inherited disorders (AP Bio chpt 14&15)

Tay-Sachs disease

inherited disorder in humans that makes them unable to metabolize certain lipids - crucial enzyme doesn’t work

• these lipids build up in the brain

heterozygotes’ enzyme level is intermediated between homozygous dom. and recessive

• biochemical lvl: incomplete dominance

• molecular lvl: codominance

cystic fibrosis

affects 1/2,500 ppl in US (1/25 Europeans are carriers)

• causes mucus coating cells to be thicker than normal

example of pleiotropy

sickle-cell anemia

organismal level: incomplete dominance

molecular level: codominant

achondroplasia

form of dwarfism, affects 1 out of 25,000 in the US, dominant

huntington’s disease

also dominant, allele at locus near tip of chromosome 4, lethal

duchenne muscular dystrophy

affects 1 of 5,000 males; absence of muscle protein (dystrophin) on X chromosome (sex-linked!)

hemophilia

also X-linked recessive - causes the absence of 1 or more proteins needed for blood clotting

affected a lot of royal families (inbreeding)

down syndrome

usually trisomy 21 (total 47 chromosomes); frequency increases with age of mother

klinefelter syndrome

XXY (extra X chromosome in male) → testes are small and make little to no sperm

Trisomy X

XXX, 1 of 1,000 live female births, generally healthy

Turner syndrome

1/2,500 female births; only viable monosomy in humans (XO)

Cri du chat

deletion in chromosome 5

chronic myelogenous leukemia (CML)

reciprocal translocation in mitosis of white blood cell precursors

large portion of chromosome 22 with tip of chromosome 9 → philadelphia chromosome (in chrom. 22)