Dominant Inheritance

When a trait is dominant, only ane allele is required for the trait to exist observed. A ascendant allele will mask a recessive allele, if nowadays. A ascendant allele is denoted by a upper-case letter alphabetic character (A versus a). Since each parent provides one allele, the possible combinations are: AA, Aa, and aa. Offspring whose genotype is either AA or Aa will have the dominant trait expressed phenotypically, while aa individuals express the recessive trait.

Ane example of a dominantly inherited trait is the presence of a widow's tiptop (a Five-shape) at the hairline. Let (West) represent the ascendant allele, and (west) represent the recessive allele.  An individual with a (WW) or (Ww) genotype volition have a V-shaped peak at the hairline. Only ww individuals volition take a directly hairline. To determine the probability of inheritance of a widow's peak (or any other dominant trait), the genotypes of the parents must be considered. For example, if ane parent is homozygous dominant (WW) and the other is homozygous recessive (ww), then all their offspring will exist heterozygous (Ww) and possess a widow's peak. If both parents are heterozygous (Ww), there is a 75% chance that any one of their offspring will have a widow's peak (run across figure). A Punnett square tin can be used to determine all possible genotypic combinations in the parents.

Pedigree

A pedigree that depicts a dominantly inherited trait has a few key distinctions. Every afflicted individual must have an affected parent. Dominantly inherited traits do not skip generations. Lastly, males and females are equally probable to receive a dominant allele and limited the trait. In this full-blooded both heterozygous and homozygous individuals are affected since the trait is dominant.

Image courtesy of Michael A. Kahn, DDS

CLICK Here to learn more than about patterns of inheritance
CLICK Here to learn more nearly recessive inheritance
CLICK HERE to learn more about X-linked inheritance