genetics chapter 17

Transcription factors that affect the ability of RNA polymerase to begin the transcription process may work by ______.

- regulating the binding of the transcriptional complex to the core promoter - controlling the switch from the initiation to the elongation stage of transcription

What is the size of the nucleosome-free region found at the core promoter of active genes?

150 bp

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

30-nm fiber

In eukaryotes, DNA methyltransferase is an enzyme that attaches a methyl group to the position of the base.

5 Cytosine

In somatic cells of female mammals, one of the two X chromosomes becomes a condensed body, where the genes are inactivated.

Barr

The basic repeating unit of chromatin is the , composed of wrapped around an octamer of proteins.

Blank 1: nucleosome Blank 2: DNA Blank 3: histone

5-methylcytosine is formed by ______.

DNA methyltransferase

Variants have been identified for which of the following histones?

H1 H3 H2A H2B

How do transcription factors contribute to epigenetic modification?

Transcription factors recruit chromatin modifying proteins, such as DNA methyltransferase.

Transcription factors called pluripotency factors stimulate the expression of ______, which inhibits the expression of ______ to keep both X chromosomes in an active state during early embryogenesis.

Tsix, Xist

Many epigenetic modifications are programmed changes that occur during developmental stages such as or .

gametogenesi embryogenesis

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

lamina

Mice that are homozygous for the loss-of-function mutation in the Agouti gene will have black fur because ______.

pheomelanin is not produced

Prior to X-chromosome inactivation, factors stimulate the expression of Tsix to maintain the activity of both X chromosomes.

pluripotency

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

preventing movement of transposable elements preventing viral proliferation silencing genes

Female honeybee larvae bathed in royal jelly throughout their larval development and fed it into adulthood become bees.

queen

Once inside the cell, the glucocorticoid hormone binds to a glucocorticoid ______, releasing it from a protein known as HSP90.

receptor

The regulatory transcription factors that respond to glucocorticoid hormones are called glucocorticoid

receptor

The phenomenon where gene expression is controlled so that genes can be expressed at high or low levels is called gene .

regulation

X-chromosome inactivation occurs in ______ cells of ______ mammals.

somatic; female

Excess iron in animal cells is stored within a hollow, spherical protein known as .

Ferritin

Nucleosomes containing the histone variant , which are usually found at the +1 nucleosome, are thought to be more easily removed from the DNA than those containing the standard histone .

H2A.Z H2A

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

H3K9me3

DNA methylation is the attachment of methyl groups to DNA.

covalent

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

heterochromatin protein 1 (HP1)

The covalent attachment of a -CH3 group to DNA is known as DNA ______.

methylation

Which of these are true regarding epigenetics?

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

Variation of gene expression that is transmissible and reversible but not related to the variation in the DNA is called

Epigenetics

The two genes Xist and Tsix play a role in -chromosome .

X inactivation

X-chromosome inactivation is an epigenetic event that occurs during ______.

embryogenesis

The inactivation of an X chromosome is a(n) ______ event.

epigenetic

An enhancer is a DNA element that is bound by a regulatory transcription factor, which leads to ______.

up regulation

The function of regulatory transcription factors must be modulated to ensure that genes are turned on ______.

under the appropriate environmental conditions in the correct cell type at the proper time

Most histone genes encode standard histone proteins, but some have accumulated mutations that change the amino acid sequence of the histone proteins. These proteins are called histone .

variants

Which of the following represents a programmed epigenetic change that occurs during development?

X-chromosome inactivation in female mammals

Lysine residues on core histone proteins can be acetylated by enzymes called histone

acetyltransferases

TFIID binds to the box and helps recruit RNA polymerase II to the core .

tata promoter

Place these steps in a simplified model for transcriptional activation of a eukaryotic gene in order, with the first step at the top.

1. Binding of an activator to an enhancer in the NFR2. Recruitment of a chromatin-remodeling complex and a histone-modifying enzyme3. Recruitment of general transcription factors and RNA Pol II to the core promoter, allowing the formation of a preinitiation complex4. Eviction or destabilization of histone octamers, allowing RNA pol II to pass, and elongation to occur.

