Chapter 5 DNA and Chromosomes
Several experiments were required to demonstrate how traits are inherited. Which scientist or team of scientists first demonstrated that cells contain some component that can be transferred to a new population of cells and permanently cause changes in the new cells? (a) Griffith (b) Watson and Crick (c) Avery, MacLeod and McCarty (d) Hershey and Chase
A
Specific regions of eukaryotic chromosomes contain sequence elements that are absolutely required for the proper transmission of genetic information from a mother cell to each daughter cell. which of the following is not known to be one of these required elements in eukaryotes? (a) terminators of replication (b) origins of replication (c) telomeres (d) centromeres
A
The DNA from two different species can often be distinguished by a difference in the (a) ratio of A+T to G+C (b) ratio of A+G to C+T (c) ratio of sugar to phosphate (d) presence of bases other than A,G,C,T
A
The chromosomes we typically see in images are isolated from mitotic cells. These mitotic chromosomes are in the most highly condensed form. Interphase cells contain chromosomes that are less densely packed and __________________________. (a) occupy discrete territories in the nucleus. (b) share the same nuclear territory as their homolog. (c) are restricted to the nucleolus. (d) are completely tangled with other chromosomes.
A
The classic "beads-on-a-string" structure is the most decondensed chromatin structure possible and is produced experimentally. Which chromatin components are not retained when this structure is generated? (a) linker histones (b) linker DNA (c) nucleosome core particles (d) core histones
A
Which of the following best describes the mechanism by which chromatin-remodeling complexes "loosen" the DNA wrapped around the core histones? (a) They use energy derived from ATP hydrolysis to change the relative position of the DNA and the core histone octamer. (b) They chemically modify the DNA, changing the affinity between the histone octamer and the DNA. (c) They remove histone H1 from the linker DNA adjacent to the core histone octamer. (d) They chemically modify core histones to alter the affinity between the histone octamer and the DNA
A
Figure Q5-45 clearly depicts the nucleolus, a nuclear structure that looks like a large, dark region when stained. The other dark, speckled regions in this image are the locations of particularly compact chromosomal segments called ____________. (a) euchromatin. (b) heterochromatin. (c) nuclear pores. (d) nucleosomes.
B
Gene sequences correspond exactly to the respective protein sequences produced from them. This statement is false for two reasons. First, genes often contain intron sequences. Second, genes always contain nucleotides flanking the protein-coding sequences that are required for the regulation of transcription and translation.
False.
Hydrogen bonds between each nucleotide hold individual DNA strands together. Nucleotides are linked covalently through phosphodiester bonds. Hydrogen-bonding between nucleotides from opposite strands holds the DNA molecule together.
False.
There are five different nucleotides that become incorporated into a DNA strand. There are four different nucleotides that are used to make a DNA polymer: adenine, thymine, guanine, and cytosine. A fifth nucleotide, uracil, is found exclusively in RNA molecules, replacing thymine nucleotides in the DNA sequence.
False.
A nucleosome contains two molecules each of histones [H1 and H2A/ H2A and H2B] as well as of histones H3 and H4
H2A and H2B
Chromosomes exist at different levels of condensation, depending on the stage of the cell cycle.
True
Each strand of DNA contains all information needed to create a new double-stranded DNA molecule with the same sequence information
True
Eukaryotic chromosomes contain many different sites where DNA replication can be initiated
True
Linker histones help compact genomic DNA by influencing the path of the DNA after it has wrapped about the nucleosome core.
True
The polarity of a DNA strand results from the polarity of the nucleotide subunits.
True
Nucleosomes are present in [prokaryotic/eukaryotic] chromosomes, but not in [prokaryotic/eukaryotic] chromosomes
eukaryotic, prokaryotic
Nucleosome formation compacts the DNA into approximately [one-third/one-hundredth/one-thousandth] of its original length.
one-third
DNA molecules, like proteins, consist of a single, long polymeric chain that is assembled from small monomeric subunits. DNA is double-stranded. It is actually made of two polymers that are complementary in sequence.
False
Histone proteins have a lower than average number of lysines and arginines in their polypeptide chains
False
Interphase chromosomes represent a physical state of the chromatin with the highest order of packaging
False
The histone proteins that constitute the core nucleosome include tetramers of histones H2A, H2B, H3, H4
False
For a better understanding of DNA structure, it helps to be able to compare a physical characteristics evident from a side view of double-stranded DNA with those of individual base pairs (a) Use brackets to designate the major and minor grooves on Figure Q5-17A and shade in the surface that will be exposed in the major groove in Figure Q5-17B (b) if the base pairs were aligned and stacked directly on top of each other, the major and minor grooves would be linear depressions all along the DNA.
