Chapter 2 - Meiosis

Question 1

What is sexual reproduction?

Answer 1

Combines genetic material from 2 parents to form a gentically unique individual

Question 2

What is one advantage of sexual reproduction

Answer 2

Increases genetic diversity
Increases survival chances

Question 3

What are the two disadvantages of sexual reproduction?

Answer 3

Takes time and energy to find a mate
Lower rate of offspring production

Question 4

What are body cells/somatic cells called?

Answer 4

Diploid cells (2n)

Question 5

What are haploid cells?

Answer 5

Haploid cells are our gametes/sex cells and only contain one copy of a chromosome (n)

Question 6

What is the total number of chromosome is one somatic cell?

Answer 6

46
(22 pairs of autosomes - non sex chromosome)
(1 pair of sex chromosomes)

Question 7

What is a homolog/homologous pair?

Answer 7

A pair of chromosomes which contain the genetic code for the same features

Question 8

What is Meiosis?

Answer 8

Producing four haploid gametes from a single parent cell

Question 9

Where does Meiosis occur?

Answer 9

Gonads

Question 10

What differentiates Meiosis from Mitosis?

Answer 10

Meiosis has two deparate division events rather than one because they are producing four haploid gametes.

Question 11

What happens before meiosis begins?

Answer 11

DNA replication occurs during the S phase to produce identical sister chromatids

Question 12

What does Meiosis 1 involve?

Answer 12

Separation of homologous chromosome from 2n to n

Question 13

How many stages are there in total for Meiosis?

Answer 13

8 (Meiosis stage 1 = 4 phases. Meiosis stage 2 = 4 phases)

Question 14

What is a parent cell called?

Answer 14

Germline cell - diploid (2n)

Question 15

Describe the events at prophase 1

Answer 15

• replicated DNA condenses
• centrioles start to produce spindle fibres
• Nuclear envelope breaks down
• Spindle fibres attach at centromeres and move to opposite ends

Question 16

What occurs at prophase 1?

Answer 16

Synapsis

Question 17

What is synapsis?

Answer 17

The homologous chromosome will pair up

Question 18

What is crossing over?

Answer 18

The sister chromatids closest to each other cross over
Two chromatids can swap equivalent genetic material

Question 19

What is a Chiasma?

Answer 19

The point at which crossing over occurs

Question 20

Describe the events at Metaphase 1

Answer 20

Chromosomes line up in homologous pair at centre

Question 21

Describe the events at Anaphase 1

Answer 21

Spindle fibres are pulled back
Homologous pair are separated
Sister chromatid remains together

Question 22

Describe the events at Telophase 1 and cytokineses

Answer 22

Often occur at the same time
Cleavage furrow or cell plate forms and separates the cytoplasm into two separate cells

Question 23

What does Meiosis 2 involve?

Answer 23

Separates sister chromatids

Question 24

Which stage of Meiosis is similar to Mitosis?

Answer 24

Meiosis stage 2

Question 25

Describe the events at prophase 2

Answer 25

Spindle reforms and attaches to centromeres of condensed chromosomes

Question 26

Describe the events at metaphase 2

Answer 26

Chromosomes line up down the equator of the cell

Question 27

Describe the events at anaphase 2

Answer 27

Spindle fibres pull back towards centrioles
Sister chromatids are separated

Question 28

Describe the events at telophase 2 and cytokineses

Answer 28

• Groups of chromosomes reach the poles of the cell
• Nuclear envelope starts to form around the group of chromosomes
• Spindle fibres break down and chromosomes start to unwind
• Cleavage furrow forms

Question 29

How does meiosis produce genetically different offspring? (3 ways)

Answer 29

• The chromosomes are arranged randomly
• Process of crossing over
• Random fertilisation of haploid gametes

Question 29

What is the product of Meiosis 2?

Answer 29

Four non-identical haploid gametes