Meiosis

Question 1

What is meiosis?

Answer 1

Meiosis is a form of nuclear division that results in the production of haploid cells from diploid cells

Question 2

What does meiosis produce?

Answer 2

1. Daughter cells that are genetically different from each other, introducing variation
2. Meiosis produces gametes in plants and animals, which are used in sexual reproduction

Question 3

Explain what meiosis involves:

Answer 3

Meiosis involves two nuclear divisions, which create four haploid daughter cells

Question 4

What is meant by a “haploid” cell?

Answer 4

“Haploid” means a cell that contains a single set of chromosomes

Question 5

Where are the haploid cells formed from?

Answer 5

Haploid cells are formed from a single diploid parent cell

Question 6

What are diploid cells?

Answer 6

Diploid cells contain the complete sets of chromosomes

Question 7

What two mechanism are used in meiosis to introduce variation?

Answer 7

Independent segregation of homologous chromosomes and crossing over between homologous chromosomes

Question 8

What part of meiosis involves the use the two mechanisms that introduce variation?

Answer 8

Both occur and are used during meiosis I (the first round of division)

Question 9

How many stages of meiosis are there? What are the stages of meiosis?

Answer 9

Interphase
Prophase
Metaphase
Anaphase
Telophase

Question 10

What are homologous pairs?

Answer 10

Homologous pairs are chromosomes that have the same genes, but different alleles

Question 11

When does independent segregation occur?

Answer 11

In meiosis I, when the homologous pair of chromsomes line up opposite each other in the middle of the cell.

Question 12

Explain independent segregation:

Answer 12

Maternal and paternal chromosomes will randomly go to either side of the equator when lining up in the middle of

Question 13

Draw an example diagram:

Answer 13

two paternal chromosomes on same side with two maternal chromosomes on the opposite side

one paternal chromosome and one maternal chromsome on the same side with other maternal and paternal chromosomes on opposite side

Question 14

What occurs after independent segregation?

Answer 14

These paternal and maternal chromosome pairs are the seperated, so one of each homologous pair ends up in the daughter cell

Question 15

What is an advantage of independent segregation?

Answer 15

Independent segregation can create a large number of possible combinations of chromosomes in the daughter cells produced

Question 16

How can the amount of possible combinations of chromosome be calculated? What does n stand for?

Answer 16

By using the calculation: 2 to the power of n (2^n

n = the number of homologous pairs

Question 17

What does

Question 18

How many combinations of chromosomes are possible for humans?

Answer 18

We have 23 chromosomes as humans.
So 2 to the power of 23.
Answer = 8,388,608 combinations

Question 19

When does crossing over occur?

Answer 19

Crossing over occurs when homologous pairs line up opposite each other at the equator in meiosis I

Question 20

What causes crossing over?

Answer 20

When homologous pairs are lined up opposite eachother at the equator in meiosis I, parts of the chromatids can become twisted around each other

Question 21

What occurs during crossing over?

Answer 21

Parts of chromatids become twisted around each other. This places tension on the chromatids, causing parts of the chromatid to break.

Question 22

What happens to the broken parts of the chromatids after crossing over?

Answer 22

The broken parts of the chromatids recombine with another chromatid, resulting in new combinations of alleles

Question 23

What are the difference between meiosis and mitosis?

Answer 23

1. Meiosis has two nuclear divisions, whereas mitosis has one nuclear division
2. Meiosis forms haploid cells but mitosis forms diploid cells
3. Meiosis introduce genetic variation compared to mitosis that creates genetically identical cells

Question 24

How can you identify meiosis in a life cycle?

Answer 24

You can identify meiosis as it involves a diploid (2 to the power of n) parent cell dividing to become a haploid cell

Question 25

What is random fertilisation?

Answer 25

Random fertilisation means during sexual reproduction the male and female gamete that fuse to produce an offspring are randomly selected from the pool of male and female gametes

Question 26

When considering random fertilisation, how many possible combinations of chromosomes are there?

Answer 26

There are actually (2^n)^2 possible combinations of chromosomes

Question 27

Considering there are (2^n)^2 possible combinations of chromosomes, how many combinations do humans have?

Answer 27

There are (2^23)^2 = 7.04 x 10^13

Question 28

Why do you not get genetically identical humans unless they are twins?

Answer 28

You do not get genetically identical humans unless they twins because there are 7.04 x 10^13 possible combinations of chromosomes allowing a lot of variation