variation and inheritance

• discrete variation is from single gene inheritance - in distinct groups
• continuous variation is polygenic and is a range of values
• phenotype - physical appearance
• genotype - alleles for a particular characteristic
• allele - different forms of a gene
• homozygous - having two identical alleles of a particular gene, e.g. BB
• heterozygous - having two different alleles of a gene, one from each parent e.g. Bb
• fertilisation is a random process so predicted ratios aren't always achieved