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GENE30005 Human and Medical Genetics > Epigenetics (14,15) > Flashcards

Epigenetics (14,15) Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

Which enzyme is not involved in epigenetics?

a. Writers which add histone modifications
b. Extenders that duplicate histone modifications
c. Erasers that remove histone modifications
d. Readers that bind histone modifications

A

b. Extenders that duplicate histone modifications

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2
Q

What is not an epigenetic mechanism?

a. RNA splicing
b. Histone modification
c. LncRNA
d. DNA methylation

A

a. RNA splicing

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3
Q

What is a feature of DNA methylation?

a. Guanine residues are methylated
b. DNA is activated
c. Changes are heritable
d. Chromatin is not affected

A

c. Changes are heritable

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4
Q

What is involved in DNA packing and histone modification?

a. Changes to histones cannot be inherited
b. A human cell has 3cm of DNA (metre)
c. Nucleosomes come together to form a histone
d. Modifications alter DNA accessibility

A

d. Modifications alter DNA accessibility

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5
Q

What is a feature of long non coding RNA?

a. They bind chromatin modifying proteins
b. They interact with the genome in a non-specific manner
c. They cannot influence mRNA splicing or stability
d. PRC2 is encoded for by a lncRNA

A

a. They bind chromatin modifying proteins

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6
Q

What is a feature of an epigenetic phenomenon?

a. X inactivation is found in marsupials only
b. Genomic imprinting is localised gene silencing on autosomes
c. Genomic imprinting is conserved in all mammals
d. X inactivation allows gene expression to be higher in males than females

A

b. Genomic imprinting is localised gene silencing on autosomes

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7
Q

What is a not a feature of XIST?

a. It encodes a 17kb non coding RNA
b. It is the only gene expressed on the X chromosome to be inactivated
c. It coats the X chromosome that will remain active
d. It is cis acting and recruits epigenetic machinery

A

c. It coats the X chromosome that will remain active

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8
Q

What happens if the A loop of XIST is deleted?

a. PRC2 and PRC1 are overexpressed
b. PRC2 cannot bind and carry out methylation
c. H3K27 will be trimethylated
d. The gene state will become inactive

A

b. PRC2 cannot bind and carry out methylation

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9
Q

What is a feature of TSIX?

a. It causes the promoter of XIST to be methylated
b. It is downregulated on the active X chromosome
c. It is expressed on both X chromosomes
d. It is upregulated on the inactive X chromosome

A

a. It causes the promoter of XIST to be methylated

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10
Q

What is a feature of genomic imprinting?

a. About 100 genes are imprinted and therefore dizygotic
b. It can only result from histone modification
c. Imprints are reproduced during cell divisions and erased in the germline
d. Inherited maternal and paternal genomes are functionally equivalent

A

c. Imprints are reproduced during cell divisions and erased in the germline

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11
Q

In terms of genomic imprinting, what is the result of a two paternal genome?

a. A large foetus and large placenta
b. A small foetus and large placenta
c. A large foetus and small placenta
d. A small foetus and small placenta

A

b. A small foetus and large placenta

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12
Q

• DNA methylation depends on a cytosine residue preceding a guanine residue.

A

T

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13
Q

• Many epigenetic diseases are due to mutations in genes affecting methyltransferases and Demethylases.

A

T

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14
Q

• A foetus can still be viable with two active X chromosomes.

A

F

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15
Q

• The barr body is distinct as a dense heterochromatin structure during interphase in XX females.

A

T

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16
Q

• XIST is one of 3 genes expressed on the inactivated X chromosome.

A

F

17
Q

• TSIX is expressed from both X chromosomes.

A

F (only the active)

18
Q

• XACT is an LncRNA that coats the active X chromosome in human pluripotent cells.

A

T

19
Q

• Marsupials express XIST and XACT.

A

F (neither)

20
Q

What is not a feature of the H19 imprinting cluster?

a. H19 is a lncRNA
b. H19 is only expressed on the maternal chromosome
c. IGF2 is expressed on the maternal and paternal chromosome
d. IGF2 and H19 have separate enhancers upstream of H19

A

c. IGF2 is expressed on the maternal and paternal chromosome

21
Q

What is the role of CTCF and the DMR?

a. The DMR binds regions of methylated DNA to block transcription
b. CTCF binds to the DMR on the maternal chromosome to block IGF2 expression
c. The paternal DMR is methylated to encourage CTCF binding
d. CTCF binds to un-methylated chromatin on the maternal and paternal chromosome

A

b. CTCF binds to the DMR on the maternal chromosome to block IGF2 expression

22
Q

How can IGF2 imprinting be linked to disease?

a. When the maternal and paternal chromosomes are methylated at the ICR, Wilms tumours can form
b. When neither chromosome is methylated at the ICR, there is excess cell proliferation
c. When the maternal chromosome is methylated and the paternal chromosome is un-methylated, MET is demonstrated
d. When the maternal and paternal chromosomes are methylated at the ICR there is a loss of cellular adhesion

A

a. When the maternal and paternal chromosomes are methylated at the ICR, Wilms tumours can form

23
Q

Which statement is correct in regards to SNRPN imprinting?

a. The most common origin of angelman syndrome is through imprinting mutation
b. A deletion in the paternal chromosome results in a silenced PWS region and Prader Willi syndrome
c. Deletion mutations are rarely the cause of Angelman and Prader Willi syndrome
d. A deletion in the maternal chromosome results in an upregulated AS region and Prader Willi syndrome

A

b. A deletion in the paternal chromosome results in a silenced PWS region and Prader Willi syndrome

24
Q

What is not a function of a lncRNA?

a. Protein synthesis shown by rRNA
b. X inactivation shown by XIST RNA
c. Epigenetic modification and chromatin remodelling
d. Splicesome formation shown by snRNA

A

d. Splicesome formation shown by snRNA (small non coding RNA)

25
Q

What is a feature of hypospadias?

a. It can be seen in sons of women exposed to DES
b. It is now rarely seen in Australian births
c. The increase is occurring slower than genetic changes
d. In utero exposure to estrogenic chemicals and decrease the chance of the disease

A

a. It can be seen in sons of women exposed to DES

26
Q

What is involved in trans-generational inheritance?

a. It can be proven by observing defects in the F2 and parents only
b. Reprogramming of the germ line occurs in the gonads
c. Only the parent generation receives direct exposure
d. The use of DES in the 1930s has had no trans generational consequences

A

b. Reprogramming of the germ line occurs in the gonads

27
Q

• Imprint genes are often found in clusters.

A

T

28
Q

• Snrpn is active only on the maternal chromosome.

A

F

29
Q

• H19 recruits MBD1 which modifies chromatin on the paternal chromosome to silence IGF2.

A

F

30
Q

• A H3K4me3 modification is associated with active promoters and a H3K27me3 modification is associated with inactive chromatin.

A

T

31
Q

• 30% on lncRNAs in ESCs are for chromatin modification and 23% interact with PRC2.

A

T

32
Q

• In agouti mice, higher levels of methylation can result in a more yellow coat.

A

F (more meth = brown)

33
Q

• Multiple generations can be affected by unfavourable in utero conditions, not just the F2.

A

T

GENE30005 Human and Medical Genetics (13 decks)

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