16. Cell Division

Question 1

In cell cycle which phase accounts for 90-95% of time?

Answer 1

Interphase

Question 2

In eukaryotic cells the amount of DNA in a cell doubles during the

Answer 2

S phase

Question 3

What is the number of chromosomes in human cells formed by mitotic cell division and meiotic cell division respectively?

Answer 3

46,23

Question 4

Indicate number of chromosomes in a human egg and sperm cell

Answer 4

23 and 23

Question 5

Meiotic division is process leading to formation of specific cells in animals. What are these cells called???

Answer 5

Sex cells or gametes

Question 6

After DNA replication and before anaphase of mitosis, a chromosome has

Answer 6

two chromatids which have identical copies of DNA.

Question 7

Meiosis and mitosis have a number of features common. However only meiosis has the following feature:

Answer 7

The pairing up of homologous chromosomes

Question 8

Meiosis produces four cells that are

Answer 8

Haploid and are genetically different from each other

Question 9

Meiosis

Answer 9

Produces new combinations of genes

Question 10

Chromatids of homologous chromosomes ( crossing over) may exchange genetic material

Answer 10

during Prophase 1 meiosis

Question 11

At the end of telophase II of meiosis each of the four resulting cell contains

Answer 11

one full set of chromosomes, each a single chromatid.

Question 12

In animal cells cytokinesis

Answer 12

Starts at poles and pinches inwards

Question 13

Two copies of each chromosome are called??

Answer 13

Homologous chromosomes

Question 14

Meaning of haploid and diploid

Answer 14

Haploid: 1 father set, 1 mother set

Diplom: 1 set of chromosomes

Question 15

MITOSIS (3)

Answer 15

1. Purpose: growth and repair
2. Occurrence: ALL BODY CELLS
3. 1 division, produce 2N daughter cells

Question 16

MEIOSIS (3)

Answer 16

1. Purpose: gamete production
2. Occurrence: ALL SEX ORGAANSSS
3. 2 divisions produce 1N daughter cells

Question 17

Give 3 examples of activities in interphase

Answer 17

Interphase = metabolic activity to pro for next division

1. Copy of DNA
2. Protein and organelle synthesis

Question 18

Identify 5 stages in MITOTIC CELL DIVISION with support

Answer 18

1. INTERPHASE: chromosomes invisible
2. PROPHASE: chromosomes visible
3. METAPHASE: chromosomes line up MIDDLE
4. ANAPHASE: sister chromatids of each chromosome pulled apart TOWARD OPP POLE via contracting SF
5. TELEPHASE: new cell wall formed on new cells that teared apart.

Question 19

Describe how sister chromatids move via SF in cell

Answer 19

1. Centresome= control microtubles
2. Microtubles: contracts
3. Chromosome moves towards Centresome

Question 20

Describe what happens when cell cycle gets uncontrolled

Answer 20

Mechanisms regulate how often and how many times diff cells in body divide. If mechanism breakdown.

Cells divide uncontrollably-> tumour -> cAncers

Question 21

In cell cycle what are checkpoints??

Answer 21

Where cell cycle stops until ahead signal RECIEVED

Important checkpoints:
G1, g2 ,M

Question 22

Know sequence and order of MEIOSIS!!! (8 steps)!!!!!!

Answer 22

1. PROPHASE 1: Chromosome visible
2. METAPHASE 1: SF form(HORIZONTAL, HOMOLOGOUS CHROMOSOMES, move to middle cell, attached to SF by centromere)
3. ANAPHASE 1: SF contract. HOMOCHROM pulls APART (vertical position)
4. TELEPHASE 1: nuclear membrane around chromosomes
5. PROPHASE 2: nuclear membrane break down
6. METAPHASE 2: SP (VERTICAL) and chromosomes line up MIDDLE, attach to SF VIA centromere ( horizontal position)
7. ANAPHASE 2: sister chrimatids PULL apart as SF CONTRACTS
8. TELEPHASE 2:

1-nuclear membrane around each set chromosomes

2—-> after cytoplasmic division: 4 haploid daughter cells formed EACH WITH ONE MEMBER OF EACH HOMO PAIR

3- chromosome uncoil to chromatin again

Question 23

Explain how MEIOTIC cell division gives rise to genetic variation in offspring

Answer 23

Genetic variations= pairing up of HOMO CHROMOSOMES at prophase 1

Question 24

Where would transcription happen… PHASE????

Answer 24

In INTERPHASE (Z)

Z: transcription–> mRNA —> protein
protein synthesis occurs in interphase