Alleles, genotypes and phenotypes

alleles and genotypes
1. chromosomes in all cells, except for the sex cells, come in pairs. This means the cell has two copies of every gene.
  1. The alternative genes for each characteristic are called ALLELES. the combination of two alleles in a fertilised egg id called the GENOTYPE.
if the two chromosomes have the same alleles for a certain gene, the genotype HOMOZYGGOUS.
1. if the two chromosomes have different alleles for the gene, the genotype is HETEROZYGOUS.
Dominant or recessive?
1. if the alleles are different, the DOMINAT alleles 'trumps' RECESSIVE alleles
  1. so if the dominant allele is in the genotype this characteristic will be shown in the phenotype
    1. we write the genotype as a pair of letters of the pair of alleles. a dominant allele is given a capital letter and recessive allele is given a lower- case
Flower colour is controlled by a single gene. let R represent the dominant allele for red petals and r the recessive allele for white petals. the table below show the possible genotypes and phenotypes for these allele

Resource summary

	Created by leahturner1999 over 12 years ago