In rats, the following genotypes of two independently assorting autosomal genes determine coat color as follows: A-B- (gray), A-bb (yellow), aaB- (black), aabb (cream). A third gene pair on a separate autosome determines whether or not any color will be produced. DD and Dd genotypes allow color according to the expression of the A and B alleles. However, the dd genotype results in albino rats regardless of alleles of the A and B alleles present. Determine the phenotypic ratios of the offspring from the following crosses:

AaBbDd x AaBbDd

19/36 Gray, 9/36=1/4 albino, 5/36 yellow and 3/36-1/12 Black offspring.

Explanation:

To produce a gray- A-B-

To produce yellow - A-bb

To produce black - aaB-

To produce cream - aabb

To produce any colour among the above - D-

To produce an albino - dd

A cross between two grays will give rise to  

                      AaBbDd   x     AaBbDd

 19/36 Gray, 9/36=1/4 albino, 5/36 yellow and 3/36-1/12 Black offspring

hey there!

so, when you eat, your teeth chew and grind food into smaller pieces. this is mechanical digestion. then reactions aided by digestive enzymes break down large food molecules into smaller molecules. this is chemical digestion. the two processes change the food into simpler substances that can be used by the body for raw materials and energy.

hope this

tobey