Cell Division

Question 1

What are chromosomes made up of?

Answer 1

Consists of DNA molecules combined with proteins. They contain genes which provides the instructions for protein synthesis.

Question 2

Cell Cycle Stages

Answer 2

1. During the cell cycle the genetic material is doubled and then
   divided into two identical cells.
   Before a cell can divide it needs to grow and increase the number
   of sub-cellular structures such as ribosomes and mitochondria. The
   DNA replicates to form two copies of each chromosome. (this is the LONGEST stage)
2. Mitosis- one set of chromosomes is pulled to each end of the cell. The nucleus also divides.
3. The final stage of the cell cycle- the cytoplasm and cell membrane aslo divides to form two identical daughter cells

Question 3

Functions of mitosis

Answer 3

• Essential for growth and development of multi-cellular organisms (e.g. plants and animals)
• Mitosis takes place when an organism repairs itself (e.g. when a broken bones heals)
• Happens during asexual production.

Question 4

Stages of meiosis

Answer 4

Students should be able to explain how meiosis halves the number
of chromosomes in gametes and fertilisation restores the full
number of chromosomes.
Cells in reproductive organs divide by meiosis to form gametes.
When a cell divides to form gametes:
* copies of the genetic information are made
* the cell divides twice to form four gametes, each with a single
set of chromosomes
* all gametes are genetically different from each other.
Gametes join at fertilisation to restore the normal number of
chromosomes. The new cell divides by mitosis. The number of cells
increases. As the embryo develops cells differentiate