Variation and inheritance

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Discrete and continuous Variation

Differences that can be seen between individual members of a species are called variation.

Discrete - The differences are clear-cut and show a discontinuous pattern. E.g tongue rolling someone can either do it or not it is clear cut

Continuous - There is a range of variation between extremes. The characteristic is polygenic (there is many different genes involved). Most features of an individual's phenotype (the visible characteristics) e.g height which shows a range as some people are tall and someone people are small.

What is a gene?

A gene is single piece of genetic information made from DNA. It carries the information to create a particular characteristic. Genes exist in different forms called alleles.

Alleles - a form of gene

Alleles are given symbols usually letters to make working with easier.

Homozygous - has two alleles the same

Heterozygous - two alleles are different

Genotype - the alleles an organism has for a particular characteristic usually written as symbols.

Dominant - Form of a gene they always show up in the phenotype of a plant. Have a capital letter.

Recessive - Alleles only show up is they have two copies

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