Meiosis

Question 1

What are gametes?

Answer 1

They are the sperm cells in males and egg cells in females

Question 2

Hows a diploid zygote formed?

Answer 2

In sexual reproduction two haploid gametes join together ar fertilisation to from a diploid zygote, which divides and develops into a new organism

Question 3

Definition of homologous chromosomes

Answer 3

A pair of chromosome one from the mum and one from the dad that pair up with each other inside a cell during meiosis. They have the same size and genes although they could have different version of the genes called alleles

Question 4

Why do gametes have a haploid number of chromosomes?

Answer 4

As theres only one copy of each chromosome

Question 5

Why are cells formed by meiosis are all genetically different?

Answer 5

Because each new cell ends up with a different combination of chromosomes

Question 6

Definition of meiosis

Answer 6

Its a type of cell division that happens in the reproductive organs to produce gametes

Question 7

What does meiosis begins with?

Answer 7

Interphase - during interphase, the cell’s DNA unravels and replicates to produce double armed chromosomes called sister chromatids

Question 8

What is Meiosis 1

Answer 8

Its the reduction division (it halves the chromosome number) - it has 4 stages Prophase, Metaphase, Anaphase, Telophase

Question 9

What happens in Prophase 1

Answer 9

> The chromosome condense, getting shorter and fatter
Homologous chromosome pair up - 1 with 1, 2 with 2 etc…
Crossing-over occurs
Centrioles start moving to opposite ends of the cell, forming the spindle fibres
Nuclear envelope breaks down

Question 10

What happens in Metaphase 1

Answer 10

> The homologous pairs line up across the centre of the cell and attach to the spindle fibres by their centromeres

Question 11

What happens in Anaphase 1

Answer 11

> The spindles contract, pulling the pairs apart (One chromosome goes to each end of the cell)

Question 12

What happens in Telophase 1

Answer 12

> A nuclear envelope forms around each group of chromosomes

> Cytokinesis occurs and two haploid daughter cells are formed

Question 13

What happens in meiosis 2

Answer 13

The 2 daughter cells undergo Prophase 2, Metaphase 2, Anaphase 2, Telophase 2 and cytokinesis

Question 14

What is the difference between meiosis 1 and meiosis 2

Answer 14

In meiosis 2 half theres half the number of chromosomes

Question 15

What happens in Anaphase 2

Answer 15

The sister chromatids are separated- each new daughter cell inherits one chromatids from each chromosome. Four haploid daughter cells are produced.

Question 16

What leads to genetic variation

Answer 16

1. crossing over of chromatids

2. independent assortment of chromosomes

Question 17

Describe crossing over of chromatids

Answer 17

> During Prophase 1 of meiosis 1, homologous pair of chromosomes come together and pair up.
The chromatids twist around each other and bits of chromatids swap over.
The chromatids still contemn the same gene but now have a different combination of alleles

Question 18

how does crossing over of chromatids lead to genetic variation

Answer 18

Because each cell has different chromatid and therefore a different set of alleles, which increases genetic variation in potential offspring

Question 19

How does independent assortment of chromosomes lead to genetic variation?

Answer 19

The shuffling of chromosomes leads to genetic variation in any potential offspring