Genetic Crosses that Involve 2 Traits

In rabbits,  black hair is dominant to brown hair.  Also in rabbits, long straight ears are dominant to floppy ears.

The letters represent the genotypes and phenotypes of the rabbits:

BB = black hair | Bb = black hair | bb = brown hair

EE = long ears | Ee = long ears | ee = floppy ears

1. A male rabbit with the genotype BBee is crossed with a female rabbit with the genotype bbEe The square is set up below. Fill it out and determine the phenotypes and proportions in the offspring.

	How many out of 16 have black hair and long ears? ______ How many out of 16 have black hair and floppy ears? ________ How many out of 16 have brown hair and long ears? ______ How many out of 16 have brown hair and floppy ears? _______
2. Show the cross: BbEe x bbee	How many out of 16 have black hair and long ears? ______ How many out of 16 have black hair and floppy ears? ________ How many out of 16 have brown hair and long ears? ______ How many out of 16 have brown hair and floppy ears? _______

3. Fruit flies are organisms commonly used in genetic studies. They reproduce quickly and have several traits that can be measured. One trait is the vestigial wing trait, which is recessive. Most flies have red eyes, but the sepia eye trait is recessive. The image shows a mutant double recessive fly (ggee)

A fly that is heterozygous for both traits (GgEe) is crossed with one that has vestigial wings and sepia eyes (ggee). Set up a Punnett square and list the phenotypic ratio of the offspring.

 

How many are normal wings, red eyes? _____

How many are normal wings, sepia eyes? _____

How many are vestigial wings, red eyes? ____

How many are vestigial wings, sepia eyes? ______

4. Show a dihybrid cross for fruit flies. GgEe x GgEe. List all the possible phenotypes and the number that is expected from this cross. Be careful when counting the number for each phenotype, it is easy to make a mistake.