Mitosis and Meiosis

Question 1

What is mitosis, what does it give rise to?

Answer 1

Part of the cell cycle when replicated chromosomes are separated into two new nuclei.

Gives rise to two new genetically identical cells.

Question 2

What are the 4 stages of mitosis?

Answer 2

Prophase
Metaphase
Anaphase
Telophase

Question 3

What happens in prophase?

Answer 3

Cell prepares to divide by tightly condensing its chromosomes and initiating mitotic spindle formation.

Phosphorylation of nuclear lamins causes the nuclear envelope to disintegrate.

Question 4

What happens in metaphase?

Answer 4

Chromosomes to align along the cell equator.

Question 5

What happens in anaphase?

Answer 5

Cohesins that bind sister chromatids together are cleaved, forming two identical daughter chromosomes.

Newly formed daughter chromosomes pulled to opposite ends of the cell.

Cell elongates.

Question 6

What happens in telophase?

Answer 6

Cell elongates even more.

If the nuclear envelope has broken down, a new nuclear envelope forms

The nucleolus reappears.

Both sets of chromosomes, begin to decondense.

Mitosis is complete.

Question 7

How does the mitotic spindle form in prophase?

Answer 7

Motor proteins push the centrosomes to poles.

Kinetochore microtubules begin to attach to chromosomal kinetochores.

Polar microtubules find and interact with corresponding polar microtubules from the opposite centrosome to form the mitotic spindle.

Question 8

How does metaphase arise (MT)?

Answer 8

Microtubules have attached to the kinetochores

Two centrosomes begin pulling the chromosomes towards opposite ends of the cell.

The resulting tension causes the alignment

Question 9

How do new nuclear membranes form in telophase?

Answer 9

Using the membrane vesicles of the parent cell’s old nuclear envelope.

Question 10

What is a kinetochore?

Answer 10

Microtubule-binding structure on the centromere.

Question 11

What causes sister chromatids to be pulled apart in anaphase?

Answer 11

Shortening of the kinetochore microtubules pulls the newly formed daughter chromosomes to opposite ends of the cell.

Question 12

What is meiosis, what does it produce?

Answer 12

Cell division that reduces the chromosome number by half

Creates four haploid cells, genetically distinct from the parent cell that gave rise to them

Question 13

What does meiosis produce in humans?

Answer 13

Haploid gametes

Question 14

Why is meiosis essential for gamete production (i.e why not mitosis)?

Answer 14

Haploid so zygote is diploid

Essential for sexual reproduction as it allows variation in gametes so that offspring can have varied alleles.

Question 15

What are the three key steps of a meiotic division?

Answer 15

DNA replication

Two rounds of division (meiosis I and II)

Question 16

What does meiosis I do?

Answer 16

Segregates homologous chromosomes

Question 17

Which meiosis step produces haploid from diploid?

Answer 17

Meiosis I

Question 18

What introduces variation into meiosis I?

Answer 18

Segregation of homologous chromosomes into daughter cells is random (independent segregation) therefore inducing variation. Some alleles from maternal chromosomes and some from paternal.

Crossing over/ exchange of information between non-sister chomatids

Question 19

When does crossing over occur?

Answer 19

Prophase I

Question 20

How does crossing over occur?

Answer 20

Non-sister chromatids of homologous chromosomes may exchange genetic information over regions of shared genes (but different alleles). At the sites where exchange happens, chiasmata form.

Question 21

When does independent segregation occur?

Answer 21

Anaphase I

Question 22

What is meiosis II?

Answer 22

Second meiotic division, involves separation of sister chromatids.

Question 23

What does meiosis II produce?

Answer 23

Four haploid (n) cells (not replicated

Question 24

What are the phases of the cell cycle?

Answer 24

Interphase (G1, S, G2)

Mitosis (M)

Question 25

What does meiosis I follow?

Answer 25

Normal S phase