Topic 3: Human Genetics

Pedigree analysis

Family tree that describes the phenotypes & relationships of parents & children across generations. Allows for predictions about future offspring

Autosomal recessive disorder

Disorder expressed only when two recessive alleles are present; carriers are heterozygous. (Ex; tay-sachs, cystic fibrosis, & sickle-cell.)

Autosomal dominant disorder

Disorder expressed with one dominant allele; often rare due to selection. (Ex; Achondroplasia, Huntington's disease)

X-linked recessive disorder

Disorder caused by recessive allele on X chromosome. Males cannot be heterozygous, females can be homozygous or heterozygous (carrier).

Carrier

Individual with one recessive allele who does not show symptoms but can pass it on.

Sickle cell disease

Autosomal recessive disorder causing abnormal hemoglobin and misshapen red blood cells.

Cystic Fibrosis

Autosomal recessive disorder affecting CFTR gene, leading to thick mucus in lungs.

Hemophilia A

X-linked recessive disorder causing impaired blood clotting.

Huntington’s Disease

Autosomal dominant mutation in huntingtin gene. Causes neurodegeneration & death.

Hereditary Breast and Ovarian Cancer BRCA1/2

Mutations in tumor suppressor genes that increase cancer risk. Happens on chromosomes 17 & 13.

Hereditary Nonpolyposis Colorectal Cancer (HNPCC)

Autosomal dominant disorder caused by mutations in DNA repair genes. 80% of heterozygotes develop colon cancer.

Genetic counseling

Process of advising individuals about genetic risks and inheritance.

Benign mutation

DNA change that does not affect health.

Variant of Uncertain Significance (VUS)

Genetic change with unknown effect on disease risk.

Pathogenic mutation

DNA change that increases risk of disease or causes disease.