Chap 3 & 4 Diseases/Traits

Albinism

• Autosomal Recessive Trait

• Due to mutations in gene(s) involved in melanin production

• If both parents are carriers, 1:4 chance the child will be affected

Huntington’s Disease

• Autosomal Dominant Disease

• Trait appears in every generation

• Neurodegenerative disease

• Early onset (~middle age) and death 10-20 years later

• Example of lethal allele

Achondroplasia

• Autosomal Dominance Trait

• Cause by mutations in FGFR3 gene, leads to improper conversion of cartilage into bone

• ~80% of cases are not inherited

• Homozygous dominant die before or shortly after birth

• Very rare to have two mutant copies

Polydactyly

• Autosomal dominant trait

• Example of Incomplete Penetrance

• Cause additional fingers and/or toes

• Can have low (1 extra finger) or high expressivity (3 extra toes)

Sickle-cell anemia

• Autosomal recessive disorder

• Example of heterozygote advantage

• Affected individuals produce abnormal form of hemoglobin

ABO blood groups

• Example of multiple alleles in natural populations

• Determined by the type of antigen present on the surface of red blood cells

Duchenne muscular dystrophy

• X-linked recessive disorder

• Females need two copies of mutant gene and makes only need one

• rapid degeneration of muscles; mutated dystrophin protein

Cystic fibrosis

• Example of pleiotropy

Manx cat

• Autosomal Dominant trait

• Example of a lethal allele

• mutation that causes shortening of tail

• Homozygous dominant is lethal; heterozygous is not