Mitosis and Meiosis

Question 1

G1 Phase

Answer 1

Organelles/ other cyt. comp. replicate/ form.
Cell incr in size

Question 2

S Phase

Answer 2

DNA duplicated and chromatids form within the nucleus
Histones produced

Question 3

G2 Phase

Answer 3

Spindle proteins synthesised.
Chr checked for error and repaired as nec
Second growth phase

Question 4

What does mitosis ensure regarding daughter cells?

Answer 4

Ensures daughter cells produced during cell division have exactly the same chr makeup as parent cell

Question 5

How does mitosis differ from cytokinesis?

Answer 5

Mitosis is div of chr
Cyt is div of cell into 2 daughter cells

Question 6

What does G1 check?

Answer 6

1: Cell reached crit size
2: Enough nutr avail for next stages to take place
3: Nec growth factors in place
4: No DNA damage

Question 7

If req are met what happens?
And if not??

Answer 7

yes: S phase- DNA synth takes place
no: G0 resting phase

Question 8

What does G2 check?

Answer 8

DNA rep (during S phase) has taken place acc and no DNA damage.
If all good mitosis happens

Question 9

What is cancer?

Answer 9

Uncontr cell div- mitosis out of control

Question 10

What does cancer inv in rel to mitosis?

Answer 10

Cannot enter G0- inv breakdown in ability to regulate checkpoints of cell to reg process of cell div

Question 11

How does Vincristine work?

Answer 11

Inhibits the formation of microtub- binds to tubulin in microtub and stops spindle fibres contracting and pulling chromatids apart- prev ANAPHASE

Question 12

How do antimetabolites i.e Fluouracil work?

Answer 12

S phase inhib- prev DNA synth i.e Fluouracil inhibits enzyme inv in making nucleotides that cont base thymine- prev DNA synth

Question 13

When is the support of histones particularly important?

Answer 13

When chromatin condenses to form visible chr during nuclear div

Question 14

How is a nucleosome formed?

Answer 14

Histone proteins folded into compact stacks and DNA coils tightly around stack to form this str

Question 15

What is diploidy?

Answer 15

Situation in which a cell has 2 sets of chr i.e a pair of each type

Question 16

What is haploidy?

Answer 16

Situation in which a cell has a single set of unpaired (non-homologous) chr

Question 17

Why are homologous chromosomes not id?
But what is similar about them?

Answer 17

Carry the same genes in same seq along l. as partner chr does.
Not identical as alleles for small no. genes may differ in 2 chr

Question 18

Prophase

Answer 18

Chromatin condenses to form chr
Centrioles in animal cells move towards opposite poles
Spindle begins to form
As each chr continues to condense, 2 chromatids joined at centromere become apparent
Nucleolus disappears
Nucl membr breaks down

Question 19

Metaphase

Answer 19

chr consisting of 2 chromatids align along equator and join at centromeres to spindle fibres

Question 20

Anaphase

Answer 20

Centromeres attaching 2 chromatids of each chr split
Contr of spindle fibres pull chr of sister chromatids apart
Sister chromatids move towards opposite ends

Question 21

Telophase

Answer 21

Cleavage furrow forms in animals
Each chromatid now a sep chr
2 groups of chr reach opposite poles of cell
A new nuclear env forms around each group
Chr decondense and bec more visible
Nucleolus reappears
Spindle dis as its broken down

Question 22

Describe difference between cytokinesis of animal and plant cells:

Answer 22

Animal: cleavage furrow forms as cell surf membr invaginates and eventually splits the cell in two
Plant: cell plate precursor to a new cell wall is laid down along the centre of the cell. GA plays imp role in syth mat needed in the form of the new wall

Question 23

How does meiosis differ from mitosis?

Answer 23

Only takes place in reprod organs
Inv 2 div resulting in 4 daughter cells
Chr arrangements in daughter cells are both different from each other and different from the parent cell

Question 24

Prophase I

Answer 24

As chr condense it becomes apparent that homologous chr have paired and lie alongside each other- each pair is known as a bivalent
Chromatids appears- chr in a bivalent are entwined at points called chiasmata
Chromatids may break @ chiasmata and rejoin with dif chromatids resulting in crossing over or recombination

Question 25

Metaphase I

Answer 25

Bivalents move to equator of the spindle
Each chr of pair becomes attached to a spindle fibre by its centromere

Question 25

Anaphase I

Answer 25

Pulling by the spindle fibres causes the homologous chr to move apart towards opp poles
Homologous chr are sep- each chr still consists of 2 chromatids

Question 26

Telophase I

Answer 26

Chr reach opp poles of cell
Nucl membr forms around each sep group of chr, each nucleus cont haploid no chr

Question 27

What is meiosis ii similar to in its processes only with 2 more daughter cells prod?

Answer 27

Mitosis

Question 28

What is IA?

Answer 28

Independent assortment/random alignment of homologous chromosomes;
resulting in new chromosome combinations in gametes;

Question 29

What is CO?

Answer 29

exchange of genetic information/recombination of genes between two
chromatids/non sister chromatids/homologous chromosomes/new allelic
combination;

Question 31

Describe independent assortment

Answer 31

One chromosome from each hom pair can enter a gamete
For any one gamete it can be either of 2 homologous chr from any particular pair
The way one chromosome pair lines up is totally independent of how any other pair aligns

Question 32

Crossing Over

Answer 32

2 chr of homologous pair align themselves side by side as interphase progresses As each chromatids separate into 2 chromatids following Dna replication resulting bivalent consists of 4 chromatids lying side by side
Sometimes 2 non- sister chromatids (from different chromosomes in homologous pair) break and exchange sections with each other

Question 33

Why is crossing over significant?

Answer 33

Exchanges sections of genes between chromatids from 2 chr in a homologous pair- this can work bc genes will be same