1. Interphase 2.M phase 3. M phase through interphase in two daughter cells

1. Most chromosomal regions are composed of euchromatin. 2. Euchromatic regions condense into constitutive and facultative heterochromatin. 3. Constitutive and facultative heterochromatin regions retain the same pattern observed in mother cell.

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

Blank 1: histones or histone Blank 2: nucleosomes or nucleosome Blank 3: methylation

The Igf2 gene in mammals is only expressed from the paternal chromosome. This is due to different patterns of DNA methylation during oogenesis and spermatogenesis. Methylation can occur at two different sites: the region (ICR), and the region (DMR).

Blank 1: imprinting Blank 2: control Blank 3: differentially Blank 4: methylated

This figure shows the region of a chromosome that contains the Igf2 and H19 genes in mammals. ICR refers to region, while DMR stands for region.

Blank 1: imprinting Blank 2: control Blank 3: differentially Blank 4: methylated

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

Blank 1: nucleosomes Blank 2: loop Blank 3: lamina

If fully methylated DNA is introduced into a plant or animal cell, in subsequent generations the DNA will be . If the same sequence of nonmethylated DNA is introduced into a cell, it will be in daughter cells.

Methylated; nonmethylated

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

Posttranslational modifications of histones Binding of proteins to nucleosomes DNA methylation

Two genes that play a role in X-chromosome inactivation are ______.

Xist and Tsix

The function of TFIID is to ______.

bind to the TATA box and recruit RNA polymerase II to the core promoter

Consider a mouse that is homozygous for the loss-of-function mutation in the Agouti gene. What would be its fur color?

black

What effect can ATP-dependent chromatin remodeling have on transcription?

both activation and repression

Adult, wild-type mice with genotype AA for the Agouti gene will have coat hairs of which color?

brown with black tips

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

chromosomes

A protein that increases the rate of transcription but does not directly bind to the DNA is called a(n) .

coactivator

Activator proteins often increase transcription through an interaction with ______.

coactivators

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.

constitutive facultative

Which of these are molecular mechanisms that underlie epigenetic control of gene expression?

covalent histone modification chromatin remodeling DNA methylation localization of histone variants

The process that uses the energy of ATP hydrolysis to change the position or composition of nucleosomes is called ATP- remodeling .

dependent chromatin

In mice, the Agouti gene regulates the ______.

deposition of yellow pigment in hair

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

domains

The binding of a regulatory transcription factor to a(n) can stimulate transcription 10- to 1000-fold, which is called regulation.

enhancer up

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

DNA methylation, chromatin remodeling, covalent histone modification, and localization of histone variants are all molecular mechanisms that contribute to gene regulation.

epigenetics

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

facultative

True or false: Gene regulation may be related to epigenetic events such as the binding of transcription factors to certain genes, which induce permanent mutations in the DNA.

false

Higher-order heterochromatin structure is characterized by ______.

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

Gene regulation means that ______.

gene expression can be controlled so that genes can be expressed at high or low levels

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

higher order

Which type of enzyme can add acetyl groups onto the lysines of core histone proteins?

histone acetyltransferase

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

non coding

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

nuclear lamina

The core promoter of active genes is found in a(n) -free , which is a segment of DNA that is missing histones.

nucleosome region

A change in chromatin confirmation from closed to open often involves the movement of ______.

nucleosomes

Whether a gene is active or inactive often depends on the placement of at or near its promoter region.

nucleosomes

A protein that influences the ability of RNA polymerase to transcribe DNA into RNA is called a(n) .

transcription factor

In animals, the major protein that carries iron in the bloodstream is ______.

transferrin

True or false: The function of regulatory transcription factors is modulated in order to control the timing of gene expression.

true

True or false: The methylation state of DNA is inherited during cell division.

true

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

viral proliferation transposable element movement transcription

Female honeybee larvae fed with royal jelly during early development and nectar or pollen later in development will become ______ bees.

worker