Chapter 15 BIO 210 Genetics

DNA methyltransferase is an enzyme that attaches a methyl group to the position ______ of the _______ base.

5 (5'); cytosine

What DNA sequence is methylated?

5'-CG-3'

What are examples of epigenetics?

Covalent histone modification Localization of histone variants Chromatin remodeling DNA methylation

When iron levels are abundant in the cytosol, iron binds to the ____, enabling the translation of ______ mRNA.

IRP; ferritin

What are ways that heterochromatin can inhibit transcription?

Inhibiting the recruitment of general transcription factors or coactivators Preventing activators from binding to enhancer sequences

How does iron regulatory protein exert its effect on ferritin mRNA?

Iron regulatory protein (IRP) binds to the iron response element (IRE) in the 5' UTR, and thus inhibits ferritin translation.

What examples of how gene regulation benefits eukaryotic organisms?

The ability to respond to environmental stresses The ability to respond to changes in nutrient availability

A regulatory transcription factor that enhances the rate of transcription is called a(n) ______

activator

The CREB protein is a regulatory transcription factor that is activated following an increase in ______

cAMP

Gene regulation means that ______.

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

Human nerve cells and muscle cells look quite different from each other due to differences in ______.

gene regulation

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

heterochromatin protein 1 (HP1)

Core ____ proteins contain a globular domain and a flexible amino-terminal tail. DNA wraps around the globular domains, and the amino-terminal tails protrude from the chromatin.

histone

Positively charged _____ within core histone proteins can be acetylated by histone ______

lysines; acetyltransferases

If chromatin is in a closed conformation, nucleosome position and histone composition ______.

make it difficult for transcription factors to gain access to and bind their target sequences in the promoter DNA

CpG islands near the promoters of tissue-specific genes are often ____

methylated

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

non-coding

DNA sequences that are analogous to the operator sites found near bacterial promoters are called ____ elements or ______ sequences

regulatory; regulatory

Regulatory transcription factors that prevent transcription from occurring are called _____

repressors

The cAMP regulatory ____ element-binding protein (_____ protein_ is a regulatory transcription factor that is activated in response to signaling molecules that increase cytoplasmic cAMP.

response; CREB

Repressors bind to ______.

silencers

What is the organism with the highest amount of DNA methylation?

vertebrates

What affect does acetylation have on lysines in core histone protein tails?

Eliminates the positive charge on lysine, disrupting the electrostatic attraction between the histone and the negatively charged DNA backbone

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

False

What are the histones for which variants have been identified?

H2A H2B H3 H1

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

chromatin structure with the stage of the cell cycle

Interphase matches Choice, Most chromosomal regions are composed of euchromatin. Most chromosomal regions are composed of euchromatin. M phase matches Choice, Euchromatic regions condense into constitutive and facultative heterochromatin. Euchromatic regions condense into constitutive and facultative heterochromatin. M phase through interphase in two daughter cells matches Choice, Constitutive and facultative heterochromatin regions retain the same pattern observed in mother cell. Constitutive and facultative heterochromatin regions retain the same pattern observed in mother cell.

What are some of the common types of covalent modifications made to the amino-terminal tails of histones?

Methylation Acetylation Phosphorylation

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

Preventing viral proliferation Silencing genes Preventing movement of transposable elements

If gene regulation acts to prevent translation, what molecule will not be produced?

Protein

What regulates iron assimilation in mammalian cells?

RNA binding proteins

How does heterochromatin prevent the movement of transposable elements (TEs)?

Silencing genes needed for transposition

Select the steps at which gene regulation can occur.

Transcription Translation Posttranslational modification RNA processing

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

Transcription Viral proliferation Transposable element movement

The role of heterochromatin in repressing transcription may be due to interference with which of the following factors?

Transcriptional activators Coactivators General transcription factors

What 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 of the following are true regarding epigenetics?

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

What is true regarding epigenetics?

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

If chromatin is in a ____ conformation, transcription may be difficult or impossible.

closed

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

constituative

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

DNA sequences in eukaryotes that can be bound by regulatory transcription factors, which then affect the ability of RNA polymerase to transcribe a particular gene are called ______.

control elements regulatory sequences regulatory elements

DNA methylation is the ____ attachment of methyl groups to DNA.

covalent

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

Plants and animals require a greater level of gene regulation than single-celled eukaryotes because of ______.

different tissue types different developmental stages multicellularity more complex cell structure

Regulatory elements that inhibit transcription are called silencers and their effect on transcription is called ______ regulation.

down

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

enhancer; up

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 ____

epigenetics

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

epigenetics

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

facultative

Methylation of the cytosine in both strands is called _____ methylation, and methylation of only one strand is called ____

full ;hemimethylation

Genes that code for proteins that are required in most cells of a multicellular organism are called ______.

housekeeping genes

A sequence found in both ferritin and transferrin receptor mRNAs that is recognized by an RNA-binding protein is called the ______.

iron response element

In order to regulate the translation of both ferritin and transferrin receptor mRNAs, the iron regulatory protein (IRP) binds to the _____ of the mRNAs. Multiple choice question.

iron response element

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; unmethylated

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

nucleosome; DNA; histone

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

nucleosomes

The placement of ____ at or near promoters often plays a key role in whether a gene is active or inactive.

nucleosomes

When chromatin is accessible to transcription factors and RNA polymerase, it is referred to as being in the ______ conformation.

open

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

'' The ability of humans to develop tans to protect their skin cells from UV rays by inducing genes that provide protection against UV radiation is an example of gene ___

regulation

The phenomenon where the level of gene expression is controlled so that genes can be expressed at high or low levels is called gene ___

regulation

When sites containing transposable elements (TEs) are converted to heterochromatin, the TEs are prevented from moving because the genes for transposition are ______.

silence

Binding of IRP to the iron response element (IRE) 3'-UTR ______

stabilizes the transferrin receptor mRNA

Genes that are highly regulated and may be expressed only in certain cell types are called _______ genes

tissue-specific

A ____ is a protein that influences the ability of RNA polymerase to transcribe a given gene.

transcription factor

The cytosines in CpG islands near housekeeping genes are ______

unmethylated

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 is an example of epigenetic inheritance?

Methylation of DNA that occurs in an oocyte

You are studying a transcription factor that binds to DNA near a gene of interest. You discover that once the transcription factor binds, transcription of your gene of interest becomes undetectable. This is an example of ______.

down regulation

Activators bind to ______.

enhancers

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

true