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BMS > Epigenetic Regulation in Health and Disease > Flashcards

Epigenetic Regulation in Health and Disease Flashcards

1
Q

Heritable changes in gene function that occurs without a change in the DNA sequence

A

Epigenetics

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2
Q

What are some common modifications to the genome?

A

DNA methylation, Histone Modification, Non-coding RNA

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3
Q

All of the epigenetic phenomena are characterized by chemical modifications to

A

DNA itself (DNA Methylation), or to Histones (The proteins around which DNA is wound)

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4
Q

In humans, DNA methylation typically occurs at the

A

Cytosine bases of DNA within CpG dinucleotides

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5
Q

Associated with the 5’-end regulatory regions of almost all housekeeping genes, as well as with half of the tissue specific genes

A

CpG rich regions (“CpG Islands”)

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6
Q

When these promoter CpG Islands are methylated, the associated genes tend to be

A

Transcriptionally inactive

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7
Q

The correct expression of many tissue-specific, germline-specific, imprinted, and X-chromosome inactivated (in females) genes, as well as that of repetitive genomic sequences, relies largely on

A

DNA Methylation

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8
Q

Play key roles in the erasure, establishment, and maintenance of DNA methylation patterns through development

A

Epigenetic modifications

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9
Q

The extent of DNA methylation changes in an orchestrated way during mammalian development, starting with a

A

Wave of demethylation during cleavage

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10
Q

However, after implantation, there is

A

Genome-wide methlyation

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11
Q

An active process that strips the male genome of methylation within hours of fertilization

A

Demethylation

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12
Q

In contrast, the maternal genome is passively demethylated during subsequent

A

Cleavage divisions

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13
Q

The extent of methylation in the genome of gastrulating embryo is high, owing to de novo methylation, but it tends to decrease in specific tissues during

A

Differentiation

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14
Q

Occurs rarely after gastrulation, but this phenomenon is seen frequently in cancer

A

De novo Methylation

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15
Q

Which enzyme removes methyl groups?

A

Demethylase (dMTase)

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16
Q

Which enzyme adds methyl groups

A

DNA methyl transferase (DNMT)

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17
Q

Replication of somatic cells results in hemimethylated DNA, which is then fully methylated by

A

DNMT

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18
Q

Negatively regulates transcriptional output

A

Transcription factor binding to methylated DNA sequence motifs

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19
Q

DNA methylation is important in

A
  1. ) Regulation of gene expression (i.e. tissue specific transcription)
  2. ) Genomic imprinting
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20
Q

An autism spectrum disorder with a monogenic origin

A

Rett Syndrome

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21
Q

A progressive neurological disorder that is one of the most common causes of mental retardation in females

A

Rett syndrome

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22
Q

What type of trait is Rett Syndrome?

A

X-linked dominant

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23
Q

Children affected by Rett syndrome have a period of apparently normal development lasting

A

6-18 months

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24
Q

What is the cause of most cases of Rett Syndrome

A

MECP2 gene mutations

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25
Q

Capable of binding specifically to methylated DNA and represses transcription from methylated gene promoters

A

MECP2

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26
Q

MECP2 is ubiquitously present, but is most abundantly expressed in the

A

Brain

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27
Q

Los of function of MeCP2 in differentiated post-mitotic neurons likely results in the inappropriate overexpression of genes with potentially damaging effects during

A

Nervous system maturation

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28
Q

The unequal expression of the maternal or paternal alleles of a gene

A

Genomic Imprinting

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29
Q

The epigenetic tags on imprinted genes usually stay put for the life of the organism, but they are reset during

A

Egg and sperm formation (Thus why they are not passed to offspring)

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30
Q

Imprinted genes play vital roles in

A
  1. ) Embryonic growth
  2. ) Neonatal behavior
  3. ) Tissue or developmental stage-specific monoallelic expression patterns
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31
Q

The SNRPN gene, producing small nuclear ribonucleoprotein N, being methylated during oogenesis but not spermatogenesis is an example of

A

Genomic imprinting

32
Q

An example of genomic imprinting because it is methylated during spermatogenesis but not oogenesis

A

The UBE3A gene

33
Q

Region that contains at least two imprinted genes, one maternally imprinted and one paternally imprinted

A

Chromosome 15

34
Q

If a child receives a chromosome 15 in which a large deletion removed the function of these genes from their father, and an (inactive) maternally imprinted gene from their mother, they will have

A

Prader-Willi Syndrome

35
Q

If a child receives the deleted chromosome 15 from their mother, and an (inactive) copy of the paternally imprinted gene from their father, they will have

A

Angelman syndrome

36
Q

Prader-Willi syndrome is indicated by

A

Mental retardation and Hyperphagia

37
Q

Angelman Syndrome is indicated by

A

Excessive laughter, seizures, and mental retardation

38
Q

In Prader-Willi syndrome, the maternal allele is imprinted by

-No SNRPN protein is expressed from the imprinted maternal chromosome 15 SNRPN allele

A

Methylation

39
Q

In Angelman syndrome, the paternal allele is imprinted by methylation resulting in

-Why a deletion in the mothers gene causes the syndrome

A

No expression of UBE3A protein by the UBE3A allele

40
Q

Histones can be reversibly modified in their amino-terminal tails, which protrude from the nucleosome core particle, by

A
  1. ) acetylation of lysine
  2. ) phosphorylation of serine
  3. ) methylation of lysine and arginine residues
  4. ) sumoylation
41
Q

The N termini of core histone proteins contain many lysine residues that impart a highly positive charge. These positively charged domains can bind tightly to
the negatively charged DNA through

A

Electrostatic Interactions

42
Q

Tight binding between DNA and histones is associated with

A

Gene inactivity

43
Q

Neutralizes the positively charged histone tails, weakening their interaction with DNA (forming euchromatin) and allowing active transcription

A

Acetylation of Histone tails

44
Q

Which enzyme acetylates histone tails?

