XI: Chapter 10- Cell cycle and cell division

Question 1

In the 24 hours duration of human cell cycle how long does cell division proper last?

Answer 1

One hour

Question 2

In which phase do the centrioles duplicate?

Answer 2

S phase

Question 3

What occurs in G2 phase?

Answer 3

Protein synthesis

Question 4

Which is the most dramatic period of cell cycle?

Answer 4

M phase

Question 5

When do centrioles move towards the opposite poles?

Answer 5

In prophase

Question 6

Asters are made of

Answer 6

Microtubules

Question 7

What forms the mitotic apparatus?

Answer 7

Asters along with the mitotic spindle

Question 8

In which phase of cell cycle is morphology of chromosomes best studied?

Answer 8

Metaphase

Question 9

What serves as site for attachment of spindle fibres?

Answer 9

Kinetochores

Question 10

Where does the wall formation start during cytokinesis in cell?

Answer 10

From the centre towards the periphery

Question 11

What is the precursor of cell wall?

Answer 11

Cell plate

Question 12

Cell plate represents

Answer 12

Middle lamella

Question 13

Synapse formation in meiosis occurs in which phase?

Answer 13

Zygotene of meiosis I

Question 14

Bivalents are formed in which stage of meoisis?

Answer 14

Zygotene of meoisis I

Question 15

Bivalents are visible clearly in which phase of meiosis?

Answer 15

Pachytene of meiosis I

Question 16

What marks the beginning of diplotene?

Answer 16

Dissolution of synaptonemal complex

Question 17

Chiasmata formation occurs in which phase of meiosis?

Answer 17

Diplotene

Question 18

When is a dyad of cells formed in meoisis?

Answer 18

Telophase I

Question 19

Who discovered amitosis?

Answer 19

Flemming

Question 20

What happens to nuclear membrane during amitosis?

Answer 20

It remains intact

Question 21

In which phase does atp synthesis occur in mitosis?

Answer 21

G1

Question 22

When does histone doubling occur in cell cycle?

Answer 22

S-phase

Question 23

When does tubulin synthesis occur?

Answer 23

G2

Question 24

How many check points are present in cell cycle?

Answer 24

Three- G1 checkpoint, G2 checkpoint, Metaphase-anaphase checkpoint

Question 25

When is CDK (Cyclin-dependent kinase) activated?

Answer 25

G1 checkpoint

Question 26

What are chalones?

Answer 26

Tissue specific suppressant, inhibitor of cell cycle

Question 27

What are the three types of spindle fibres?

Answer 27

Continuous/interpolar fibre (from one pole to another)
Internodal (between two centromere)
Tractile (between pole and centromere)

Question 28

Which is the best material to study meiosis?

Answer 28

Pollen mother cell

Question 29

What change occurs in number of chromosomes at the end of meiosis I ?

Answer 29

Chromosome number reduces to half

Question 30

What change occurs in dna content at the end of meiosis I ?

Answer 30

DNA content remains the same as parent

Question 31

At the end of meiosis II what happens to dna and chromosomal content?

Answer 31

Dna content reduces to half and chromosome number remains same as meiosis I

Question 32

Following DNA replication in S-phase, the DNA content becomes 4c and a pair of sister chromatids are formed from each chromosome. What is the number of chromosomes? Why?

Answer 32

The number of chromosomes is 2n before and after DNA replication because a pair of sister chromatids is counted as one chromosome.

So even when DNA content doubles leading to the formation of sister chromatids in each chromosome, chromosome number remains the same.

Question 33

The chromosome number in a diploid cell (2n) remains the same (2n) even after replication of DNA in S-phase, then how do the two cells formed at the end of mitosis have 2n chromosomes each?

Answer 33

When DNA replicated each chromosome develops a pair of sister chromatids. The chromosome is still counted as a single chromosome (with a pair of sister chromatids). When the cell undergoes M phase, the sister chromatids separate and so each daughter cell has 2n ploidy.

Question 34

How many chromatids does diploid cell (2n) have?

Answer 34

2n

Question 35

How many chromatids does a diploid cell have after s-phase?

Answer 35

4n

Question 36

How many arms does y chromosome have?

Answer 36

1

Question 37

How many arms does x chromosome have?

Answer 37

2