3 Non-Mendelian

Question 1

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

Answer 1

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

Question 2

myotonic dystrophy

• what classification of genetic disease?
• what genetic fundamental does it show?
• spectrum of severity

Answer 2

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

Question 3

Fragile X syndrom

• what classification of genetic disease?
• demonstrates what genetic principle?
• precise genetic cause?
• physical characteristics

Answer 3

• 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

Question 4

what are the characteristics of premutation fragile x carriers?

Answer 4

• women: risk of premature ovarian insufficiency

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

Question 5

what are the two general types of mosaicism?

Answer 5

• somatic

- gonadal

Question 6

what is somatic mosaicism caused by?

Answer 6

post-zygotic mutation

-disease severity variable

Question 7

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

Answer 7

pallister killian syndrome

Question 8

Pallister Killian Syndrome:

• molecular cause
• features

Answer 8

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

Question 9

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

Answer 9

-no, only found in the gametes

Question 10

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

Answer 10

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

Question 11

what is imprinting?

Answer 11

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)

Question 12

what is impritning reset?

Answer 12

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

Question 13

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

Answer 13

-normal to slightly small fetus, lasrge cystic placenta

Question 14

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

Answer 14

-small fetus and small placenta

Question 15

10% of Russell Silver syndrome are attributed to what?

Answer 15

maternal UPD of chromosome 7

Question 16

what is heterodisomy?

Answer 16

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

Question 17

what is isodisomy?

Answer 17

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

Question 18

Prader wili syndrome

• molecular cause
• symptoms

Answer 18

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

Question 19

angelmans syndrome

-molecular cause

Answer 19

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