Bio Project

X-linked inheritance,

X-linked recessive
a pattern of inheritance in which the transmission of a recessive allele on the X chromosome results in a carrier state in females and characteristics ofan abnormal condition in males.(powerpoint def.)
(Explanation to class) Affected people have unaffected parents (except for the rare situation in which the father is affected and the mother is acarrier). One half of the female siblings of an affected male carry the trait. Unaffected male siblings do not carry the trait. Sons of affected males are unaffected, and daughters of affected males arecarriers. Unaffected male children of a carrier female do not carry the trait.
X-linked inheritance means that the gene causing the trait or the disorder is located on the X chromosome.(explanationto class the definition of x-linked inheritance)

In this example, a woman with an X-linked dominant condition has an affected daughter, an affected son, an unaffected daughter, and an unaffectedson.

(explanation to class)
Remember, females have two X chromosomes, while males have one X and one Y. Genes on the X can be recessive or dominant, and their expression in females and males isnot the same because the genes on the Y chromosome do not exactly pair up with the genes on the X. X-linked recessive genes are expressed in females only if there are two copies of the gene (one oneach X chromosome). However, for males, there only needs to be one copy of an X-linked recessive gene in order for the trait or disorder to be expressed. For example, a woman can carry a recessive geneon one of the X chromosomes unknowingly, and pass it on to a son, who will express the trait. |
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Therefore, half of the daughters have the gene and can pass it to the next generation. The otherhalf do not have the gene and, therefore, cannot pass it on. Half of the sons do not have the gene and cannot pass it on. The other half of the sons have inherited the gene and will express the...