6.2 Mitosis & Meiosis

Question 1

What are the stages of mitosis?

Answer 1

(I) PMAT+C

Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

Question 2

What is interphase

Answer 2

all the chromosomes are replicated to form one chromosome but 2 CHROMATIDS

1 centromere = 1 chromosome

Question 3

What is prophase

Answer 3

1. chromatin fibres begin to coil/condense to form chromosomes; nuclear membrane begins to break down.
2. protein microtubules form spindle structures linking each pole of the cell
3. (in animal cells/some plant cells) 2 centrioles move to either end of the cell to help spindles form and join
4. nuclear envelope has completely disappeared

Question 4

What is metaphase

Answer 4

1. chromosomes are moved to the middle of the cell by the spindle fibres, forming the metaphase plate and are held in position

Question 5

What is anaphase

Answer 5

1. the centromeres holding the chromatids together in ever chromosome divide
2. chromatids are pulled to either end of the cell by shortening spindle fibres

Question 6

What is telophase

Answer 6

1. a nuclear envelope starts to form around each group of chromosomes (singular chromatids each with a centromere) at either end of the cell
2. chromosomes start to uncoil and nucleolus is formed

Question 7

What is cytokinesis

Answer 7

IN ANIMAL CELLS

1. a cleavage furrow forms around the middle of the cell
2. cell surface membrane is pulled inwards by the cytoskeleton until each side is close enough to fuse together, forming 2 daughter cells.

IN PLANT CELLS

1. they have cell walls so it’s harder
2. vesicles from the Golgi apparatus begin to assemble in the same place as the metaphase plate
3. vesicles fuse together and the cell surface membrane, forming 2 daughter cells

Question 8

What is a diploid cell

Answer 8

a cell with 46 chromosomes

Question 9

what is a haploid cell

Answer 9

a cell with 23 chromosomes (a gamete)

Question 10

why is meiosis known as a reduction process

Answer 10

because in meiosis, the cells divide twice to form haploid daughter cells

Question 11

what are homologous chromosomes

Answer 11

when each nucleus contains matching sets of chromosomes; each chromosome in a homologous pair has the same gene at the same point on a chromatid/chromosome

Question 12

what are alleles

Answer 12

different versions of the same gene

Question 13

what are the stages of meiosis

Answer 13

1. meiosis I

2. meiosis II

Question 14

what happens in meiosis I

Answer 14

first division of cells when the homologous pair of chromosomes divide into 2 identical daughter cells with 23 chromosomes

1. prophase I -

Question 15

what happens in meiosis II

Answer 15

1. second division of cells, similar to mitosis, ending with new daughter cells; pairs of chromatids separate in each daughter cell, forming 2 more cells.

4 haploid cells are produced in total