Pedigree Analysis, Applications, and Genetic Testing

Vocabulary based on Chapter 6 of Pierce's Genetics: A Conceptual Approach, covering pedigree analysis, inheritance patterns, twin studies, and genetic testing methods.

Pedigree

A pictorial representation of a family history; a family tree that outlines the inheritance of one or more characteristics.

Proband

The person from whom a pedigree is initiated; the first affected family member coming to the attention of a geneticist.

Consanguinity

Mating between related persons, represented in pedigrees by a double line between a male and female.

Autosomal Recessive Trait

A trait that usually appears in both sexes with equal frequency, tends to skip generations, and is more likely to appear among the progeny of related parents.

Tay-Sachs Disease

An autosomal recessive condition caused by a missing enzyme that breaks down a certain lipid, which then accumulates in the brain.

Autosomal Dominant Trait

A trait that usually appears in both sexes with equal frequency; affected persons have at least one affected parent, and the trait does not skip generations.

Hypercholesterolemia

An autosomal dominant disorder involving the LDL receptor where the homozygous condition is more severe than the heterozygous condition.

X-linked Recessive Trait

A trait that appears more frequently in males; affected sons are usually born to unaffected (carrier) mothers, and it is never passed from father to son.

X-linked Dominant Trait

A trait that does not skip generations; affected fathers pass the trait to all their daughters and none of their sons, while heterozygous affected mothers pass it to approximately half of their sons and half of their daughters.

Y-linked Trait

A trait that appears only in males and is passed from an affected father to all of his sons.

Genetic Mosaicism

A condition where an individual has two or more sets of genes due to an error in mitosis, which can occur in early zygote formation or later.

Dizygotic Twins

Nonidentical twins.

Monozygotic Twins

Identical twins.

Concordant Trait

A trait that is shared by both members of a twin pair.

Concordance

The percentage of twin pairs that are concordant for a specific trait.

Amniocentesis

A prenatal test performed during weeks 15–18 of pregnancy where a needle is used to withdraw amniotic fluid for chemical, DNA, or chromosomal analysis of cultured fetal cells.

Chorionic Villus Sampling (CVS)

A prenatal test performed during weeks 10–12 of pregnancy where a catheter removes a small piece of the chorion for genetic testing; it has a higher risk of complications than amniocentesis but does not require cell culturing.

Heterozygote Screening

A form of genetic testing used to determine if a person is a carrier for a recessive genetic disease.

Pharmacogenomics

The study of how genes control an individual's response to medication, such as in the case of the blood-thinner Warfarin.

Genetic Information Nondiscrimination Act (GINA)

A law passed in 2008 to protect individuals from discrimination by employers and health insurance companies based on genetic information.