Genetic Disorders

What are they?

• A disease that is caused by an abnormality in a person’s DNA.

Types of Disorders

• Single Gene Disorders– A mutations causes the protein product to be

altered or missing

• Chromosomal Abnormalities– Entire chromosomes, or large segments of them

are missing, duplicated, or altered.

• Multi-factorial Disorders– Result from mutations in multiple genes coupled

with environmental causes

Single Gene Disorders Cystic Fibrosis

• Recessive disorder

• Usually helps move salt into & out of the cell

• When defective it causes a thick, sticky mucous to be made

• Causes issues with digestive system & lungs

Single Gene DisorderSickle Cell Anemia

• Recessive gene

• Causes red blood cells to be rigid & concave

• They are not able to transport oxygen very well (hemoglobin)

• Resistant to malaria

Single Gene DisorderHuntington’s Disease

• Dominant disease

• Causes brain cells to be destroyed that deal with movement, emotion, & thinking

Single Gene DisorderPKU

• Phenylketonuria (recessive)

• Codes for an enzyme in the liver that breaks down the amino acid phenylalanine

• Causes phenylalanine to build up in the blood which poisons brain cells (neurons)

• Can’t eat protein!

Chromosome AbnormalitiesNon-Disjunction Disorders

•When homologous chromosomes or chromatids do not separate during meiosis

•Results in –Monosomy – only one copy of a chromosome–Trisomy – having 3 copies of a chromosome

Turner’s Syndrome

–Only affect females

–X (missing X)

–Female appearance

–Infertile

–Don’t mature

Klinefelter’s Syndrome

–Only affects males

–XXY (extra X)

–Some female characteristics

–Very little facial hair

–Infertile (don’t produce sperm)

Down Syndrome

– Trisomy of chromosome 21

– Causes too much protein to be made, which causes problems

Sex-linked or X-linked Traits

• More genes can be carried on the X chromosome than the Y

• Genes ONLY on X chromosomes are called “X-linked”

• Since there is only one allele, the phenotype of that allele is expressed in males

Examples