Cell Cycle And Division

Question 1

What is cell division ?

Answer 1

Cell division is the process in which a cell(parent cell) is divided to form a new cell (daughter cell )

Question 2

How does the individual chromosome changed when the cell is dividing ?

Answer 2

• when the cell is not dividing, individual chromosomes in the cell are not visible. It is because they exist as a mass of long and thin fibres called chromatin.
• when the cell is dividing, the chromosome in the cell appear shorter and thicker as the chromatin fibre coil up tightly. The chromosome became visible.

Question 3

What is chromosome ?

Answer 3

• Chromosome are structures made up of DNA and proteins
• when the cell is not dividing, chromosome exist as chromatin.
• when cell division begins, each chromosome consists of two identical sister chromatids joined at centromere.

Question 4

What are diploid cells and haploid cells?

Answer 4

Diploid cells are cells that contain two sets of chromosomes while haploid cells are those that contain only one set.

Question 5

How does the number of chromosomes vary within and among species?

Answer 5

The number of chromosomes is always the same among individuals of the same species but it varies from one species to another.

Question 6

What is cell cycle?

Answer 6

Cell cycle is the sequence of events take place in a body cell from one cell division to the next

Question 7

Give the examples of activities for prepare for cell division in interphase

Answer 7

• synthesis of new organelles (eg. Mitochondrion, rough endoplasmic reticulum and chloroplasts)
• DNA replication, the Chromosome becomes duplicated and it consists of two identical DNA molecules
• the growth of cell to its maximum

Question 8

***important concept
Incorrect:
At the end of the interphase, the number of chromosome in a cell doubles
Correct:
At the end of interphase, each chromosome consists of two DNA molecules instead of one. The number of DNA molecules or amount of DNA molecules doubles, but the number of chromosome remains unchanged.

Answer 8

Important

Question 9

What is mitosis ?

Answer 9

• Mitosis is the nuclear division of mitotic cell division
• it involves the separation of sister chromatids of each chromosome and the equal distribution of the separated chromatids

Question 10

Name the phrases involved in mitotic cell division.

Answer 10

Interphase —> prophase —> metaphase —> anaphase —> telophase

Question 11

What is the process of prophase of mitosis ?

Answer 11

• the chromosome shorten and thicken. They become visible.

* the nuclear membrane starts to break down

Question 12

What is the process of metaphase of mitosis ?

Answer 12

• the chromosome line up in the middle of the cell along the equator
• spindle fibres attached to the chromosome

Question 13

What is the process of anaphase of mitosis ?

Answer 13

• the spindle fibres contract. The sister chromatids separate and move to the opposite pole of the cell
• the cytoplasm starts to divide

Question 14

What is the process of telophase of mitosis ?

Answer 14

• the nuclear membranes form around each group of chromosomes.
• the chromosomes uncool to become chromatin again

Question 15

What is the mechanism of cytoplasmic division in animal cells and plant cells ?

Answer 15

• In animal cells, the cell membrane snoring the centre of the cell constricts inwards until the cell separate into two
• in plant cells, the cell plate made up of new cell membranes and cell walls is formed between two daughter cells. It grows outwards from the centre of the cell, dividing the cytoplasms into two halves

Question 16

What is the importance of mitotic cell division?

Answer 16

It produces new cells which are genetically identical to their parent cell. So, the daughter cells have the same structure and perform same function.It is important for growth as it can provide new cells for the growth of multicellular organisms, repair as it provide new cells for replacing worn-out cells (eg dead skin cells) or repairing damaged tissues and asexual reproduction in some organism

Question 17

What do first and second meiotic cell division involved ?

Answer 17

•first meiotic cell division:
~pairing and separation of homologous chromosome
•second meiotic cell division
~separations of sister chromatids

Question 18

What are the stages of meiotic cell division?

Answer 18

•Meiotic cell division consists of two divisions:
~First meiotic division:
-Prophase I: Chromosomes shorten and thicken. Homologous chromosomes pair up. The nuclear membrane breaks down.
-Metaphase I: Homologous pairs line up along the equator.
-Anaphase l: The two members of each homologous pair separate and move to opposite poles of the cell. The cytoplasm starts to divide.
-Telophase I: New nuclear membranes form around each group of chromosomes.
-Cytoplasmic division: The cytoplasm divides into two equal halves.
~Second meiotic division:
-Prophase II: The nuclear membrane breaks down again
-Metaphase II: Chromosomes line up along the equator.
-Anaphase II: Sister chromatids separate. The cytoplasm starts to divide.
-Telophase Il: New nuclear membranes form around each group of chromosomes
-Cytoplasmic division: The cytoplasm divides. Four daughter cells are formed.

Question 19

What is the importance of meiotic cell division?

Answer 19

• Meiotic cell division produces haploid gametes. This ensures the restoration of the diploid number of chromosomes at fertilization.
• Independent assortment of chromosomes and crossing over produce gametes with different genetic combinations. This causes genetic variations among individuals of the same species.

Question 20

What are the similarities of meiotic cell division and mitotic cell division?

Answer 20

• DNA has replicated before the beginning of the both process
• both involve nuclear division and cytoplasmic division
• both involve the movement of chromosome and the distribution of chromosome among daughter cells