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M2M Unit II > Genetic Imprinting > Flashcards

Genetic Imprinting Flashcards

1
Q

Prader-Willi syndrome is characterized by _____.

A

obesity, excessive and indiscriminate eating, short stature, small hands and feet, hypogonadism, and intellectual disabilities

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2
Q

imprinting

A

genes that are functionally hemizygous because one parental allele is silenced; a sex-dependent epigenetic modulation

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3
Q

The imprinted genes encode both ________ and ________.

A

proteins and non-coding RNAs

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3
Q

The inherited form of _________ is exclusively inherited from mothers

A

Angelman syndrome

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4
Q

DNA methylation is maintained in __________.

A

somatic cells after fertilization

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4
Q

uniparental disomy

A

inheriting two copies of a chromosome from one parent, or no copies from one parent

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4
Q

Uniparental disomy most commonly occurs when a trisomic conceptus loses one of its extra chromosomes due to _______.

A

mitotic nondisjunction in early gestation

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6
Q

What is one sex-dependent epigenetic modulation mechanism?

A

imprinting

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6
Q

Angleman Syndrome patients have a deletion of approximately the same region of chromosome 15 as Prader-Willi patients but on the _____ derived homolog.

A

maternally

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7
Q

_________ is characterized by obesity, excessive and indiscriminate eating, short stature, small hands and feet, hypogonadism, and intellectual disabilities.

A

Prader-Willi syndrome

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7
Q

The 15q11-q13 region contains ____ paternally expressed genes.

A

three

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7
Q

Uniparental disomy most commonly occurs when a trisomic conceptus loses _______ due to mitotic nondisjunction in early gestation.

A

one of its extra chromosomes

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7
Q

Demethylation could result from the inhibition of _____, or indirectly through the inactivation of chromatin-remodeling proteins.

A

the maintenance methyltransferase, DNMT1

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9
Q

How many human genes are imprinted?

A

about 1%

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11
Q

How does CpG methylation affect gene expression?

A

chromatin structure is compacted to repress transcription

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11
Q

DNA methylation is established _________.

A

in the gamete

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13
Q

DNA methylation is the epigenetic mark that mediates __________.

A

genetic imprinting

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14
Q

Which chromosome is mutated to result in Prader-Willi and Angleman Syndrome?

A

15

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15
Q

To accomplish such epigenetic inheritance, parental patterns of methylation are erased in ______ as part of overall genomic reprogramming.

A

primordial germ cells

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16
Q

The chromosomal sorting error in uniparental disomy “rescues” the developing pregnancy from spontaneous abortion but may result in an abnormal phenotype if both remaining homologs are derived from _______.

A

the same parent

16
Q

15q11-13 locus relevance

A

uniparental disomy - Prader-Willi and Angelman Syndrom

17
Q

________ could result from the inhibition of the maintenance methyltransferase, DNMT1, or indirectly through the inactivation of chromatin-remodeling proteins.

A

Demethylation

18
Q

epigenetic

A

mitotically and meiotically inheritable variation in gene expression that is not caused by a change in DNA sequence

18
Q

In addition to parent of origin effects due to deletions, genetic imprinting also leads to abnormal phenotypes in association with ______.

A

uniparental disomy

20
Q

Imprinted gene clusters contain both _____ and ______ imprinted genes.

A

maternally and paternally

21
Q

In uniparental disomy, if both remaining 15 homologs are maternal in origin, both carry maternally repressed loci, but normal development is dependent on expression of genes at the missing _______.

A

paternal locus

21
Q

Which trisomies can survive to live birth?

A

13, 18, and 21

22
Q

DNA methylation is __________ so that it can be reset during gametogenesis.

A

reversible

23
Q

Erasure and resetting of the imprint appears to occur at _______.

A

imprinting centers (IC)

24
Q

What would happen if methylation marks are not erased during gametogenesis?

A

total silencing of both copies of the gene would occur at a very high rate

26
Q

______ is characterized by an unusual facial appearance, short stature, severe intellectual disabilities, spasticity, and seizures.

A

Angelman syndrome

28
Q

What enzyme methylates a histone?

A

histone methyltransferase

29
Q

Where is the promoter region normally found?

A

near the centromere

31
Q

New, sex-dependent imprints (patterns of methylation) are initiated during ___________.

A

gametogenesis

32
Q

In 70% of Prader-Willi patients, the syndrome is the result of a cytogenetically observable _____ involving the long arm of chromosome 15 (15q11-q13), occurring on the chromosome 15 homolog inherited from the patient’s _____.

A

deletion; father

33
Q

What recognizes hemi-methylated DNA strands and methylates the newly synthesized strand?

A

maintenance methyltransferase

34
Q

What is the job of a maintenance methyltransferase?

A

recognize hemi-methylated DNA strands and methylate the newly synthesized strand

35
Q

___________ is the epigenetic mark that mediates genetic imprinting.

A

DNA methylation

37
Q

Which two syndromes are caused by maintenance of methylation marks during gametogenesis?

A

1) Prader-Willi 2) Angleman syndrome

38
Q

Imprinting centers (IC) contain non-coding DNA sequences that bind imprinter _____ and recruit DNA methyltransferase (DNMT) complexes that methylate CpG islands located near the IC on the same chromosome (cis).

A

RNA transcripts (BD transcripts)

39
Q

__________ is when genes are functionally hemizygous because one parental allele is silenced.

A

Imprinting

41
Q

________ most commonly occurs when a trisomic conceptus loses one of its extra chromosomes due to mitotic nondisjunction in early gestation.

A

Uniparental disomy

42
Q

Demethylation could result from the inhibition of the maintenance methyltransferase, DNMT1, or indirectly through the _______.

A

inactivation of chromatin-remodeling proteins

43
Q

Two epigenetic mechanisms?

A

1) reversible, post-translational modifications of histones 2) DNA methylation

44
Q

Mutations at ______ are heritable lesions that can generate the same abnormal phenotypes as deletions or uniparental disomies.

A

imprinting centers

46
Q

What is the molecular basis for genetic imprinting?

A

Methylation of cytosine residues in CpG residues of promoter regions

47
Q

Once sex-specific patterns of methylation are established during gametogenesis, the patterns are retained in somatic cells by _______.

A

maintenance methylation

48
Q

15q11-q13 region genes encode proteins for ______.

A

placental development, fetal growth

M2M Unit II (21 decks)

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