human genetics 2 (disorders) Flashcards
overall facts
- 5,000 human disorders are known to have genetic origins
recessive gene + single dominant gene
RG: PKU, sickle-cell anemia, tay sachs, cystic fibrosis
SDG: Huntington’s disease, neurfibromatosis
polygenic inheritance +sex-linked inheritance
PI: cancer, heart disease, asthma, psychiatric, behvaior disorders
SLI: red-green colour blindness, fragile-X syndrome
regulator gene defects, chromosomal abnormalities
RGD: genetic male with female genatalia
CA: downsyndrome, Klinefelter syndrome, turner syndrome
Tay- Sachs disease
- fatal, autosomal recessive neurodegenerative disease of infancy and early childhood
- gene tells the body to stop producing Hex-a enzyme needed to break down fatty subsance
- caused by mutations of Hex A gene chromosome
Huntington’s disease
progressive neurodegenerative disorder, autosimal dominate.
>40 repreats of cytosine, adenine and guanine in coding region of gene
- onset= 4oy/o 12-15 yrs afterwards= death
symptoms of HD
cognitive deterioration, personality change, memory loss, depression, slow movement
invoulantary movement characteristic of HD
invoulantary ‘dance like’ movement
- abates in advance stages of disease, when akinetic and bradykinetic movements become clear
voulantary characterise movement in HD
- Bradykinetic
- inconsistent and inefficient movement
- abnormal co-contractions of muscles
- prolonged EMG bursts
- less efficient and more variable movements in handwriting
- sequential and simultaneous movement difficulties
broad sub-cortical and cortical damage
- neuronal and astrocyte loss in basal ganglia
- selective degeneration of GABAergic neurons of striatum
- as disease progresses, greater cortical atrophy occurs
HD cont.
- gene contains expanded trinucleotide repeat that ranged from 9-35 in healthy adults but 36-190 for HD
- allels with 36-39 repeat how ‘reduced penetrance’- only some individuals will develop clinical symptoms
- young patiesnts= >55 repeats and develop HD before 20 y/o
- onset earlier if transmitted by father
polygenetic inheritance
- when traits are governed than more than one gene
- shifts from focusing on single gene mutation to examining the combination of many genes working together
schizo
- young adulthood= onset
- 0.5% pop affected, can be continuous or episodic
- more likley to be continuous than categorical
- genetic risk of schizo= largely polygenenic
fragile X syndrome
- FXS= most common intellectual diability
- expansion mutation of CGG repeat sequence in the FMR1 gene at the locus
- leads to the silencing of the gene and absence of the gene product
- protein is essential for brain development- brain synaptic plasticity, development
- boys= more affected than girls
Phenylketonuria
- children w PKU are unable to metabolize phenylalanine
- phenylalanine is a amino acid found in high protein food
- PKU is a disorder that is related to a defective gene on chromosome 12, which the body cannot break down and may cause damages w brain development
- early diagnosis= restricted diet can stop menta retardation.