Topic: Variation L1: Genetic Variation Learning Objectives: 1.Describe the two types of variation, genetic and environmental. 2.Explain how genetic information is passed from parent to offspring. 3.Compare and contrast different forms of reproduction.

Variation = differences between organisms Genetic variation = differences caused by genes Environmental variation = differences caused by the environment Examples: Genetic variation only: blood type, eye colour, genetic diseases Most variation is caused by both. Both: height, weight, skin colour

How is genetic information transferred? DNA Chromosome Nucleus Gene Cell Can you put these in order from smallest to largest?

How is genetic information transferred? Gene  DNA  Chromosome  Nucleus  Cell A gene is a section of your DNA. It contains the instructions to control one feature (eg. eye colour). DNA is the name of the chemical that carries genetic information. Chromosomes are long molecules coiled together made of DNA. Chromosomes are stored inside the nucleus of the cell.

Gene  DNA  Chromosome  Nucleus  Cell

Half of the genes comes from each parent Chromosomes come in pairs. One chromosome is from the father and one is from the mother. Each chromosome carries the same genes. This means that you get two sets of each gene. The unique combination of these genes makes you unique!

Different forms of the same gene Allele = different forms of the same gene Example: The gene for eye colour can come in two different forms (alleles), one for blue eyes and one for brown eyes. Genes can be represented by a letter and the different alleles are represented by either an uppercase letter (B) or a lowercase letter (b).

One allele come from each parent You receive one allele from each parent, forming a two allele combination (BB, Bb, or bb). Dominant allele = this allele will always cause the dominant trait Recessive allele = this allele will only show the recessive trait if both alleles are recessive (rare trait) Example: BB and Bb shows the dominant trait. bb shows the recessive trait.

Reproduction Sexual reproduction = genetic information from two organisms is combined to produce offspring which are genetically different from both parents Asexual reproduction = when cells divide to produce two genetically identical cells

Sexual Reproduction Gametes = sex cells that contain exactly half of the chromosomes Examples: sperm, ovum, pollen (plants) It is random which form of the gene ends up in the gamete 1.Organisms produce gametes. 2.Fertilisation = the gametes fuse to form a cell with a full set of chromosomes 3.Cell division makes new cells to form a new organism

Asexual Reproduction Asexual reproduction produces cells that are identical. This is how plants and animals grow and repair. Some organisms can reproduce to produce offspring that are genetically identical to the parent.