KEY TAKEAWAYS •
There are 22 pairs of autosomal genes and two sex-linked genes in the human chromosome.
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Chromosomal abnormalities lead to missing chromosomes, extra chromosomes, deletions or additions to chromosomes.
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Many chromosome abnormalities are not directly inherited but are caused by defects in meiosis.
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Many chromosomal abnormalities lead to mental retardation; however, Turner syndrome is not one of them.
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Autosomal dominant disorders are passed on in each generation to half of the affected person’s children.
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Autosomal recessive disorders involve a carrier state that is an unaffected person who passes the disease on only if the other parent is also a carrier or has the disease.
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X-linked recessive traits involve a variety of diseases that do not affect girls nearly as much as boys. Girls are often carriers of the disease.
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