Molecular Bio (Exam 3): Epigenetics

Epigenetics are heritable changes in gene activity without any changes in what?

DNA sequence.

Epigenetic regulation involves what two mechanisms?

DNA methylation and histone modifications.

Self-perpetuating structures are often ________ by forming heterochromatic regions.

repressive.

What happens to active genes inserted within or near heterochromatin?

inactivated.

What is the process of heterochromatin being nucleated at a certain site?

nucleation.

Heterochromatin inactive structure propagation is due to what?

epigenetic effect.

The closer a gene is to heterochromatin, the higher its chance to?

get inactivated.

Heterochromatin propagates from a what?

nucleation event.

The length of the ________ region can vary from cell to cell.

inactive.

Inactivation of genes variation in cells causes ________ ________ ________ (PEV).

position effect variegation.

Heterochromatin ________ may be inherited by insulators, active promoters, and depletion of a protein factor.

propagation.

The probability that a gene will be inactivated depends on its distance from what region?

heterochromatin.

The effect of telomeric silencing in yeast is analogous to what?

PEV.

In ________ silencing in yeast, genes translocated to a telomeric location show variable loss of activity.

telomeric.

In telomeric silencing in yeast, ________ binds telomere and recruits HP1 for nucleation.

Rap1.

In telomeric silencing in yeast, Rap1 binds telomere and recruits ________ for nucleation.

HP1.

In telomeric silencing in yeast, HP1 induces ________ ________ resulting in recruitment of more HP1 proteins for propagation.

chromatin modification.

In telomeric silencing, ________ induces chromatin modification, resulting in recruitment of more ________ proteins for propagation.

HP1.

Heterochromatin depends on interactions with what?

histones.

What is the key protein in forming mammalian heterochromatin and acts by binding to methylated histone H3?

HP1.

HP1 forms mammalian heterochromatin by binding to what?

methylated histone H3.

HP1 contains a ________ that binds to H3K9me3.

chromodomain.

HP1 contains a chromodomain and binds to what?

H3K9me3.

Active chromatin is deacetylated and then methylated by what?

HMTs.

H3K9me3 recruits what?

HP1.

HP1 recruits SUV39H1 and propagates H3K9 ________.

methylation.

More MP1 is recruited and chromatin is ________.

inactivated.

X chromosomes undergo ________ changes.

global.

Mechanisms employed to equalize the level of expression of X-linked genes in the two sexes is done by ________ ________.

dosage compensation.

The common feature of dosage compensation is that the entire ________ is the target for regulation.

chromosome.

Permanently non-expressed sequences, usually satellite DNA, are present in ________ heterochromatin.

constitutive.

Sequences that also exist in active copies are present in ________ heterochromatin.

facultative.

One X chromosome in female mammals are considered ________ heterochromatin.

facultative.

The cis-acting element that is necessary and sufficient for X inactiation.

Xic (X-inactivation center).

The X inactive specific transcript that is required for X inactivation.

Xist.

Xist is a ________ ________ and very unstable.

noncoding RNA.

RNA instability is not due to its structure but rather what?

degradation enzymes.

Xist is regulated in a ________ manner by Tsix, which is anti-sense to Xist.

negative.

Tsix forms double strand with Xist and further ________ Xist.

destabilizes.

Accumulation of ________ on the future inactive X chromosome leads to the recruitment of Polycomb repressor complexes, which causes histone modifications.

Xist.

An inactive X-specific histone variant that is incorporated during X chromosome inactivation.

macroH2A.

When macroH2A is incorporated, most ________ DNAs are methylated.

promoter.

The heterochromatic state of inactive X is ________.

stable.

Xist is not required for the maintenance of ________ state.

inactive.

__% of genes are still transcribed from inactive X.

5.

In Drosophila, a ribonucleoprotein complex, ________, is found only in males and localized on the X chromosome.

MSL.

In Drosophila, the MSL complex is only found in ________ and is localized on the X chromosome.

males.

MSL contains 2 ________ ________ and a HAT.

non-coding RNAs.

The 2 noncoding RNAs in MSL complex is important for its localization to what?

X chromosome.

The HAT in MSL complex is for H4K16 ________ throughout the male X.

acetylation.

Transcription of genes on the male X chromosome is two-fold ________.

increased.

In ________, females use mechanisms to globally condense the 2 X chromosomes in reduce expression of each by half compared to the male X chromosome.

C elegans.

Demethylation at the ___’ end of the gene is necessary for transcription in higher eukaryotes.

5’.

Methylation of promoter in higher eukaryotes is correlated with transcriptional ________.

silencing.

The major methylation site in higher eukaryotes is what?

CpG island.

CpG islands are frequently found in ________ regions.

promoter.

Methylation may inhibit activators from binding or may recruit ________.

repressors.

De novo methyltransferases methylate unmethylated ________.

CpG.

What 2 proteins are de novo methyltransferases?

Dnmt3A and Dnmt3B.

Hemimethylated sites are converted to fully methylated sites by a ________ methyltransferase.

maintenance.

What protein is a maintenance methyltransferase?

Dnmt1.

Dnmt1 ________ results in embryonic lethality in mice.

knockout.

In humans, ________ mutation causes ICF (immunodeficiency centromere instability, facial anomalies).

Dnmt3B.

________ mutation is associated with Rett syndrome.

MeCP2.

DNA methylation and heterochromatic state are mutually ________.

reinforcing.

DNA methylation promotes ________ ________ and vise versa.

histone methylation.

Histone methylation promotes ________ ________ and vise versa.

DNA methylation.

Dnmt1 augments HP1 binding and recruits H3K9 methyltransferase, which is ________ feedback.

positive.

Imprinting is epigenetic changes during ________, resulting in differential behavior of genes/alleles inherited from each parent.

gametogenesis.

Imprinting is caused by DNA ________, therefore imprinted genes/alleles are inactive.

methylation.

For imprinting, the existing pattern is erased by genome-wide ________.

demethylation.

For imprinting, the sex-specific methylation is imposed during ________.

meiosis.

Imprinted genes occur in clusters and ay depend on local control site where what occurs?

de novo methylation.

Imprinted genes are controlled by ________of cis-acting sites called DMDs or ICRs.

methylation.

Imprinted genes are controlled by methylation of DMDs or ICRs, which are what?

cis-acting sites.

Deletion of cis-acting sites (DMDs or ICRs) removes ________, and the target loci behave the same in both maternal/paternal genomes.

imprinting.

Deletion of what sites removes imprinting?

cis-acting sites (DMDs or ICRs).

Igf2 and H19 on mouse chromosome 7 are imprinted and regulated by the same ________.

enhancer.

Methylation of ICR causes opposite effect on H19 and Igf2 because ICR also functions as an ________, whose function is regulated by methylation.

insulator.

H19 is expressed from ________ allele.

maternal.

Igf2 is expressed from ________ allele.

paternal.

ICR functions as an insulator whose function is regulated by ________.

methylation.