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Flashcards in 3 Non-Mendelian Deck (19):

what is anticipation? what type of molecular conditions is this seen in?

the increase in severity or earlier onset of a phenotype in successive generations
-trinucleotide repeats


myotonic dystrophy
-what classification of genetic disease?
-what genetic fundamental does it show?
-spectrum of severity

-trinucleotide repeats
-Mild (cataracts, myotonia, normal life span), classic (muscle weakness, wasting, myotonia, cataracts), congenital ( severe hypotonia, respiratory insufficiency, early death)


Fragile X syndrom
-what classification of genetic disease?
-demonstrates what genetic principle?
-precise genetic cause?
-physical characteristics

-trinucleotide expansion (and X linked)
-anticipation: bu not classic - severity of intellectual ability does not increase with repeat size
-CGG repeat expansion in FMR1 on the X chromosome
-most common inherited disability, lang face, large ears


what are the characteristics of premutation fragile x carriers?

-women: risk of premature ovarian insufficiency
-men: risk of tremor and ataxia syndrome - these are late onset with cognitive decline and brain atrophy


what are the two general types of mosaicism?



what is somatic mosaicism caused by?

post-zygotic mutation
-disease severity variable


give an example of a disease that is only seen in mosaic form?

pallister killian syndrome


Pallister Killian Syndrome:
-molecular cause

-mosaic tetrasomy 12p
-low muscle tone
-characteristic faces, high arched palate, hypopigmentation, supernumerary nipples


in gonadal mosaicism, is the person affected by the change?

-no, only found in the gametes


in a pedigree, how can you see gonadal mosaicism? can you test for this?

when at lest two offspring have an autosomal dominant disorder with no other family history
-no, because there is no way to tell what percentage of sperm cells have the mutation


what is imprinting?

epigenetic modifications made to the DNA in order to preferentially express certain genes from a certain chromosome (ie either the inheritted from dad or mom)


what is impritning reset?

-this occurs during spermatogenesis so that every chromosome incorporated into a gamete produced by an individual is specifically imprinted for their gender


what does the placenta and fetus look like when there are two paternal and one maternal chromosome present? (diandric triploidy)

-normal to slightly small fetus, lasrge cystic placenta


what does the placenta and fetus look like when there are two maternal chormosome and one paternal present?

-small fetus and small placenta


10% of Russell Silver syndrome are attributed to what?

maternal UPD of chromosome 7


what is heterodisomy?

when there is nondysjunction in meiosis 1 and two homologous (nonidentical) chromosomes get passed on from one parent to the child


what is isodisomy?

when there is nondysjunction in meiosis 2 and two identical copies of the same chromosome get passed on from a parent


Prader wili syndrome
-molecular cause

-lack of expression from genes in the critical region of a PATERNAL allele
-hyperphagia, hypotonia, intellectual disability


angelmans syndrome
-molecular cause

-lack of expression of genes in a critical region of a Maternal region