- A cell is the basic unit of life; all organisms are made up of cells.
- In I/GCSE Biology, the nucleus is a large organelle found in all cells, that contains the genetic information.(Even red blood cells once had a nucleus).
- DNA (Deoxyribose nucleic acid) is the chemical found in the nucleus of all cells that contains the genetic information.
- are thread-like structures made of DNA found in the nucleus
- are small sections of a chromosome that control the characteristics of an organism. Different genes control the development of different characteristics. Genes are passed on from parent to offspring, resulting in offspring having similar characteristics to their parents. eg eye colour
- There is no fusion of gametes and only one individual is needed as the parent.
- There is no mixing of genetic information and so no variation in the offspring.
- These genetically identical individuals are known as clones.
- Bacteria or yeast cells use binary fission
- Plants can use runners, bulbs or vegetative propagation.
- Humans can create plant clones using cuttings and tissue cultures.
- Some invertebrate animals like starfish, worms and hydra.
- Humans can clone other animals, eg. Dolly the sheep.
- Sexual reproduction - the joining (fusion) of male and female gametes.
- The mixture of the genetic information from two parents leads to variety in the offspring.
- Genes are passed on in the sex cells (gametes) from which the offspring develop.
The causes of variation
- Sexual reproduction - leads to variety in the offspring
- Asexual reproduction - no variation in the offspring.
How do variation occur?
- Meiosis – all gametes created by one person are genetically different.
- Random fertilisation
- Physical forces
That's the end of the topic!
Drafted by Joey (Biology)