Which of the following is true for autosomal recessive alleles associated with a disease?

Choose one:
A. These alleles are seen more frequently in males.
B. Two copies of the allele are required for the individual to be affected.
C. One copy of the allele will cause the disease.
D. An individual who shows the disease must have at least one parent with the disease.

B. Two copies of the allele are required for the individual to be affected.