Question

Sickle cell disease is a genetic disorder that gives red blood cells a crescent shape instead of the typical disk shape. This genetic disease is recessive. If two individuals who have one recessive gene have four children, what percentage of the children will show symptoms of sickle cell disease?

-25 percent

-100 percent

-50 percent

-75 percent

Answer 1

ok, so since both parents have one recessive gene, each one is a carrier and this is the Punnett square for their offspring

SS = two dominant alleles, non-carrier, no symptoms
Ss = one recessive allele, carrier, no symptoms
ss = two recessive alleles, has disease, shows symptoms

what percentage of the 4 children will show symptoms?