1. Chapter 14 Cell Division

2. Cells spend very little time involved in cell division they spend most of their time chemicals/substances they need to survive and grow.
Chromosomes – Are coiled threads of DNA (which forms genes) and protein that become visible in the nucleus at cell division.
Chromatin – Long thin threads of DNA which is found in
the nucleus of cells that are not dividing.
Every species has a definite number of chromosomes
e.g. humans have 46 chromosomes (23 pairs)
in every cell except the gametes
(sperm & egg cells) which have 23
Chromosomes in the nucleus of their cell.
Each chromosome is composed of hundreds
or thousand of genes arranged along the
chromosome.

3. Genes
A gene is a section of DNA that contains the instruction for the formation of a protein.
Many of the proteins produced by genes are enzymes. Genes are the units of inheritance.
All the genes in an organism make up its genome.
In humans genes control features such as eye colour, number of fingers etc. In plants genes control features such as petal colour, fruit taste etc.
Haploid and Diploid Cells

13. Detailed Study of Mitosis

19. Causes of Cancer
Cancer is when normal genes are altered to cancer causing genes called oncogenes. These alterations are brought about by cancer causing agents called carcinogens. Common carcinogens include cigarette smoke and uv light. Most cancers can be cured particularly if they are diagnosed early.

21. Meiosis Allows for Variation
The cells resulting from meiosis are not identical. Their genes vary due to the exchange of genetic material which takes place during meiosis. This is why brother s and sisters resemble each other but are not identical.

22. Cell Division in an Animal Cell
Cell Division occurs after mitosis. In animal cells a shallow groove called a cleavage furrow grows. It grows deeper and divides the cell in half. This is called cytokinesis. The new cells are called daughter cells.