Summary

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Chapter: Anatomy and Physiology for Health Professionals: Heredity

The field of genetics studies how children inherit traits from their parents and relatives as determined by DNA.


Summary

The field of genetics studies how children inherit traits from their parents and relatives as determined by DNA. While a karyotype is a representation of a person’s chromosomes, his or her complete genetic complement is the genome. The combination of varying forms of genes, called alleles, makes up a person’s genotype. When an allele pair is identical, the individual is homozygous for that trait. When alleles are different, the individual is heterozygous. A genotype is the actual genetic makeup of cells. A phenotype is the way in which these genes are expressed. Genetic variation occurs because of inde-pendent assortment, homologue crossover, and random fertilization.

Patterns of inheritance through families are called modes of inheritance, which include autoso-mal recessive, autosomal dominant, and X-linked recessive. Genetic disorders usually reflect homozy-gous recessive conditions. Carriers are heterozygotes that do not express a trait but can pass it to their offspring. Traits determined by genes on the X and Y chromosomes are called “sex-linked traits.” Gene expression can be influenced or overridden by envi-ronmental factors. Inheritance may be determined by factors other than nuclear DNA sequence, which include protein-­coding genes, RNA-only genes, and epigenetic marks. Advances in genetics, including the outstanding results of the Human Genome Proj-ect, are improving treatments and even cures for a large variety of diseases and disorders linked to gene and chromosomal defects. Procedures used to check for genetic conditions include pedigrees, amniocen-tesis, CVS, and blood tests.

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