A
Many of the breakthroughs in modern biology came after Watson and Crick published their model of DNA in 1953. However, chromosomes were identified earlier. In what decade did scientists first identify chromosomes? (a) 1880s (b) 1920s (c) 1940s (d) 1780s
A
Methylation and acetylation are common changes made to histone H3, and the specific combination of these changes is sometimes referred to as the "histone code." Which of the following patterns will probably lead to gene silencing? (a) lysine 9 methylation (b) lysine 4 methylation and lysine 9 acetylation (c) lysine 14 acetylation (d) lysine 9 acetylation and lysine 14 acetylation
A
Mitotic chromosomes are ____ times more compact than a DNA molecule in its extended form. (a) 10,000 (b) 100,000 (c) 1000 (d) 100
A
Fred Griffith studied two strains of Streptococcus pneumonia, one that causes a lethal infection when injected into mice, and a second that is harmless. He observed that pathogenic bacteria that have been killed by heating can no longer cause an infection. But when these heat-killed bacteria are mixed with live, harmless bacteria, this mixture is capable of infecting and killing a mouse. What did Griffith conclude from this experiment? (a) The infectious strain cannot kill by heating (b) The heat- killed pathogenic "transformed" the harmless strain into a lethal one (c) the harmless strain somehow revived the heat killed pathogenic bacteria. (d) the mice had lost their immunity to infection with S. pneumoniae
B
Interphase chromosomes are about _____ times less compact than mitotic chromosomes, but still are about ______ times more compact than a DNA molecule in its extended form (a) 10, 1000 (b) 20, 500 (c) 5, 2000 (d) 50, 200
B
Mitotic chromosomes were first visualized with the use of very simple tools: a basic light microscope and some dyes. Which of the following characteristics of mitotic chromosomes reflects how they were named? (a) motion (b) color (c) shape (d) location
B
Most eukaryotic cells only express 20-30% of the genes they possess. The formation of heterochromatin maintains the other genes in a transcriptionally silent (unexpressed) state. Which histone modification directs the formation of the most common type of heterochromatin? (a) H3 lysine 4 methylation (b) H3 lysine 9 methylation (c) H3 lysine 14 methylation (d) H3 lysine 27 methylation
B
Stepwise condensation of linear DNA happens in five different packing processes. Which of the following four processes has a direct requirement for histone H1? (a) formation of "beads on a string" (b) formation of the 30-nm fiber (c) looping of the 30-nm fiber (d) packing of loops to form interphase chromosomes
B
The N-terminal tail of histone H3 can be extensively modified, and depending on the number, location, and combination of these modifications, these changes may promote the formation of heterochromatin. What is the result of heterochromatin formation? (a) increase in gene expression (b) gene silencing (c) recruitment of remodeling complexes (d) displacement of histone H1
B
The human genome is a diploid genome. However, when germ-line cells produce gametes, these specialized cells are haploid. What is the total number of chromosomes found in each of the gametes (egg or sperm) in your body? (a) 22 (b) 23 (c) 44 (d) 46
B
The information stored in the DNA sequences is used directly as a template to make (a) lipids (b) RNA (c) polypeptides (d)carbohydrates
B
The manner in which a gene sequence is related to its respective protein sequence is referred to as the _________ code. (a) protein (b) genetic (c) translational (d) expression
B
Which of the following is not a chemical modification commonly found on core histone N-terminal tails? (a) methylation (b) hydroxylation (c) phosphorylation (d) acetylation
B
Nucleosomes are aided in their formation by high proportion of [acidic/basic/polar] amino acids in histone proteins
Basic
How do changes in histone modifications lead to changes in chromatin structure? (a) They directly lead to changes in the positions of the core histones. (b) They change the affinity between the histone octamer and the DNA. (c) They help recruit other proteins to the chromatin. (d) They cause the histone N-terminal tails to become hyperextended.
C
Nucleosomes are formed when DNA wraps ______ times around the histone octamer in a _____ coil (a) 2.0, right-handed (b) 2.5, left-handed (c) 1.7, left-handed (d) 1.3, right- handed
C
The core histones are small, basic proteins that have a globular domain at the C-terminus and a long, extended conformation at the N-Terminus. Which of the following is not true of the N-terminal "tail" of these histones? (a) It is a subject to covalent modifications (b) it extends out of the nucleosome core (c) it bind s to DNA in a sequence- specific manner (d) it helps DNA packed tightly
C
The process of sorting human chromosomes pairs by size and morphology is called karyotyping. A modern method employed for karyotyping is called chromosome painting. How are individual chromosomes "painted"? (a) with a laser (b) using fluorescent antibodies (c) using fluorescent DNA molecules (d) using green fluorescent protein
C
What type of macromolecule helps package DNA in eukaryotic chromosomes? (a) lipids (b) carbohydrates (c) proteins (d) RNA
C
The telomere is a specialized DNA sequence where microtubules from the mitotic spindle attach to the chromosome so that duplicate copies move to opposite ends of the dividing cell. The telomere is a specialized DNA sequence, but not for the attachment of spindle microtubules. Telomeres form special caps that stabilize the ends of linear chromosomes.
False
When there is a well-established segment of heterochromatin on an interphase chromosome, there is usually a special barrier sequence that prevents the heterochromatin from expanding along the entire chromosome. Gene A, which is normally expressed, has been moved by DNA recombination near an area of heterochromatin. None of the daughter cells produced after this recombination event express gene A, even though its DNA sequence is unchanged. What is the best way to describe what has happened to the function of gene A in these cells? (a) barrier destruction (b) heterochromatization (c) epigenetic inheritance (d) euchromatin depletion
C
Which DNA base pair is represented in Figure Q5-18? (a) A-T (b) T-A (c) G-C (d) C-G
C
Which of the following structural characteristics is NOT normally observed in a DNA duplex? (a) purine-pyramidine pairs (b) external sugar-phosphate backbone (c) uniform left- handed twist (d) antiparallel strands
C
You are a virologist interested in studying the evolution of viral genomes. You are studying two newly isolated viral strains and have sequenced their genomes. You find that the genome of strain 1 contains 25% A, 55% G, 20% C, and 10% T. You report that you have isolated a virus with a single-stranded DNA genome. Based on what evidence can you make this conclusion? (a) single-stranded genomes always have a large percentage of purines (b) using the formula: G-A = C+T (c) Double-stranded genomes have equal amounts of A and T (d) single-stranded genomes have a higher rate of mutation
C
The structures of the four bases in DNA are given in Figure Q5-20? Which are purines and which are pyramadines? Which bases pair each other in double- stranded DNA?
C-T are pyramidines and A-G are purines; C pairs with G and A pairs with T
Hershey and Chase used radio labeled macromolecules to identify the material that contains heritable information. What radioactive material was used to track DNA during this experiment? (a) 3H (b) 14C (c) 35S (d) 32P
D
In a DNA double helix, (a) the two DNA strands are identical (b) purines pair with purines (c) thyamine pairs with cytosine (d) the two DNA strands run antiparallel
D
In the 1940s, proteins were thought to be more likely molecules to house genetic information. What was the primary reason that DNA was originally believed to be genetic material? (a) DNA has a high density of negative charges (b) Nucleotides were known to be a source of chemical energy of the cell (c) Both protein and nucleic acids were found to be components of chromosomes (d) DNA was found to contain only four different chemical building blocks.
D
The complete set of information found in a given organism's DNA is called its ____________ (a) genetic code (b) coding sequence (c) gene (d) genome
D
The human genome is divided into linear segments and packaged into structures called chromosomes. What is the total number of chromosomes food in each of the somatic cells in your body? (a) 22 (b) 23 (c) 44 (d) 46
D
The inactivation of one X chromosome is established by the directed spreading of heterochromatin. The silent state of this chromosome is _______________ in the subsequent cell divisions. (a) completed (b) switched (c) erased (d) maintained
D
The octameric histone core is composed of four different histone proteins, assembled in a stepwise manner. Once the core octamer has been formed. DNA wraps around it to form a nucleosome core particle. Which of the following histone proteins does not form part of the octameric core? (a) H4 (b) H2A (c) H3 (d) H1
D
Which of the following DNA strands can form a DNA duplex by pairing with itself at each position? (a) 5'- AAGCCGAA-3' (b) 5'- AAGCCGTT-3' (c) 5'- AAGCGCAA-3' (d) 5'- AAGCGCTT-3'
D
Which of the following chemical groups is NOT used to construct a DNA molecule? (a) five-carbon sugar (b) phosphate (c) nitrogen-containing base (d) six- carbon sugar
D
Which of the following questions would not be answered by using karyotyping? (a) is the individual genetically female or male? (b) Do any of the chromosomes contain pieces that belong to other chromosomes? (c) Does the individual have an extra chromosome? (d) Do any chromosomes contain point mutations?
D
All functional DNA sequences inside a cell code for protein products Some sequences encode only RNA molecules, some bind to specific regulatory proteins, and others are sites where specific chromosomal protein structures are built (for example, centromeric and telomeric DNA).
False.
Comparing the relative number of chromosome pairs is a good way to determine whether two species are closely related. There are several examples of closely related species that have a drastically different number of chromosome pairs. Two related species of deer—Chinese and Indian muntjac—have 23 and 3, respectively
False.
Gene expression is the process of duplicating genes during DNA replication. Gene expression is the process of going from gene sequence to RNA sequence, to protein sequence.
False.
