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X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome. As an inheritance pattern, it is less common than the X-linked recessive type.
We will mostly consider five major types of inheritance: autosomal dominant (AD), autosomal recessive (AR), X-linked dominant (XD), X-linked recessive (XR), and Y-linked (Y) inheritance. We generally make two assumptions in analyzing Pedigree Charts.
X linked Dominant Inheritance. Male and female both are affected, but females are affected in excess and less severely. Affected males can transmit the mutant allele to female offspring but not to male offspring.
Several basic modes of inheritance exist for single-gene disorders: autosomal dominant, autosomal recessive, X-linked dominant, and X-linked recessive. However, not all genetic conditions will follow these patterns, and other rare forms of inheritance such as mitochondrial inheritance exist.
X-linked dominant and X-linked recessive inheritance patterns are two important genetic mechanisms associated with disorders located on the X chromosome. While X-linked dominant disorders can affect both males and females, X-linked recessive disorders are more commonly observed in males.
An X-linked condition occurs when a pathogenic variant in a gene on the X chromosome leads to disease. Women have two X chromosomes (XX) and men have one X and one Y chromosome (XY). When considering X-linked inheritance, this difference between the sexes is important.
Patterns of inheritance in humans include autosomal dominance and recessiveness, X-linked dominance and recessiveness, incomplete dominance, codominance, and lethality. A change in the nucleotide sequence of DNA, which may or may not manifest in a phenotype, is called a mutation.
X-linked dominant inheritance. In X-linked dominant inheritance, the gene responsible for the disease is located on the X-chromosome, and the allele that causes the disease is dominant to the normal allele in XX individuals, who tend to be more frequently affected than XY individuals in the population because they have two copies of the X ...
Where an X-linked dominant gene variant is shown as ‘D’ and the working gene copy by ‘d’, there are several possibilities a person could have and depending on whether they are male or female, the effect of the genetic makeup will differ.
Huntington disease, Marfan syndrome, and myotonic muscular dystrophy are examples of autosomal dominant inheritance. The autosomal dominant inheritance is shown in figure 1. Figure 1: Autosomal Dominant Inheritance. Autosomal Recessive Inheritance. Both copies of genes are mutated in autosomal recessive inheritance.