Multiple Choice Questions on Cell Cycle

Q1. Which of the following choice is incorrect in relation to the interphase stage?

a) Period of great metabolic activity
b) It covers over 95% of the total duration of cell cycle
c) Absence of replication of DNA
d) Also called as preparatory phase


Q2. Duplication of DNA occurs in:

a) G1 phase
b) S phase
c) G2 phase
d) M phase


Q3. If cell division is restricted in G1 phase of a cell cycle, the condition is known as:

a) G1 phase
b) G2 phase
c) G0 phase
d) M phase

Q4. Go-phase of cell denotes:

a) Check point before entering the next phase
b) Death of cell
c) Temporary pause
d) Exit of cell from cell cycle

Q5. The sequence of cell cycle is:

a) S, M, G1 and G2
b) G1, G2, S and M
c) S, M, G2 and G1
d) G1, S, G2 and M

Q6. The synthesis of spindle proteins occur during:

a) G1-phase
b) S-phase
c) G2-phase
d) M-phase


Q7. Histone protein synthesis occurs during:

a) G1 phase
b) G2 phase
c) M phase
d) S phase

Q8. During cell cycle, DNA replicates:

a) Once
b) Twice
c) Many times
d) Not at all

Q9. Which of the following doubles during S phase:

a) Mitochondria
b) Chloroplast
c) Golgi body
d) All of the above

Q10. Which of the following phase of a cell cycle is called invisible phase:

a) G1 phase
b) S phase
c) G2 phase
d) M phase


Q11. If the DNA content in a cell at G1 phase is 2C, what will be the DNA content at S phase?

a) 2C
b) 4C
c) 1C
d) None



Q12. If the DNA content of a cell at G1 phase is 2C what will be the DNA content of its daughter cells after mitotic division?

a) 2C
b) 4C
c) 1C
d) None

Q13. The DNA content of a cell at G1 phase is 2C, what will be the DNA content of its daughter cells after meiosis II?

a) 2C
b) 1C
c) 4C
d) All of the above











Answer Key:

1. c      4. d     7. d     10. b   13. b
2. b      5. b     8. a     11. b
3. c      6. c     9. d     12. a

Read More

How the Cell Cycle is Controlled?

Cell cycle is run by a group of special proteins, called Cyclins and Cdks (cyclin dependent kinases). A cell reproduces by performing an orderly set sequences of irreversible events in which it duplicates its contents and then divide into two. These events are collectively called as cell cycle.

Molecular biologists have made a remarkable progress in identifying the biomolecules that control the cell cycle. Scientists working on frog eggs and yeast cell concluded that the activity of enzymes such as cyclin dependent kinases (Cdk‘s) regulate the cell cycle.

Kinase is a type of enzyme that is responsible for removing a phosphate group from ATP and add to another protein. The kinases involved in the cell cycle are called Cdks because they are activated when they combine with the key protein, cyclin.

At some check-point in the cell cycle (G1 à S and G2 à M), a kinase enzyme combines with cyclin and this moves the cell cycle forward. G1 or S-kinase is capable of initiating the replication of DNA once it combines with S-cyclin. After some time, S-cyclin is destroyed and S-kinase is no longer active. M-kinase, on the other hand, is capable of turning on mitosis once it combines with M-cyclin.

G1 to S transition is carried out by G1 or S cyclin + cdc 2 kinase
G2 to M transition is triggered by maturation promoting factor (MPF) formed by mitotic cyclin + cdc 2 kinase

Read More

Measures of DNA Content and Chromosome Content

The amount of DNA within a cell change following each of the following events:

• Fertilization
• DNA synthesis
• Mitosis
• Meiosis

We use ‘C’ to represent DNA content in a cell and ‘N’ to represent the number of complete sets of chromosomes.

In a gamete -- the amount of DNA is say, 1C
And the number of chromosomes say,    1N

Upon fertilization, both the DNA content and the number of chromosomes doubles to 2C and 2N respectively.

Following DNA synthesis, the DNA content doubles again to 4C, but each pair of sister chromatids is still as a single chromosome, so the number of chromosomes remain unchanged at ‘2N’

Read More

What is the Difference Between Mitosis and Meiosis?

Read More

What is Cell Cycle? What are the Different Phases of a Cell Cycle?

Complete lifecycle of a cell is called the cell cycle. In other words, it is an orderly series of changes that occurs in a cell by which the cell duplicates its genetic material along with that it duplicates other content; finally, it divides and results in the formation of two daughter cells. An interphase occurs between two phases. During interphase, a cell grows in size and prepares itself for the next division. Interphase is also the most active phase of a cell cycle. During this phase, the metabolism activity of cell increases and a series of changes occur during the same phase. However, these changes are not visible under the microscope. That is why some scientists have termed interphase as a Resting Phase. Howard and Pelc -- two scientists have classified interphase into three sub-stages:




 The time taken by the cell to divide is known as generation time. For yeast, generation time is about 90 minutes.

(I) G1 Phase / Pre-DNA synthesis phase / Post-mitotic phase:
-- Maximum growth of the cell along with an increase in the size of the nucleus is seen.
--  It is the longest duration of the Interphase
-- During this phase, there is synthesis of nucleotides / amino acids / energy-rich molecules (ATP)
-- Polymerisation of nucleotide results in RNA synthesis.
-- RNA polymerase becomes active along with the enzymes for DNA synthesis.an
-- Synthesis of amino acids, which are involved in histone protein synthesis.

(II) S-Phase (DNA Synthesis Phase):

-- DNA duplication / replication takes place.
-- Chromosome consists of two chromatids
-- Centriole duplication occurs in the cytoplasm
-- Amino acids polymerize and form histone proteins
-- Assembly of kinetochore subunits
-- The duplicated chromosomes will not appear during this phase and that's why this phase is known as INVISIBLE PHASE


G2-Phase / Post-DNA synthesis phase / Pre-mitosis phase

-- Known as the second growth phase.
-- Cell size increases
-- Nucleus size increase
-- RNA synthesis takes place
-- Protein synthesis takes place
-- Duplication of most of the cell organelles (along with the division of mitochondria and division of plastids)
-- Biochemicals are formed for the synthesis of spindle fibres.
-- Tubulin protein synthesis takes place.
-- It is also signified by the synthesis of some protein kinases for the regulation of cell division

Read More