NCERT Class 11-Biology: Chapter –10 Cell Cycle and Cell Division Part 3

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Question 11:

At what stage of cell cycle does DNA synthesis take place?

Answer:

S-phase of cell cycle .

Question 12:

It is said that the one cycle of cell division in human cells (eukaryotic cells) takes 24 hours. Which phase of the cycle, do you think occupies the maximum part of cell cycle?

Answer:

Interphase takes 23 hours out of 24 hours.

Question 13:

It is observed that heart cells do not exhibit cell division. Such cells do not divide further and exit ___________ phase to enter an inactive stage called ___________ of cell cycle. Fill in the blanks.

Answer:

Question 14:

In which phase of meiosis are the following formed? Choose the answers from hint points given below.

a. Synaptonemal complex ____________________________

b. Recombination nodules ____________________________

c. Appearance/activation of ____________________________

enzyme recombinase

d. Termination of chiasmata ____________________________

e. Interkinesis ____________________________

f. Formation of dyad of cells ____________________________

Hints : 1) Zygotene, 2) Pachytene, 3) Pachytene, 4) Diakinesis, 5) After Telophase-I /before Meosis-II, 6) Telophase-I /After Meiosis-I.

Answer:

a. Zygotene

b. Zygotene

c. Pachytene

d. Diakinesis

e. After telophase I/before meiosis

f. After Telophase I/after meiosis I

Short Answer Type Questions

Question 1:

State the role of centrioles other than spindle formation.

Answer:

Centriole forms microtubule and forms basal body of flagella.

Question 2:

Mitochondria and plastids have their own DNA (genetic material). What is known about their fate during nuclear division like mitosis?

Answer:

DNA present in mitochondria in plastids are called the extra chromosomal DNA.

They are independent of the nuclear division of the nuclear DNA. Hence, no effect of mitosis is seen on extra chromosomal DNA.

Question 3:

Label the diagram and also determine the stage at which this structure is visible.

Chapter 10 - Question 3 Image of this Structure is Visible

Chapter 10 - Question 3 Image of this Structure is Visible

Chapter 10 - Question 3 Image of this Structure is Visible

Answer:

Mataphase Stage

Mataphase Stage

Mataphase Stage

It indicates the early Metaphase stage.

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