Chapter 16. Gene Regulation in Eukaryotes II--EpigeneticsAssignment

True or false: Epigenetic changes due to PcG complexes are transient and only present during development.

false Epigenetic changes due to the actions of PcG complexes are maintained in subsequent cell divisions.

The inactivation of an X chromosome occurs in

female mammals

Higher-order heterochromatin structure is characterized by

formation of loop domains closer contacts between nucleosomes binding of heterochromatin to the nuclear lamina

Before replication, a heterochromatic region has sites with fully methylated DNA and nucleosomes with H3K9me3 histone modifications. After DNA replication, what would be the constituents of each daughter chromatid?

half of the H3 histones with H3K9me3 modifications hemimetylated DNA

ICF syndrome and Roberts syndrome are inherited diseases associated with abnormalities in ______.

heterochromatin formation

A protein that forms a dimer in the linker region between nucleosomes carrying the modified histone H3K9me3 is

heterochromatin protein 1 (HP1)

Two nucleosomes with modified histone H3K9me3 can be brought closer together through the formation of a dimer involving

heterochromatin protein 1 (HP1)

Any assemblage of nucleosomes that assumes a reproducible confirmation in three-dimensional space represents a(n)

higher order structure

Formation of higher-order structures in heterochromatin depends upon posttranslational modifications of ________ , binding of proteins to ________, and the process of DNA __________

histones nucleosomes methylation

Polycomb group (PcG) complexes epigenetically influence development by ______ various genes.

inhibiting

In most eukaryotic cells, the inner nuclear membrane of the cell is lined by a fibrous layer of proteins called the nuclear

lamina

Condensin and CCCTC-binding factor (CTCF) are involved in forming _____ domains in heterochromatin.

loop

The methylation of hemimethylated sites is called

maintenance methylation

An RNA that does not encode a polypeptide is a(n) ______ RNA.

non-coding

Besides DNA and histone proteins, ______-________ RNAs are a critical component of chromatin.

non-coding

Genes that are expressed but do not encode polypeptides produce

non-coding RNAs

A fibrous layer of proteins lining the inner nuclear membrane of eukaryotic cells is called the

nuclear lamina

The formation of heterochromatin begins at a(n) ________ site, continues by ___________ in both directions, and stops when a(n) ___________ site is reached.

nucleation spreading barrier

Put the phases of heterochromatin formation in the correct order, placing the earliest event at the top.

nucleation spreading reaching a barrier

The basic repeating unit of chromatin is the _______, composed of ________wrapped around an octamer of ___________ proteins.

nucleosome DNA histone

Characteristics of higher-order heterochromatin structure include closer contact between ________ , formation of __________ domains and binding of heterochromatin to the nuclear ___________ .

nucleosomes loop lamina

During embryonic development, many genes within a specific cell type will undergo epigenetic changes that enable them to be ________ or cause them to be permanently ________

transcribed repressed

Which two areas of the X chromosome play a key role in X inactivation?

tsix xist

A heterochromatic region with fully methylated DNA and extensively modified histone H3 prior to DNA replication, will have ______ (the) levels of these modifications in the daughter chromatids produced after DNA replication.

1/2

Which of the following represents a higher-order structure found in chromatin?

30 nm fiber

chromatin structure in M phase through interphase in two daughter cells

Choice Constitutive and facultative heterochromatin regions retain the same pattern observed in mother cell.

chromatin structure in m phase

Choice Euchromatic regions condense into constitutive and facultative heterochromatin.

Which of the following are examples of epigenetics?

DNA methylation Covalent histone modification Localization of histone variants Chromatin remodeling

Which of the following are true regarding epigenetics?

Epigenetic changes may be transmitted to offspring Variations of gene expression are unrelated to variations in the DNA base sequence Variations are reversible from one generation to the next Epigenetic changes are transmissible from cell to cell

Identify changes that can occur during embryonic development that will lead to a pattern of differential gene expression unique to a specific cell type.

Epigenetic changes that enable specific genes to be transcribed Epigenetic changes that cause specific genes to be permanently repressed

To promote a closer association of nucleosomes, heterochromatin protein 1 (HP1) recognizes the histone modification found in

H3K9me3

When binding to chromatin, where would a dimer of heterochromatin protein 1 (HP1) be found?

In the linker region between nucleosomes

Which of the following are features associated with facultative heterochromatin?

Methylation at CpG islands located in the regulatory regions of genes Trimethylation of histone H3 at the 9th or 27th lysine Located at multiple discrete sites between the centromere and telomeres In animals, contain LINE-type repeated sequences

Which of the following is an example of epigenetic inheritance?

