SB Ch 13 Eukaryotic Chromosome
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 is a complex of
DNA and protein
Which is the best description of an inactivated X chromosome in a somatic cell of a human female?
Facultative heterochromatin
Which enzymes accomplish the addition of acetyl groups to lysine residues in histone tails?
Histone acetyltransferases
As double-stranded daughter DNA strands form at the replication fork, they are immediately organized in the form of nucleosomes, which are composed of
a random mixture of recycled and newly formed histones
A kinetochore is a chromosomal structure where
a spindle fiber will attach during chromosomal division
A synthetic yeast chromosome
entirely human-made in a DNA synthesizer machine
Chromosome centromeres are
essential for precise distribution of chromosomes during cell division the sites where sister chromatids are most tightly bound together the sites where kinetochores form, to allow spindle fiber attachment
Regions of chromosomes that are heterochromatic in some cells and euchromatic in other cells of the same organism are called ____ heterochromatin.
facultative
Scientists have generated a yeast with a single giant chromosome. To do that, they
fused all normal yeast chromosomes and removed all but one centromere and two telomeres
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
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
Modification of histone N-terminal tails occurs by the addition of __ groups to specific lysines and arginines and/or __ groups to specific lysines.
methyl; acetyl
As a general rule, the less frequently a DNA segment is transcribed, the __ it is compacted.
more
Before DNA replication, all eukaryotic chromosomes contain
one linear, double-stranded DNA molecule
What is facultative heterochromatin?
regions that become heterochromatic depending on cell types.
DNA extending from one origin of replication to the endpoints where it merges with the DNA from adjoining replication forks is called a
replicon
Telomerase is an enzyme that
restores sequences at the ends of chromosomes
A short DNA sequence of 5-300 base pairs that is repeated from thousands to millions of times in tandem is called
satellite
What is a Barr body?
An inactivated X chromosome in mammalian somatic cells
Enzymes called histone acetyltransferases
add acetyl groups to specific lysine residues in a histone
Replication of the ends of a linear DNA molecule is problematic because
DNA polymerase can only add nucleotides at the 3' end of a growing DNA strand
Scientists have been able to assemble metaphase chromatids in vitro using protein extracts from African frog eggs. Which of the following lists the minimum complement of proteins required for this process?
Histones, histone chaperones, condensins, and topoisomerase II
Working with protein extracts from African frog eggs, scientists have been able to disassemble and reassemble metaphase chromosome. Which of the following proteins were sufficient (when used together) for chromosome assembly in vitro?
Histones, histone chaperones, condensins, and topoisomerase II
Which features distinguish eukaryotic chromosomes from bacterial chromosomes?
In eukaryotic chromosomes, DNA is wound into nucleosomes. Eukaryotic chromosomes are linear. Eukaryotic chromosomes contain more DNA.
Are DNA compaction and gene expression related and if so, how?
In general, the more a segment of DNA is transcribed, the less it is compacted
What is the histone composition of a nucleosome that has just been assembled on a newly replicated DNA molecule?
It contains a random mixture of newly formed and recycled histones
What size DNA fragments are usually cloned using yeast artificial chromosomes?
Larger than 100 kb
The basic unit of chromatin is the nucleosome. At the next level of compaction, the DNA of chromosomes is organized in the form of ____ with the help of protein complexes called ___
Loop, condensin
What are two common and well understood histone tail modifications?
Methylation Acetylation
A replicon includes DNA duplicated from __ origin of replication
One
Which of the following would be found in a Yeast Artificial Chromosome (YAC) that is used for molecular cloning?
Origin of replication Telomere Centromere Selectable marker Large fragment of foreign DNA
What is facultative heterochromatin?
Regions of chromosomes that heterochromatic in some cells and euchromatic in other cells
The types of modifications found on histone determine the packing of , as well as the ability of the tails to bind chromatin modifying proteins.
Tails, nucleosomes
The types of modifications found on histone — determine the packing of —- as well as the ability of the tails to bind chromatin modifying proteins.
Tails, nucleosomes
Each end of a eukaryotic chromosome has a protective structure called a(n)
Telomeres
Scientists have been able to generate a yeast strain that has a single giant chromosome. Choose all features of this cell.
The giant chromosome has a single centromere. The cell behaves like wild type but cannot produce viable spores when crossed with normal yeast. The giant chromosome has two telomeres.
What is heterochromatin?
The tightly compacted regions of chromosomes
What is the composition of the nucleosome core?
Two H2A, two H2B, two H3, two 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
What is the primary role of the 450 kb region of DNA in the human X chromosome known as the XIC?
X-chromosome inactivation
A cloning vector that can accommodate a large DNA insert and behave like a chromosome when it is inside a living cell is called an ____ chromosome
YAC
Immediately after it is synthesized, a synthetic yeast chromosome contains
all of the genes present on the corresponding yeast chromosome
The protein that forms a complex to hold sister chromatids together is called
cohesin
Protein, ring-shaped complexes that help form loops during the compaction of DNA in chromosomes, are called
condensins
In humans with a typical constitution of chromosomes, X-chromosome inactivation induces dosage compensation by randomly inactivating one of the X chromosomes in the somatic cells of
females
Cohesin is a protein complex that
holds sister chromatids together
During chromosomal division in eukaryotes, spindle fibers attach to
kinetochores
Unlike bacterial chromosomes, eukaryotic chromosomes are _blank_, have _blank_ DNA, and have the DNA organized into _blank_.
linear; more; nucleosomes
Fluorescence in situ hybridization (FISH) is a method used to
locate specific DNA sequences on chromosomes displayed in a karyotype
The noncoding RNA molecule called Xist
never leaves the nucleus and is never translated into a protein
The product of the Xist gene is a long RNA molecule that is never translated. Such RNA molecules are called long
noncoding
The basic unit of chromatin is the ____ which consists of DNA wound around a core of
nucleosome & histone
Histone proteins can be chemically modified by adding acetyl or methyl groups to __ which extend outward from the nucleosome.
their N-terminal tails
The predominant satellite found in human centromeres is called
α-satellite