A

Histone acetyltransferase (HATs)

45
Q

A functional RNA molecule that is transcribed from DNA but is not translated into proteins

A

non-coding RNA

-includes: miRNA, siRNA, piRNA, and IncRNA (long non-coding RNA)

46
Q

Long non-coding RNAs regulate epigenetics by

A

Chromatin remodeling, transcriptional regulation, post-transcriptional regulation, and as precursors for siRNAs

47
Q

What is an example of epigenetic regulation by long non-coding RNAs (ncRNAs)?

A

X-chromosome inactivation

48
Q

X-chromosome inactivation involves which two IncRNAs?

A
  1. ) Xist (of X-inactive specific transcript)

2. ) Tsix (its antisense transcript, a negative regulator of Xist)

49
Q

Transcribed from the X-inactivation center (XIC) of the inactive X chromosome (Xi)

A

The lncRNA Xist

50
Q

What does the Xist RNA do?

A

Covers the entire chromosome and silences gene expression through epigenetic modifications of histones and DNA (thus inactivating the X chromosome)

51
Q

Can bind to the X-inactive specific transcript (Xist) and inhibit its action, thus preventing X-inactivation

-antisense to Xist RNA

A

Tsix

52
Q

Both chromosomes will express Xist in low concentrations, but then one chromosome will start to express high levels of Tsix, which dratically reduces the concentration of Xist on that chromosome and thus, that chromosome become the

A

Active X-chromosome

53
Q

The ability of one genotype to produce more than one phenotype when exposed to different environements

A

Phenotypic plasticity

54
Q

Environmental effects (such as diet or stress) on a phenotype may involve

A

Epigenetic changes in gene function

55
Q

Changes in chromatin marks and transcriptional networks associated with sustained neuronal activity, mood disorders, and addiciton

A

Adult Neuronal plasticity and neurogenesis

56
Q

Methylation of the agouti gene results inthe agouti mRNA being made briefly during development, before the agouti gene is then silenced for the remainder of the mouses life. This leads to a

A

Healthy brown mouse

57
Q

Non-methylation of the agouti gene results in the agouti gene being continually active, producing mRNA across the mouse’s lifespan. This leads to a

A

Yellow mouse that develops obesity and diabetes during adulthood

58
Q

When a female yellow mouse (agouti gene unmethylated) was given a diet supplement during pregnancy and nursing with additional methyl groups, her offspring were

A

Mostly brown and healthy (agouti gene methylated and silenced)

59
Q

When a female yellow mouse (agouti gene unmethylated) was given no dietary supplements during pregnancy, her offspring were

A

Mostly yellow and unhealthy (agouti gene unmethylated and active)

60
Q

What are two methods to study changes in the epigenome?

A
  1. ) Bisulfite conversion of DNA

2. ) Methylation-sensitive restriction enzymes

61
Q

Converts cytidine to uridine if the citidine is NOT methylated

A

Bisulfite

62
Q

Following bisulfite conversion, the DNA strands are no longer complementary and a PCR primer is generated by a reverse transcriptase. Next we perform

A

PCR, DNA sequencing, or Methylation specific restriction enzyme digestion

63
Q

The C’s that are not methylated are converted toU’s. Then they are replicated by DNA polymerase and become

A

T’s

64
Q

We can ditect DNA methylation using methylation-sensitive restriction enzymes. The methylation incensitive restriction enzymes will

A

Cut DNA next to a methylated C

65
Q

Functionally relevant changes to the genome that do not involve a change in nucleotide sequence

A

Epigenetics

66
Q

Epigenetics are cellular and physiological traits that ARE heritable by daughter cells and not cause by changes in

A

DNA sequence

67
Q

Epigenetics describes the study of stable, usually long-term alterations in the

A

Transcriptional potential of a cell

68
Q

These covalent modifications alter how genes are expressed without altering the underlying DNA sequence

-an example of epigenetics

A
  1. ) DNA methylation

2. ) Histone modifications

69
Q

Attach to silencer regions of the DNA and remain associated with the silencer regions subsequent to DNA replication and cell division

A

Repressor proteins

70
Q

Epigenetics may last through cell divisions for the duration of a cell’s lie and may also last for multiple generations. These non-genetic factors cause the organisms genes to

A

Behave (or “express themselves”) differently

71
Q

Methylation of Cytosine can turn off

A

Gene expression

72
Q

Methylation of CpG in 98% of the genome does not matter. But methylation of the CpG stretches before transcriptional start site,

A

Inactivates transcription

73
Q

If there is an MeCP2 mutation in a boy, they will likely die as a fetus girls survive due to the fact that they have

A

Two X-Chromosomes

74
Q

Inactivation of one of the X-chromosomes is called

A

Lyonization

75
Q

Once you use a methylation-sensitive restriction enzyme technique, you can study the results with

A

Southern-blot hybridization

BMS (62 decks)

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