Methylation of DNA that occurs in an oocyte

chromatin structure in interphase

Most chromosomal regions are composed of euchromatin.

Which molecular processes will enhance the formation of higher-order structure in heterochromatin?

Posttranslational modifications of histones DNA methylation Binding of proteins to nucleosomes

Which of the following represent key functional roles for heterochromatin in eukaryotic cells?

Preventing viral proliferation Preventing movement of transposable elements Silencing genes

Idenfity the diseases that have been associated with abnormalities in heterochromatin formation.

Roberts syndrome ICF syndrome

trans-epigenetic

Trans-epigenetic mechanisms occur when a gene is activated that encodes a transcription factor that is capable of stimulating its own expression. The transcription factor may also turn on other genes.

Which of the following are features associated with constitutive heterochromatin in yeast and animal cells?

Trimethylation of a lysine at the ninth position in histone H3 Composed of many, short tandemly repeated sequences Located at telomeres and close to centromeres DNA is highly methylated on cytosines

Which two complexes are the key regulators of epigenetic changes that occur during development?

Trithorax group Polycomb group

In eukaryotic cells, which processes are prevented by heterochromatin formation?

Viral proliferation Transposable element movement Transcription

Which of the following statements regarding X inactivation are true?

When the Xist gene is inactive the X chromosome is active Expression of Tsix from both X chromosomes inhibits the expression of Xist In very early embryos, both X chromosomes are active

In mammals, females (XX) and males (XY) express genes on the X chromosome at the same levels because of

X chromosome inactivation

Which of the following statements regarding X chromosome inactivation is true?

X chromosome inactivation occurs during embryogenesis in females.

The X-inactivation center consists of which two genes?

Xist Tsix

What happens when pluripotency factors stimulate the expression of Tsix?

Xist is inhibited.

Trithorax group (TrxG) complexes epigenetically influence development by ______ various genes.

activating

Epigenetic changes due to the actions of PcG complexes

are maintained in subsequent cell divisions

An area of the chromosome that protects a euchromatic region from spreading of adjacent heterochromatin is called a(n)

barrier

Which component can prevent heterochromatin spreading into an adjacent euchromatic region of the chromosome?

barrier

Lamina-associated domains (LADs) are regions of ______ found in close contact with the nuclear lamina in eukaryotic cells.

chromosomes

Genomic imprinting and X-chromosome inactivation are examples of ______ mechanisms that occur during development.

cis-epigenetic

If an epigenetic change is maintained only at a given site and does not affect the expression of a gene elsewhere in the nucleus, it is a ______ mechanism.

cis-epigenetic

Which type of epigenetic mechanism is shown in the image?

cis-epigenetic mechanism If an epigenetic change is maintained only at a given site and does not affect the expression of a gene elsewhere in the nucleus it is a cis-epigenetic mechanism.

Identify proteins involved in forming loop domains in heterochromatin.

condensin CCCTC-binding protein

Regions of the chromatin containing numerous, short, tandemly repeated sequences that are located near the centromeres and at the telomeres of eukaryotic chromosomes are called ______ heterochromatin.

constitutive

Regions of heterochromatin that are seen in the same location in all cell types are called

constitutive heterochromatin

The methylation of a previously unmethylated site is called

de novo methylation

A series of genetically programmed stages that begins with sperm and eggs that fuse to become an embryo that will eventually change into an adult is called

development

In multicellular species, ________ involves a series of genetically programmed stages in which a fertilized egg becomes an embryo and eventually changes into an adult.

development

Chromosomal regions that are in close contact with the nuclear lamina are called lamina-associated

domains (LADs)

X-chromosome inactivation is an epigenetic event that occurs during

embryogenesis

The inactivation of an X chromosome is a

epigenetic event

DNA methylation, chromatin remodeling, covalent histone modification, and localization of histone variants are all examples of molecular mechanisms that are involved in

epigenetics

The variation of gene expression that is not related to the variation of the DNA, is transmissible, and is reversible is described as

epigentics epimutations

Heterochromatic regions found at multiple discrete sites located between the centromeres and telomeres, and which contain methylated DNA at CpG islands in regulatory regions, are called ______ heterochromatin.

facultative

Regions of heterochromatin that vary among different cell types are called _________-heterochromatin.

facultative

During cell division, from M phase in the mother cell to interphase in the resulting two daughter cells, a chromosome will usually retain the same pattern of ________ and ___________ heterochromatin that was found in the mother cell.

facultative constitutive

True or false: Because epigenetics refers to heritable changes in gene expression, all epigenetic changes are examples of transgenerational epigenetic inheritance.

false