Genetic Imprinting (Megee L3) Flashcards Preview

Ann's M2M - Weeks 3, 4 > Genetic Imprinting (Megee L3) > Flashcards

Flashcards in Genetic Imprinting (Megee L3) Deck (40)
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30

What is Uniparental Disomy?

Both autosomes are inherited from one parent.

31

What would be a likely cause of uniparental disomy?

1. Nondisjunction during meiosis I, resulting in a diploid gamete from parent 1.
2. Upon fertilization, zygote is now trisomic
3. If mitotic nondisjunction then results in the loss of the chromosome from parent 2, leaving only parent 1's two copies, the conceptus now has two copies of the chromosome, but both are from parent 1.

32

Nondisjunction is more likely during maternal or paternal meiosis?

maternal

33

Whys is uniparental disomy a more common cause of Prader-Willi syndrome than of angelman syndrome?

Meiotic nondisjunction is more likely in the maternal gameteogenesis.

It is thus more likely that Mom contributes two transcriptionally silent PW genes. If Dad's chromosome 15 is not present, PW syndrome results.

34

What percent of PW syndrome cases are due to uniparental disomy and which parent do the two chromosome 15's come from?

25%
both maternal chromosome 15's (which are trxn'ly silent for SNORD116)

35

What percent of Angelman syndrome cases are due to uniparental disomy and which parent do the two chromosome 15's come from?

s (which are trxnly silenced for UBE3A)

36

What percentage of the genes in the human genome are subject to genetic imprinting?

1%

37

Histone 3, Lysine 4 (H3K4) is a(n) ____________ methylation.

activating

38

What region on the DNA initiates the imprinting process and what do we know about the mechanism of action?

Imprinting centers - DNA elements located within imprinted genes are the governing elements of imprinting.

We know very little about their mechanism of action...

39

What is Albright Hereditary Osteodystrophy?

AHO is a fully penetrant autosomal dominant trait
obesity, short stature, subcutaneous calcifications, brachydactyly (4th, 5th metacarpals)

Often, but not always, associated with PHP (pseudohypoparathyroidism)
GNAS gene is defective
*** is an example of maternal / paternal imprinting only in certain tissues

(see p. 137-139 from reading list in Megee's L3)