Intro to Med Genetics Flashcards
How can be medical genetics be divided up?
Two clinical fields (clinical genetics and genetic counseling); three lab sciences (cytogenetics, molecular genetics, and biochem genetics)
What is a mutation? What do mutations allow for?
Permanent, heritable change in sequence of genomic DNA; can give rise to new alleles to allow for adaptation to environment
What are examples of neutral, positive, and negative mutations?
Neutral: blue eyes
Positive: sickle cell trait in countries with malaria endemic
Negative: sickle cell disease; cancer
What are patterns of inheritance?
Dominant vs. recessive
X-linked vs. autosomal
What is inherited gene complement compared to acquired gene complement?
Inherited: mutations from one or both parents (constitutional genome)
Acquired: single mutation gives rise to cells via clonal propagation (potentially deleterious; later in life)
To be diagnosed with something, what must an individual have?
Core group of cardinal characters associated with that disease (range of variability)
Biochemical genetics deals with what?
Inborn errors of metabolism (diagnosis, treatment, research)
What is an inborn error of metabolism?
Deals with a specific enzyme defect producing a metabolic block: 1. substrate accumulation 2. product deficiency
Almost always recessive
How is tyrosine converted to melanin?
Tyrosine to pigment A through tyrosine oxidase; pigment A to melanin through “Enzyme X”
How do you get a grey/brown cat? An albino cat?
Block at “Enzyme X;” block at tyrosine oxidase
What are two types of albinism?
Complete (red eyes)
Partial (some organs/tissue have pigment, like blue eyes of cat or brown eyes of boy)
What is deficiency of shared enzyme?
Enzyme might function in multiple different related or unrelated pathways
What are general features of an inborn error of metabolism?
Mental retardation, poor growth, general metabolism issues, neurological problems
What are three examples of hyperphenylalaninemia?
PKU, variant PKU, tetrahydrobiopterin metabolism defects
What is PKU? How is it inherited?
Phe hydroxylase deficiency, allowing for buildup of phenylpyruvic acid which is detected in the urine
Autosomal recessive
How can PKU be treated?
Diet modification for kids early in life and pregnant women, since Phe can cross placenta to fetus and damage it
How is non-PKU hyperphenylalaninemia compared to PKU? What about variant PKU relative to those two?
Non-PKU: deficit in Phe hydroxylase, but less damaging and might not require special diet
Variant: between the other two; might require diet, but not as restrictive as full-on PKU
If someone has a BH4 metabolism defect, how can it be treated?
For Phe hydroxylase, add BH4 to supplement orally
To make dopamine from tyrosine, and serotonin from tryptophan, L-dopa or OH-trp are needed
What are 3 characteristics of lysosomal storage diseases?
- Recessive
- Macromolecules cannot be degraded in lysosomes as lysosomal hydrolytic enzymes are mutated
- Progressive degeneration
What can lead to GM2 gangliosidoses?
Mutations in three different genes that produce 3 proteins that function together (alpha, beta subunits and activator)
What are characteristics of Tay Sachs?
Autosomal recessive, Ashkenazi Jews susceptible; hexosaminidase A defect; GM2 gangliosides can’t be degraded; cherry red spot in retina; can’t walk; die between 2 and 4
What builds up in mucopolysaccharidoses? Why?
Mucopolysaccharides or GAGs (repeating chains of disaccharides)
Specific enzyme needed to cleave the monosaccharide absent/defective
What are some characteristics of mucopolysaccharidoses?
Permanent; progressive; short, delay, skeletal abnormalities, joint stiffness, thickened skin, heart, liver, spleen damage
What is a major CT disorder with respect to collagen?
Osteogenesis imperfecta
What is OI due to? How is it inheritied? What are the major characters?
Mutations in type I collagen
Autosomal dominant
Brittle bones and skeletal deformities
Which OI type is the worst?
OI II (perinatal lethal) > OI III > OI IV (mild-moderate bone deformity and fracturing)
What is Ehler-Danlos syndrome due to?
Mutations in different collagen genes leading to post-translational mod errors of collagen
For Ehler-Danlos, what are the subtype characteristics?
Skin fragility (scarring); joint hypermobility; skin hyperextensibility/elasticity
What is Marfan syndrome attributed to?
Fibrillin gene mutations
Where are defects in Marfan’s seen?
Myopia, lens dislocation, cataracts, glaucoma, retinal detachment; dilatation and dissection of aorta; lung problems; joint laxity, scoliosis, tall, thin, long thin fingers
How can Ehler-Danlos syndrome be inherited?
Autosomal recessive, dominant; X-linked recessive
