Lecture 12: Principles of Genetic Inheritance Flashcards
What is the term for a disease allele on the X chromosome in males?
hemizygous
- females rarely affects, if homozygous: lyonization occurs in development (X-inactivated)
Mitochondrial DNA and mutations
- mitochondria inherited exclusively through maternal line
- mutation rate 10x higher than nDNA (no DNA repair mechanisms)
Leber’s Hereditary Optic Neuropathy (LHON)
- degradation of retinal ganglion cells
- affects NADH dehydrogenase
- acute or subacute loss of central vision
Myoclonic Epilepsy and Ragged Red Fibers (MERRF)
- mutations in gene encoding tRNA for lysine
- disrupts cytochrome-c oxidase
- ataxia and seizures, affects muscles and nerves
Mitochondrial Encephalomopathy, Lactic Acidosis, Stroke-like episodes (MELAS)
- most common maternal inherited mito disease
- affects brain, nervous system, muscles
- stroke/dementia
Polyploidy vs Aneuploidy
Poly: cells have complete set of extra chromosomes
Aneuploidy: missing/have additional individual chromosome
NONDYSJUNCTION
Uniparental disomy
- person gets two copies of chromosome from one parent and none from the other parent
Genomic Imprinting
- essentially gene silencing (methylation 5’ gene region)
- germ cells: imprints are reset at each generation (meiosis –> erased and new ones set)
Inversion, Deletion, Duplication, Translocation
- inversion: DNA segment in reverse orientation
- deletion: segment lost
- duplication segment copied, gene amplification
- translocation: two different chromosomes exchange DNA segments
Reciprocal vs Robertson Translocation
- Reciprocal: nonhomologous material exchange
- Robertsonian: long arm of acrocentric chromosome combined, short arm lost
Turner Syndrome
Karyotype: 45, XO
- monosomy X, no Y chromosome
- premature ovarian function, no puberty, infertile, webbed neck, CV defects
Prader Willi and Angelman Syndromes
- deletion of chromosome 15 region
Paternal: PW
- short stature, small hands/feet, obese, uncontrolled eating
Maternal: Angelman
- intellectual disability, seizures, ataxic gait
Klinefelter Syndrome
Karyotype: 47, XXY
- primary hypogonadism, small/undescended testies, infertility, tall
- variability in X numbers increase symptoms
Downs Syndrome
Karyotype: 47, XX+21 (Trisomy 21)
- most common (associated w/inc. maternal age)
- cardiac defects, duodenal atresia
Edwards Syndrome
Karyotype: 47, XX+18 (Trisomy 18)
- 95% die in utero (<10% live to 1 yo)
- microencephaly, small mouth/jaw, cleft lip/palate, overlapped fingers