicated chromosome.
31
What process ensures no two gametes are identical?
Independent segregation.
32
What process results in genetic diversity in offspring?
Crossing over and random fertilisation.
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