Bio 305- Chapter 12

Ways that nucleosomes can change

-Change in location -Covalent modifications to the amino-terminal tails of histones

Which roles does the noncoding Xist RNA play in X-chromosome inactivation?

-Coats the X chromosome that will be inactivated -Recruits histone modifying enzymes to the X chromosome that will be inactivated

Chromatin is a complex of _____ and _____ found within eukaryotic chromosomes

-DNA -Protein

Events of nucleosome assembly in order from earliest to latest

1) Newly sythesized DNA is formed 2) An H3-H4 teramer binds 3) Two H2A-H2B dimers bind

Steps involved in fluorescence in situ hybridization (FISH) in correct order

1) Obtain cells in the metaphase stage of mitosis 2) Drop cells on a slide and treat them wiht agents that cause them to burst 3) Denature chromosomal DNA 4) Hybridize chromosomal DNA to a single-stranded DNA probes that are tagged with a fluorescence lable 5) View with a fluorescence microscope

What is an artificial chromosome?

A cloning vector that can accept large DNA inserts and be passed on like a chromosome in a living cell

Which of the following describes the nucleic acid molecule(s) found in a single eukaryotic chromosome (or a chromatid if the chromosome has been replicated)?

A single, long, linear molecule of double-stranded DNA

Chromatin that can interconvert between heterochromatin and euchromatin is called ____ heterochromatin

Facultative

Which is the best description of an inactivated X chromosome in a somatic cell of a human female?

Facultative heterochromatin

T or F: Heterochromatin is transcriptionally active

False

In Drosophila, a protein that binds to methylated histone H3 tails and promotes the formation of heterochromatin is

HP1

Which one represents the highest level of chromosome compaction that has been observed or hypothesized?

Radial loop-scaffold

If a segment of chromatin is subjected to histone deacetylation, it will likely

become more condensed, which will repress gene expression

An enzyme that removes acetyl groups from histone proteins is called histone

deacetylase

Which of the following causes of genetic disorders can be detected with FISH analysis?

deletions, duplications, translocations

The initiation of X-chromosome inactivation occurs in the human

embryo, about two weeks after fertilization

Regions of chromosomes that have less condensed chromatin are called

euchromatin

A region of a chromosome with highly compacted chromatin is called

heterochromatin

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

Histone acetylation

prevents close packing of nucleosomes and therefore favors gene expression

Electron microscope studies of chromatin have detected a 300 Angstrom fiber that is formed by

supercoiling of nucleosomes

Telomere sequences

-Do not encode proteins -Consist of short repeated sequences

The nucleosome core includes two each of four histones named _____, _____, ______, and ______.

-H2A -H2B -H3 -H4

What are the core histones of the nucleosome?

-H2A -H2B -H3 -H4

In a nucleosome, the DNA can associate with the histone proteins because the DNA has a _____ charge and the histone proteins have a _____ charge

-Negative -Positive

Nonhistone proteins are responsible for

-Regulating transcription and RNA processing - enzymatic activity in DNA replication - assisting with chromosome segregation -Forming the structural backbone if the chromosome

N-terminal tails of histones can be chemically modified by the addition of _____ and/or _______ groups.

-acetyl -methyl

Which features distinguish the centromeres of higher eukaryotes from yeast centromere sequences?

-bind to many microtubules -larger -contain many more repeating units

The RNA component of the telomerase enzyme is

-complementary to the repeated sequences in telomeres - used as a template to add new repeats to the ends of telomeres

For histone methylation, histone _____ add methyl groups and histone _____ remove methyl groups.

-methyltransferases -demethylases

The noncoding RNA molecule called Xist

-never leaves the nucleus -is never translated into a protein

To distinguish between the portions of the chromosome on either side of the centromere, geneticists use the letter ______ to denote the shorter arm and the letter ______ to indicate the longer arm

-p -q

The inactivated X chromosome is somatic cells or mammals, like the red-staining structure labeled Xi in the image, is called ______ ______.

Barr body

DNA elements that prevent the spread of heterochromatin into regions of euchromatin are called

Barrier elements

Protein complexes that help in the compaction of interphase chromosomes into metaphase chromosomes are called

Condensins

Cohesin is a protein complex that

Holds sister chromatids together

As a general rule, the less frequently a DNA segment is transcribed, the _______ it is compacted

More

Which molecule found within eukaryotic chromosomes is responsible for the compaction of chromosomes?

Protein

DNA extending from one origin of replication to the endpoints where it merges the DNA from adjoining replication forks is called a

Replicon

A short DNA sequence of 5-300 base pairs that is repeated from thousands to millions of times in tandem is called ___ DNA

Satellite

Form the octamer of core histone proteins in a nucleosome

Two of each -H2A -H2B -H3 -H4

In somatic cells of human females one of the two X chromosomes is randomly turned off. What is this mechanism called?

X-chromosome inactivation

The 450 kb region on the X chromosome that plays an important role in X chromosome inactivation is the _______

XIC

The gene that produces a noncoding RNA that is essential for X-chromosome inactivation is called

Xist

DNA sequences found within constitutive heterochromatin include _____ elements and long stretches of simple _____ sequences

_transposable -repetitive

The Xist gene produces _______, leading to inactivation

a noncoding RNA that coats the X chromosome

In chromatin, it is possible to detect when a gene is activated because its promoter region becomes DNase

hypersensitive

Diagrams of the chromosomal banding patterns produced by G-banding are called

idiograms

During in situ hybridization, a DNa probe made from a cloned gene binds to ______.

its complementary sequence on a particular chromosome

Chromosomal division in eukaryotes, spindle fibers attach to

kinetochores

Fluorescent in situ hybridization (FISH) is a method used to

locate specific DNA sequences on chromosomes displayed in a karyotype

A situation where heterochromatin can prevent the expression of a nearby gene in some cells but not others is called ______ -_______ variegation

position-effect

Nonhistone proteins assist with a number of processes such as DNA replication and chromosome segregation, but the majority of nonhistone proteins serve to

regulate transcription and RNA processing during gene expression

Histone deacetylase is an enzyme that _______ acetyl groups from/on histone N-terminal tails

removes

An enzyme that restores sequences to extend the ends of chromosomes is called

telomerase

Each end of a eukaryotic chromosome has a protective structure called a(n)

telomere