11/09/12

Heredity: Inheritance and Variation

by: Mark Alcazar ................................................

11/09/12VariationVariation is a name given to differences in a species, e.g. dogs:

Variation is due to each animal having different GENETIC INFORMATION in their cells.

11/09/12Where is this information stored?

Section of a chromosome:

Genes for eye colour

Genes for hair

colour

Genes for blood group:

Different species have different numbers of chromosomes. Humans have 46 (23 pairs) in every cell.

Genetic information is stored by genes which are arranged on chromosomes:

11/09/12Environmental differencesClearly, not all differences are due to just our genes…

Variation due to inheritance only

Variation due to environment only

Variation due to a bit of both

11/09/12Sexual reproductionSexual reproduction involves two organisms of the same species. Each organism produces a GAMETE.

For example, in animals the gametes are the egg and the sperm:

When the sperm penetrates the egg the egg is fertilised and cells start to reproduce to form a new individual:

11/09/12Sexual reproductionIn plants, the gametes are the egg and pollen:

Any type of sexual reproduction helps a species to become more varied because the offspring inherit characteristics from both parents.

Fertilization

11/09/12Selective breedingI raise cows. Each type of cow is good at a certain job. The Friesian cow

produces large quantities of milk, the Jersey cow produces very nice milk and the Hereford cow produces lot of beef.

If, for example, I want lots of milk I would only breed Friesian cows with each other – this is SELECTIVE

BREEDING.

Friesian

Jersey

Hereford

11/09/12Asexual reproductionPlants can reproduce ASEXUALLY. The offspring are genetically ________ to the parent plant and are called _________. Two examples:

1) This spider plant has grown a rooting side branch (“stolon”) which will eventually become __________.

2) A gardener has taken cuttings of this plant (which probably has good characteristics) and is growing them in a ____ atmosphere until the ____ develop.Words – clones, damp, independent, roots, identical

11/09/12Cloning1) Cloning plants:

2) Cloning sheep: