Chapter 12 Reading Quiz
So that the bacterial chromosome can fit within the cell it must be compacted about ___ fold
1000
So that the bacterial chromosome can fit within the cell, it must be compacted about ______ fold.
1000
What length of DNA is associated with a nucleosome?
146 to 147
How many chromosomes and sets of chromosomes are found in a normal human somatic cell?
2 sets of 23
In a normal human somatic cell there are two sets of chromosomes and each set contains _____ chromosomes
23
What is a chromosome territory?
A discrete region in the nucleus where a chromosome is located
If you knew that a chromosome had multiple origins of replication, what kind of cell would you predict it came from?
A eukaryotic cell
Approximately how many times do moderately repetitive sequences appear in a genome?
A few hundred to several thousand times
Generally, how large is a bacterial chromosome?
A few million base pairs
Generally, how large is a bacterial chromsome?
A few million base pairs
What are the features of a point centromere such as those found in certain yeast species?
Approximately 125 bp long Defined DNA sequence
What are the main characteristics of the nucleoid?
Bacteria may have more than one chromosome, each within its own nucleoid region. The nucleoid is in direct contact with the cytoplasm.
The sequence of DNA involved in the segregation of chromosomes, upon which the kinetochore assembles, is called the ______-
Centromere
What is the name of the complex of DNA and protein found within eukaryotic chromosomes?
Chromatin
The antibiotic ciprofloxacin is selectively toxic (kills bacteria but not eukaryotic cells). What is the mechanism of action of this selective toxicity?
Cipro blocks bacterial DNA gyrase but not eukaryotic topoisomerases.
Aside from a few exceptions, what is the general structure of bacterial chromosomes?
Circular
Chromatid is the complex of ___ and ___ found within eukaryotic chromsomes
DNA Protein
Order the levels of chromatin compaction from the least condensed at the top of the list to the most condensed at the bottom of the list.
DNA double helix wrapping DNA around histones formation of 30nm fiber formation of radial loops heterochromstin in mitotic chromsomes
The activities of which two enzymes 'compete' to govern the overall supercoiling of DNA?
DNA gyrase and topoisomerase I
What are topoisomers?
Different forms of DNA that differ only in the extent and nature of supercoiling
A chromosome that is linear, millions of base pairs long, has a centromere, two telomeres, and multiple origins of replication is from which type of cell?
Eukaryotic
What kind of cell would contain linear chromosomes found in sets and located in a nucleus?
Eukaryotic Cell
What are the defining features of eukaryotic chromosomes
Found in nucleus Linear Present in one or more sets
Which is an example of a moderately repetitive sequence?
Genes encoding ribosomal RNA (rRNA)
What is true of histone H1?
It binds between nucleosomes. It binds DNA. It is called the linker histone.
What are the characteristics of a regional centromere?
Larger than point centromeres Contain tandem arrays of repetitive DNA sequences Range in size from several thousand to over a million base pairs long Found in more complex eukaryotes
In terms of genome structure, what is a tandem array?
Many repeats of a short nucleotide sequence in a row
Which topoisomer of DNA is found in living bacterial cells?
Negatively supercoiled
Which structure(s) are NOT present in a typical bacterial cell?
Nucleus Telomeres
With respect to eukaryotic genomes what is sequence complexity
Number of times a particular sequence appears in the genome
Which type of centromere is characterized by a defined DNA sequence with a length of about 125 bp, and can be found in certain species of yeast?
Point centromere
What are the key features of eukaryotic chromosomes?
Possess centromeres Multiple origins of replication Linear Possess telomeres Tens of millions to hundreds of millions of base pairs long Occur in sets (e.g. diploid)
What are the functions of telomeres?
Prevention of chromosomal shortening Prevention of chromosomal rearrangements
What kind of sequence accounts for the majority of the DNA in a bacterial genome?
Protein-encoding genes
In bacterial genomes, what are the functions of repetitive sequences of DNA?
Recombination DNA folding Gene regulation
What is euchromatin
Regions of chromosomes that are less condensed
What is euchromatin?
Regions of chromosomes that are less condensed
What is the function of topoisomerase I?
Relax negative supercoils in DNA
Which kinds of DNA sequences are typically present in the genomes of bacteria?
Sequences regulating DNA folding Sequences regulating gene transcription Origin of replication Protein encoding regions Intergenic sequences
Approximately how large is a typical eukaryotic gene?
Several thousand to tens of thousands of base pairs
In the diagram of the nucleosome, to what do the arrows point?
Solid arrows: core histones; Dashed arrow: DNA
Which of the following are DNA sequences required for the replication and segregation of eukaryotic chromosomes?
Telomeres at ends of chromosomes Centromeres Origins of replication
What DNA sequences are required for the replication and segregation of eukaryotic chromosomes?
Telomeres, centromeres, and origins of replication
What are the key features of bacterial chromosome organization and structure?
The chromosome is generally circular. The chromosome is about a few million base pairs long. The chromosome has a single origin of replication. The chromosome generally has thousands of different genes.
What is the name of the structure that assembles on the centromere and connects the centromere to the mitotic spindle to ensure the proper segregation of chromosomes?
The kinetochore
In a nucleosome, what is the nature of the chemical attraction between the histone proteins and the DNA?
The positively charged histone proteins are attracted to the phosphate groups along the DNA backbone.
What is heterochromatin?
The tightly compacted regions of chromosomes
Which enzyme can relax the negative supercoils found in DNA?
Topoisomerase I
Which enzyme introduces negative supercoils into DNA?
Topoisomerase II
What is the composition of the octamer of core histone proteins in a nucleosome?
Two H2A, two H2B, two H3, two H4
Which of these form the octamer of core histone proteins in a nucleosome?
Two H3 Two H4 Two H2B Two H2A
What is a transposable element?
What is a transposable element?
Where on a eukaryotic chromosome are telomeres located?
Where on a eukaryotic chromosome are telomeres located?
If you knew that a chromosome had a single origin of replication, from what kind of cell would you predict it came?
a bacterium
One of the highly repetive sequences in the human genome is the ___ sequence, which is about 300 bp long and found in about 1,000,000 copies in the genome
alu
If you were told that a chromosome was about a million base pairs long, had a single origin of replication, was circular, and contained about a thousand genes, then you would be confident that the chromosome was from a(n)_____
bacteria
If someone told you that an organism's genome had a single origin of replication that was a few hundred nucleotides in length, what kind of organism would you suspect that genome came from?
bacterial
With a few exceptions bacteria chromosomes are __- in shape
circular
The number of times a particulat base sequence appears in a genome is referred to as sequence____
complexity
Highly repetitive sequences can be described as ______.
elements found in tens of thousands or millions of copies per genome often transposable elements, such as the Alu sequence
Telomeres are located on both ___ of the eukaryotic chromosome
ends
True or false: Heterochromatin is transcriptionally active.
false
True or false: There is a close relationship between the complexity of a eukaryotic organism and genome size.
false
The antibiotic ciprofloxacin is able to kill bacteria but not eukaryotic cells because it is able to inactivate bacterial DNA _______ but not eukaryotic topoisomerases.
gyrase
Since chromosomes are highly compacted during M phase, they ______.
have little transcriptional activity
Regions of chromosomes with highly compacted chromatin are called ______.
heterochromatin
What is the transcriptional activity of heterochromatin?
inactive
The group of proteins that assembles on the centromere to attach the chromosome to the spindle apparatus is called the_____
kinetichore
When comparing bacterial and eukaryotic genomes, the bacterial genome is generally smaller and, therefore, contains ______ DNA and fewer ______.
less, genes
The E. coli chromosome is organized into ______ that are about 800 to 1000 kilo base pairs (kbp) in length.
macrodomains
In E. Coli the chromosome has 400-500 loops called ___ with about 10000 bp of DNA in each loop
microdomains
In E. Coli the chromosome has 400-500 loops called ______ with about 10000 bp of DNA in each loop
microdomains
Generally speaking a bacterial chromosome is usually a few
million
Sequences appearing a few hundred to several thousand times in a genome are called ____ repetitve sequences
moderately
sequences appearing a few hundred to several thousand times in a genome are called ____ repetitive sequences
moderately
If we compared the amount of DNA in the genome of a eukaryote to the amount of DNA in a bacterium would generally find that there is ______ DNA in the genome of a eukaryote than in the genome of a bacterium. This means there is likely a greater number of genes in the genome of the eukaryote.
more
In a nucleosome, the DNA can associate with the histone proteins because the DNA has a(n) ---- charge and the histone proteins have a ____ charge
negative positive
Which feature of bacterial chromosomes facilitates both replication and transcription?
negative supercoiling
The chromosomal DNA in living bacteria is -_______ supercoiled
negatively
The chromosomal DNA in living bacteria is _____ supercoiled
negatively
The region of the bacterial cell where the chromosome(s) is/are located, and where the chromosomes are in direct contact with the cytoplasm is called the ______
nucleoid
The region of the bacterial cell where the chromosomes is/are located and where the chromosomes are in direct contact with the cytoplasm is called the _____
nucleoid
The DNA in a _____ wraps around the core octamer of histone proteins and it takes 146 or 147 base pairs of DNA to form this structure
nucleosome
In eukaryotic cells, chromosomes reside within the bounded compartment known as the
nucleus
In eukaryotic cells, chromosomes reside within the bounded compartment known as the_____-
nucleus
In bacteria, negative supercoiling of the chromosome benefits the cell by ______.
promoting strand separation for replication compacting the DNA promoting strand separation for transcription
Which molecule found within eukaryotic chromosomes is responsible for the compaction of chromosomes?
protein
Of the two main types of molecule found within eukaryotic chromosomes, ___ are laegely responsible for chromosome compaction
proteins
In some cases, moderately repetitive sequences are multiple copies of the same gene; for example, the genes which encode the _____ required for ribosome function are moderately repetitive sequences.
rRNA
Centromeres found in higher eukaryotes that range in size from several thousands to over a million base pairs in length and that have tandem arrays of repetitive sequences are called _______ Centromeres
regional
Gene regulation, DNA folding, and genetic recombination are all regulated by intergenic sequences of DNA in multiple copies called ___ sequences
repetitive
The centromere plays a role in
segregation of eukaryotic chromosomes
The centromere plays a role in the ______.
segregation of eukaryotic chromosomes
In many cases, variations in the ____ of eukaryotic genomes are not related to the complexity of the species.
size
Due to the fact that the two strands of DNA in a double helix are wound around one another twisting forces applied to the DNA double helix result in the introdiction of additional coils a process known as
supercoiling
The competing activities of DNA gyrase and topoisomerase I govern the overall level of in ______DNA.
supercoiling
What would you call the additional coils that form when a double helix of DNA is subject to twisting forces?
supercoils
A group of very short sequences of nucleotides that are repeated over and over is called a(n)_______
tandem array
The chromosomal structures that prevent both chromosomal shortening and chromosomal rearrangements are called______-
telomeres
Highly repetitive sequences are found in ______ of copies throughout a genome.
tens of thousands or millions
A discrete region of the nucleus where a chromosome is located is known as a chromosome_____-
territory
A discrete region of the nucleus where a chromosome is located is known as a chromosome______
territory
How much of the sequence information in a bacterial genome is dedicated to encoding proteins?
the majority
To fit into a bacterial cell, the bacterial chromosomes must be compacted approxiamtely one-___fold
thousand
'' A typical eukaryotic gene ranges in size from several thousand to tens of _______ , Incorrect Unavailable of base pairs.
thousands
A typical eukaryotic gene ranges in size from several thousand to tens of ___ of base pairs.
thousands
In the human genome sequence, about how many copies of the Alu sequence would you expect to find on each chromosome?
thousands or more
Following DNA replication, the two new molecules of DNA can sometimes be intertwined. The enzyme responsible for untangling the two molecules is called _____ ______
topoisomerase II
DNA molecules that differ in the extent and nature of their supercoiling are referred to as______
topoisomers
a segment of DNA with the ability to move within a genome is called a(n) ________ element
transposable
True or false: Histone H1 binds to the DNA between nucleosomes.
true
True or false: Transcriptional activity essentially ceases during mitosis because of chromosome compaction.
true
