Mitosis and Meiosis

Question 1

What are the 2 phases of the cell cycle?

Answer 1

interphase and mitosis

Question 2

What are the subphases of interphase?

Answer 2

1. G1 2.S 3.G2

Question 3

What is G0?

Answer 3

resting phase - no cell division takes place

Question 4

Explain what happens in G1?

Answer 4

cell undergoes growth of cellular constituents and performs normal cell functions

Question 5

Explain what happens in S?

Answer 5

DNA is replicated

Question 6

Explain what happens in G2?

Answer 6

cell undergoes further growth and prepares for mitosis

Question 7

What is mitosis?

Answer 7

mitosis is the division of the nucleus and cytoplasm that results in formation of 2 daughter cells with identical DNA to the parent cell

Question 8

What is karyokinesis?

Answer 8

attachment of microtubules to the centromeres of chromosomes

Question 9

What is cytokinesis?

Answer 9

seperation of cytoplasm of a parental cell to form two cells

Question 10

What are the subphases of mitosis?

Answer 10

1. prophase 2. metaphase 3. anaphase 4. telophase

Question 11

Explain what happens in Prophase?

Answer 11

nuclear envelope and nucleoplasm dissolves

Question 12

Explain what happens in Metaphase?

Answer 12

chromasomes are lined along the metaphase plate

Question 13

What are the subphases of Metaphase?

Answer 13

1. prometaphase - nuclear membrane disintegrates 2. metaphase - chromosomes line up along the metaphase plate

Question 14

Explain what happens in Anaphase?

Answer 14

sister chromatids are pulled apart by tubules of the mitotic spindle

Question 15

Explain what happens in Telophase?

Answer 15

nuclear membrane and nucleoplasm forms around chromatids and the cell pinches inwards seperating the cell into two

Question 16

What is the contractile ring?

Answer 16

a ring shaped structure located just beneath the plasma membrane at the future division site, is assembled in anaphase and contracts as cells divide

Question 17

What is the contractile ring made of?

Answer 17

composed of actin and myosin

Question 18

What are centrososmes?

Answer 18

where micrtotubules come from - centrioles are in centrosomes

Question 19

What are centrioles?

Answer 19

cylindrical organelle made mainly of the protein tublin - a bound pair of centrioles are in a centrosome

Question 20

Where does the mitotic spindle attach?

Answer 20

centromere

Question 21

What is meiosis?

Answer 21

one parent cell (2n) divides to produce four haploid daughter cells which are then processed into gametes - sexual reproduction

Question 22

What are the stages of meiosis?

Answer 22

meiosis I and meiosis II

Question 23

What are the phases of Meiosis I?

Answer 23

1. prophase I 2. metaphaseI 3. anaphase I 4. telophase I

Question 24

Explain what happens in Prophase I?

Answer 24

1. nuclear membrane disintegrates 2. chromosomes find their homologues 3. synapsis and crossing over takes place

Question 25

What is synapsis and crossing over?

Answer 25

non-sister chromatids line up side-by-side & exchange genetic information between them

Question 26

Importance of synapsis and crossing over?

Answer 26

allows new combination of genetic material which will become part of a new offspring - introduces variation and therefore evolution/adaptation to changing environments

Question 27

Explain what happens in Metaphase I?

Answer 27

1. replicated chromosomes line up side by side according to their homologous characterstics along the metaphase plate 2. independent assortment takes place

Question 28

What is independent assortment?

Answer 28

replicated chromosomes line up side by side according to their homologous characteristics but the arrangement is random and can be different

Question 29

Explain what happens in Anaphase I?

Answer 29

homologous chromosomes are sepereated from each other by microtubules

Question 30

Explain what happens in Telophase I?

Answer 30

nuclear membrane reforms around the chromosomes and the cell splits into 2 daughter cells via cytokinesis

Question 31

What are the phases of Meiosis II?

Answer 31

1. prophase II 2. metaphase II 3. anaphase II 4. telophase II

Question 32

Explain what happens in Prophase II?

Answer 32

nuclear membrane disintegrates

Question 33

Explain what happens in Metaphase II?

Answer 33

chromosomes line up along metaphase plate

Question 34

Explain what happens in Anaphase II?

Answer 34

mitotic spinfle seperates the chromatids

Question 35

Explain what happens in Telophase II?

Answer 35

nuclear membrane reforms around chromatids

Question 36

Event after telophase?

Answer 36

cytokinesis - the cell splits into 2

Question 37

Differences between Meiosis and Mitosis?

Answer 37

1. metaphase - in meiosis homologoues chromosomes line up next to each other and in mitosis chromosomes line up on top of one another 2. meiosis has 2 stages and produces 4 haploid daughter cells whereas mitosis has 1 stage and produces diploid daughter cells 3. in meiosis the daughter cells are not genetically identical to the parent cell where as in mitosis the daughter cells are genetically identical to the parent cell

Question 38

Why is meiosis necessary?

Answer 38

for genetic variation in offspring

Question 39

What is Downs Syndrome?

Answer 39

3 copies of the chromosome 21 and not 2

Question 40

What is Klinefelters Syndrome?

Answer 40

2 X chromosomes and 1 Y chromosome - they exhibit the male phenotype but fail to dvelop secondary sexual characteristics + almost always sterile

Question 41

What is Turners Syndrome?

Answer 41

individuals are female but have only 1 X chromosome