Genetic Crosses

Heredity – Crosses Introduction netics/heredity/

Dominant and Recessive

A true breeding black mouse is crossed with a true breeding white mouse. Black colour is dominant. or

A true breeding black mouse is crossed with a true breeding white mouse. Black colour is dominant. or

A true breeding brown eyed human is crossed with a true breeding blue eyed human. Brown colour is dominant. or

A true breeding brown eyed human is crossed with a true breeding blue eyed human. Brown colour is dominant.

A true breeding red flower is crossed with a true breeding white flower. Red flower colour is dominant.

A true breeding normal winged fly is crossed with a true breeding vestigial winged fly. Normal wing shape is dominant.

A true breeding black rabbit is crossed with a true breeding white rabbit. Black fur colour is dominant. Complete the cross to show the phenotypic ratio of the F2 generation.

A true breeding purple flower is crossed with a true breeding white rabbit. Purple is dominant. Complete the cross to show the phenotypic ratio of the F2 generation.

A true breeding regular thumbed human is crossed with a true breeding hitchhiker thumbed human. Regular thumb shape is dominant. Complete the cross

Eyes eColour/EyeColour.htm

WordDefinition ChromosomeLarge pieces of DNA GeneSections of a chromosome which codes for a characteristic AlleleDifferent forms of a gene dominantAllele whose effect always shows in the phenotype RecessiveAllele whose effect is hidden in the phenotype Homozygous (true breeding) Both alleles in genotype are the same e.g. BB or bb Hetero7ygousAlleles in genotype are different e.g. Bb PhenotypeThe appearance of an organism GenotypeThe alleles an organism has for a particular characteristic