Human Genetics & Complex Inheritance

This set of flashcards covers key concepts related to human genetics and complex inheritance, explaining various genetic inheritance patterns, disorders, and methods of fetal DNA analysis.

Autosomal Recessive Disorders

Disorders that are more common because dominant mutations are usually expressed and eliminated, while recessive alleles can remain hidden in carriers.

Carrier

A person who is heterozygous (Aa) for a recessive allele, does not show symptoms, but can pass the allele to offspring.

Predicting Recessive Disorder Inheritance

AA × AA results in 0% affected, Aa × Aa results in 25% affected, Aa × aa results in 50% affected, and aa × aa results in 100% affected.

Predicting Dominant Disorder Inheritance

Dd × dd results in 50% affected, DD × dd results in 100% affected, and Dd × Dd results in 75% affected.

Pedigrees

A diagram showing inheritance patterns, with autosomal recessive skipping generations, autosomal dominant appearing every generation, and X-linked recessive affecting mostly males.

Examples of Autosomal Recessive Disorders

Cystic fibrosis, PKU, Tay-Sachs, and Sickle-cell disease.

Examples of Autosomal Dominant Disorders

Huntington’s disease, Achondroplasia, and Marfan syndrome.

Heterozygote Expression

The phenomenon where the expression can show complete dominance (Aa = dominant phenotype), incomplete dominance (Aa = intermediate blend), or codominance (both alleles expressed).

Multiple Alleles

A situation where more than two alleles exist for a gene in a population, demonstrated by the ABO blood system.

Pleiotropy

The ability of one gene to affect multiple traits.

Polygenic Inheritance

Inheritance where many genes influence one trait, seen in characteristics like height and skin color.

Human Sex Determination

The genetic designation of XX for females and XY for males, with SRY gene triggering male development.

Sex-linked Inheritance

Inheritance patterns for genes located on the X chromosome, which affect males more often.

Chromosomal Errors

Errors such as nondisjunction leading to conditions like Trisomy or Monosomy.

Karyotype

A chromosome map that shows the number, size, and shape of chromosomes, used to detect trisomies and large chromosomal rearrangements.

Fetal Cell Collection for Karyotype

Techniques such as amniocentesis, Chorionic Villus Sampling (CVS), and non-invasive maternal blood testing to collect fetal cells for analysis.