Genetic Imprinting Flashcards Preview

M2M Genetics > Genetic Imprinting > Flashcards

Flashcards in Genetic Imprinting Deck (24)
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1
Q

What is epidemiology?

A

the study of mitotically and or meiotically heritable changes in gene function that cannot be explained by changes in DNA sequences

2
Q

how does epigenetics relate to imprinting?

A

gene silencing through methylation patterns on DNA

3
Q

what is genetic imprinting?

A

autosomal genes are inherited in a silenced state from 1 parent and a activated state from the other parent

4
Q

what is hemizygous?

A

only one gene is active or correctly expressed

5
Q

when does imprinting take place?

A

during gametogenesis before fertilization

6
Q

how is DNA methylation involved in gene silencing?

A

methylation of promoters can cause the gene to be silenced or by recruiting factors that repress transcription

7
Q

how is DNA methylation involved in gene activation?

A

mechanism poorly understood, but current model states may prevent binding of transcriptional repressor

8
Q

True or False

Imprinting must be reversible

A

True

must be wiped clean when gametogenesis occurs to pass da genes

9
Q

what are the characteristics of imprinted genes?

A
  1. clustered together
  2. contain maternal and paternal imprinted genes
  3. encode both proteins and non-coding RNA’s
10
Q

what are the essential characteristics of the epigenetic mark?

A
  1. modification must be established in gametes

2. allele modifications must be stably maintained after fertilization

11
Q

what causes prader-willi and angelman syndrome?

A

deletion on long arm of chromosome 15

del 15 q11-q13

12
Q

how does prader-willi syndrome come about?

A

deletion on the paternal chromosome with deactivated maternal chromosome

13
Q

what is the presentation of patients with prader-willi syndrome?

A
  • obesity
  • excessive and indiscriminate eating
  • short stature
  • small hands and feet
  • hypogonadism
  • mental retardation
14
Q

how does angelman syndrome come about?

A

deletion of maternal chromosome with deactivated paternal chromosome

15
Q

what is the phenotype of angelman syndrome?

A
  • unusual facial appearance
  • short stature
  • sever mental retardation
  • spasticity
  • seizures
16
Q

what is the main way that you can discriminate phenotypically between angelman syndrome and prader-willi syndrome?

A

obesity is only present in prader-willi syndrome

17
Q

what is uniparental disomy?

A

when child receives 2 paternal or maternal chromosome rather than 1 of each

18
Q

what is the most common uniparental disomy?

A

trisomy 15 from maternal non-disjunction leading to 2 maternal and 1 paternal

19
Q

if trisomy 15 is not compatible with life, how does a uniparetnal disomy occur?

A

non-disjunction early in gestation

20
Q

how does demethylation of imprinted genes occur?

A

inhibition of maintenance methyltransferase (DNMT1, or through inactivation of chromatin-remodeling proteins

21
Q

where does erasure and resetting of imprinting occur?

A

at imprinting centers

22
Q

what does an imprinting center contain?

A

non-coding DNA sequences that bind imprinter RNA transcripts and recruit DNA methyltransferase (DNMT)

23
Q

what is the function of DNA methyltransferases (DNMT)

A

complexes that methylate CpG islands located near IC on same chromosome

24
Q

how is imprinting maintained after cell division of somatic cells?

A

maintenance methylation, have to methylate newly synthesized daughter strand