Name:__________________ Date:_________
Genetics Problems (www.biologycorner.com)
Sickle Cell Disease (SSD) is caused by a recessive allele that is codominant and is located on chromosome 11.
Those who have both recessive alleles (aa) have abnormally shaped blood cells that do not efficiently carry
oxygen and can become stuck in blood vessels. Blood cells can stick together and form clots, increasing the
risk for strokes and causing extreme pain in joints and muscles. Heterozygotes (Aa) have a few sickle-cells, but
many blood cells are normal shaped and are said to have “sickle cell trait.”
1. Show the cross between two parents who are both heterozygous for the trait.
What percentage of their children will have the disease (aa)?
_HbA_
_ Hba_
_ HbA _
% Normal
% Trait
SSD
_ Hba_
2. If a person has sickle cell disease and is married to someone who is a carrier, What percentage of
offspring will likely have the disease?
__
__
% Normal
__
% Trait
SSD
__
Q3. A plant that has red flowers (RR) is crossed with a plant that has pink flowers (Rr). What portion of the
offspring is expected to have pink flowers?
a. ¼
Biology
b. ½
c. ¾
d. 1/8