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Dominant Inheritance
When a trait is dominant, only one allele is required for the trait to be observed. A dominant allele will mask a recessive allele, if present. A dominant allele is denoted by a capital letter (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.
One example of a dominantly inherited trait is the presence of a widow’s peak (a V-shape) at theÂhairline. 
Let (W) represent the dominant allele, and (w) represent the recessive allele. An individual with a (WW) or (Ww) genotype will have a V-shaped peak at the hairline. Only ww individuals will have a straight hairline.ÂTo 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 one parent is hom*ozygous dominant (WW) and the other is hom*ozygous recessive (ww), then all their offspring will be heterozygous (Ww) and possess a widow’s peak.ÂIf both parents are heterozygous (Ww), there is a 75% chance that any one of their offspring will have a widow’s peak (see figure). A Punnett square 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 affected individual must have an affected parent. Dominantly inherited traits do not skip generations. Lastly, males and females are equally likely to receive a dominant allele and express the trait. In this pedigree both heterozygous and hom*ozygous individuals are affected since the trait is dominant.
CLICK HEREÂto learn more about patterns of inheritance
CLICK HEREÂto learn more about recessive inheritance
CLICK HEREÂto learn more about X-linked inheritance
