10/16 genetics Flashcards
what is the typical inheritance of mitochondrial diseases?
they are inherited from the mother and the mother will pass it on to all of her offspring (though incomplete penetrance is posible.
what are some importanct features of mitochondrial genetic mutations?
inheritance is maternal.
Mutation rate is high.
why would the mitochondria have such a high mutation rate?
- repair is not as efficient.
- There are a lt of oxidative species in the mitochondria.
what is heteroplamsy in genetic?
mitochondrial mosaicism within cells!
why would we see expression of some mitochondria mutations in some cells but not all the cells of an individual
Heteroplasmy is very common
what are some common diseases that see mitochondrial mutation genetics
deafness type 2 diabetes alzheimer disease? parkinson disease? aging...
what is somatic cell nuclear transfer?
healthy donar egg has the nucleus removed and the “mother’s” nucleus is put in and then that is used for IVF!
what is the most common cause of pregnancy loss?
Chromosome abnormalitites
what is the most common cause of intellectual disability?
Chromosome abnormalities.
genetic term for multiple of “true number” of chromosome
Euploid
23 chromosomes
Haploid
46 chromosomes
diploid
69 chromosomes
triploid
92 chromosomes
tetraploid
Genetic term for number of chromosomes that is not a multiple of the “true number”
Aneuploid
One copy of a specific chromosome
Monosomy
Three copies of a specific chromosome
Trisomy
Compare How is the survivial for Monosomy of any chromosome to Trisomy
No survival for monosomy; but survival of trisomy is reletively common. it seems that it is better to have more than not have enough chromosomes
how did we ever get a picture of the chromosomes?
use colchicine (spindle poison) to arrest the cells in metaphase, and use a hypotonic solution to swell and break the cell and visualize the chromosomes.
what is Giemsa stain?
It is G-banded staining of chromosomes that gave them stripes by the amount of A,T that the different sections have
the image of the chromosomes of an individual by G-banding staining
Karyogram
Where are the genes in G-banded staining
in the light staining reagions (A,T poor regions)
the effects of having an extra copy of all of the chromosomes
Occipital and other skull bone problems
hypercesis
heart defects
Lethal in a short time after birth
How could we get triploid genotypes?
two sperm cells could fertilize the egg.
could also see egg cells with diploid (myotic failure)
How do Triploids usually give us a good example of imprinting effect?
Dad source of triploidy: large fetus
Mom source of triploidy: small Fetus
what are some of the major features seen in Down Syndrom?
Intellectual disability Congenital heart defects reduced stature; char. facial appearance increased risk of leukemia increased risk of repiratory infections neurohistopathology of alzheimer disease by age 40 (amyloid plaques)
why would down syndrome patients develop alzheimer by 40 years old?
Gene 21 gives beta-amyloid precursor protein gene and the over production of this probably leads to amyloid plaques!
what are the facial features of Down syndrome?
Strabismus large tounge and somewhat protrude epicanthic fold by the nose and the eye brushfield spots in the iris that gives it a speckled apearence upslanting palpebral fissures Small ear and folded ear
Hypoplastic ear, and folding of the ear….
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what are the had features of D. Syndrom?
Single transverse palmer crease
single flexion crease in the inside of the finger.
how is the survival of Down syndrom?
the median age of survival is about the mid Fifties.
What is the key in the process of developing Down Synderom?
nondisjunction where we have a failure in miosis I or Miosis II where the chromosomes don’t seperate and you get a monosomic or a trisomic gamete.
what causes the non-disjuction that leads to down syndrome?
the only thing that we have been able to coorilate to the occurance of D. syndrome is age of the mother. dramatic increase in risk after 35!
why would there be a large increase in the occurance of D. syndrome with an older mother
the microtubule and the cohesion proteins that are in the eggs tend to degrade over time.
how do single gene defect rates and trisomy rates differ for paternal genes?
the father’s age does not affect the rate of trisomy but it does effect the single gene mutation rate greatly!
why would you have an increased risk of a second child with down syndrome if a mother has one?
germ line mosaisism where the genes of multiple eggs have trisomy
what is the recurrence risk for the offstpring of a down syndrome mother?
50% because half will have the trisomy in the eggs
why would you see a smaller chance of down syndrome from D. syndrome mohters than predicted
75% of pregnancy is spontaniously lost
how could you have a down syndrome that can be tested in the blood and not be present and be there in other tissue?
somatic mosaicism seen in 1-5% of cases. sometimes milder expression. Tissue-specific mosiacism may occur
What could be a potential future cure of trisomey 21?
XIST inactivation. using the X inactivation gene and targeting it to the chromosome 21 and turning it into a non-transcriptional bar-body.
What is the vitality of the mitochondrial genome?
The are important in the energy production in mitochondrial.
