1. meiosis and genetic variations

Question 1

haploid number of chromosomes

Answer 1

only one copy of each chromosome (this is what gametes have) (23)

Question 2

diploid number of chromosomes

Answer 2

2 copies of each chromosome (normal body cells) (46)

Question 3

genetic diversity

Answer 3

1. fertilisation is random
2. crossing over in meiosis 1 (homologus pairs swap bits of chromatids, exchanging alleles)
3. independent segregation

Question 4

meiosis

start

Answer 4

1. DNA unravels and replicates so 2 copies of each chromosome (chromatids)
2. DNA condenses to form chromosomes each made from 2 sister chromatids which are joined by centromere

Question 5

meiosis 1

Answer 5

chromosomes arrange themselves into homogulous pairs

homologous pairs then separate halving chromosome number

Question 6

meiosis 2

Answer 6

pairs of sister chromatids that make up each chromosome are separate (centromere divided)
4 haploid cells genetically different from eachother produced

Question 7

independent segregation

Answer 7

homologous pair of chromosomes separated during meiosis 1 random which chromosome from each pair ends up in which daughter cell
4 daughter cells have different combinations of maternal and paternal chromosomes

Question 8

mitosis vs meiosis

Answer 8

mitosis
1. cells with same number of chromosomes as parent cell
2. daughter cells genetically identical to each other and to parent cell
3. produces 2 daughter cells
meiosis
1. cells with half number of chromosomes as parent cell
2. daughter cells genetically different
3. produces 4 daughter cells

Question 9

crossing over

Answer 9

meiosis 1
chromatids of homologus pairs cross over / twist around eachother bits of chromatids break off and swap (as in the paternal crosses with maternal)
= different combo of alleles

Question 10

chromosome mutations

Answer 10

1. non-disjunction
   failure of chromosomes to separate properly
2. extra copy of chromosome 21 - down syndrome
3. when gamete fuses with another gamete - 3 copies of chromosome 21