Genes and Alleles

Genes Our DNA contains thousands of genes A gene contains all the information and instructions for a particular trait (ex. hair colour, eye colour)

Alleles If the gene is responsible for hair colour, the allele would tell you what colour the hair should be Each gene can have multiple alleles Gene for Eye Colour

Aren’t our alleles the same? NO! The genes are in the same spot on each chromosome, but you could have different alleles on each chromosome! Gene for Eye Colour Chromosome from mom Chromosome from dad

Dominance Some alleles are DOMINANT over others For example, – Brown eyes is dominant to blue eyes – Even if you are Bb (genotype), your eyes will be brown (phenotype) Alleles that are not dominant are called RECESSIVE

Two new terms… Genotype Describes the alleles for each gene BB (two brown eye alleles) Bb (one brown eye; one blue) bb (two blue eye alleles) Phenotype The physical appearance that is seen in the individual Brown eyes Blue eyes We use a capital letter to represent a Dominant allele and a lower case letter to represent a recessive allele.

Homozygous- the two alleles ARE the same – Example: BB or bb Heterozygous- the two alleles are NOT the same – Example: Bb

Genes and Alleles Worksheet