New News Biology #55

Family Trees / Family Pedigrees

The following is a family tree for the recessive inherited disorder cystic fibrosis:

Let us label the allele for cystic fibrosis a ‘f’, while the allele for a normal would be ‘F’.

As cystic fibrosis is a recessive inherited disorder, two cystic fibrosis alleles (ff) are needed for the person to have cystic fibrosis.

However, when either Ff (heterozygous) or FF (homozygous dominant) is the case, then the person will not have the disorder.

In the case that the person is heterozygous, although they wouldn’t have the disorder, they would be considered a ‘carrier’ of the disorder, because they carry the allele, and may pass it down to their children.