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.
phenotype and genotype
- development will only occur if a given gene is turned on and off at the correct time, in the right place and for the right length of time
- some genes are only turned on in a few cells and for only a few hours and then switched off permanently
- other genes= basic functioning of almost all cells
regulator genes control the switching on switching off of genes
phenotype acnd genotype
external factors= can affect the switching on and off of genes
- there is a continuous interaction between the environment and the genotype
the range (norm) of reaction
refers to all the phenotypes that could theoretically result from a given genotype, given all the envuronemnts in which it would survive and develop
range of norm- plants
three cuttings (genetically identical) taken from 7 plants, planted at different elevations.
- the phenotype is the unique consequence of a particular genotype in a particular environemnt
phenotype and genotype
- a child with a given genotype develops differently in a loving gamily compared to abusive
- the child actively creates and explores the environment where they live
- by virtue of nature, they evoke different responses
epigenetics
genome
recors of the genetic material of an organism encoded in DNA
epigenome
record of the chemical changes to the DNA and histone proteins of an organism
heritable
but reversible changes in gene expression that are not coded in the DNA sequence but by post-translational modifications in DNA< histone proteins are in micro RNA
autoimmune disorders
they affect 7% of the population, it is not completely genetic so there is a role in the environment because some twins will have the disease while others wont.
- more females are affected than males and more likely away from equator.
