Genome sequencing and analysis projects have revealed that eukaryotic DNA consists of variable amounts of
A) adenine and thymine.
B) repetitive sequences.
D) cytosine and guanine.
A nucleoside consists of a
A) pentose sugar and a nitrogenous base.
B) phosphate group and a nitrogenous base.
C) pentose sugar and a phosphate group.
D) pentose sugar, a phosphate group, and a nitrogenous base.
Genes located in which region of a eukaryotic chromosome are most likely to be transcribed?
In all types of cells, there is (are) at least ___ type(s) of RNA molecules.
DNA strands are considered antiparallel because the strands are oriented in opposite directions. Each nucleotide strand has a 5'-3'' or 3'-5' directionality. What is the basis of this DNA polynucleotides directionality?
A) Five free carbons at one end of a polynucleotide chain, and three free carbons at the other end.
B) The phosphodiester linkage points of the nucleotides, linking the 5' carbon and 3' -OH group of each unit.
C) The designation is arbitrary, stemming from the experiments used to identify the structure.
D) The 5' end has five hydrogen bonds, and the 3' end has three.
In general, most bacterial cells contain ___ chromosome(s).
In his transformation experiments, Frederick Griffith observed that virulent strains of Streptococcus pneumoniae produced smooth, shiny colonies whereas avirulent strains produced rough colonies. Working from this observation, what important principle of molecular genetics did Griffith demonstrate in his experiments?
A) That smooth, shiny colonies result from a bacterial capsule created by the bacterium when it was grown on agar plates.
B) That a transforming principle (a substance) present in cells carries the information for the production of genetic traits carried by the organism.
C) That when cells are killed, they are no longer virulent.
D) That both virulence and smoothness could be conditioned by the same gene.
What was the major conclusion of the Hershey and Chase bacteriophage experiments?
A) single gene directs the synthesis of a single polypeptide.
B) DNA, but not protein, is the genetic material.
C) DNA is a double helix.
D) The genetic material is located in the nucleus of cells.
The plant pathogen Agrobacterium tumefaciens produces crown gall disease by transferring a piece of DNA from the bacterium into the nuclear genome of a plant cell. This DNA contains genes that are needed to produce the tumorous tissue grown called crown gall disease. Biotechnologists have learned that replacing the disease-causing DNA in the bacteria with DNA for genes of interest can genetically modify plants in useful ways. Which of the classical experiments of molecular genetics, done with prokaryotes, does this technology confirm in eukaryotes?
A) Griffith's transformation experiment
B) Avery's transformation experiment
C) Hershey and Chase's bacteriophage experiment
D) Both answer #2 and #3 are confirmed in eukaryotes by plant transformation technology.
Prokaryotic chromosomes consist of
A) unique-sequence DNA only.
B) repetitive-sequence DNA only.
C) either unique-sequence or repetitive-sequence DNA.
D) both uunique-sequence and repetitive-sequence DNA.
The DNA and histone proteins in a eukaryotic chromosome are compacted into structures called
The DNA molecules of the human genome are approximately
2 meters long, but they are able to execute all of their
functions-including replication, transcription, and
regulation-remaining inside a cell nucleus that is typically less
than 100 micrometers in diameter. In eukaryotes, DNA is organized at
a number of levels to keep these molecules from being hopelessly
tangled. The following is a list of organizational levels of
A. Visible chromosomes consisting of sister chromatids
B. Nucleosomes organized to form 30-nanometer chromatin threads
C. Looped 30-nanometer chromatin threads attached to the chromosome scaffold proteins
D. DNA molecules wrapping around histone proteins to make nucleosomes
E. DNA molecule containing the genetic code
The proper order of organization from most highly organized to least organized is
A) A > B > C > D > E.
B) E > D > C > B > A.
C) A > C > B > D > E.
D) E > C > B > D > A.
The DNA that makes up bacterial chromosomes is typically
B) circular and supercoiled.
C) complexed with histones.
D) all of the above
The human genome contains approximately ___ times more DNA than the genome of the bacterium Escherichia coli .
DNA denatures (is structurally disrupted) at a higher temperature than does most proteins, yet DNA structure depends on relatively weak hydrogen bonds. Why is DNA so stable to denaturation by high temperature?
A) Proteins are denatured by breaking covalent bonds.
B) Linear molecules like DNA are inherently stable.
C) Individual hydrogen bonds may be weak, but DNA structure is stabilized by many thousands or millions of these bonds-far more than are found in proteins.
D) The statement is incorrect; it actually takes far more energy to denature proteins than it does to denature DNA.
The type of DNA found most commonly in living cells is the ___ form.
Down syndrome is a genetic disorder that occurs when individuals have an extra copy of chromosome 21. How might you confirm this condition in a newborn?
A) Determine the DNA content of a cell (C-value).
B) Examine the chromosome structure of the newborn.
C) Determine the karyotype of cells in metaphase from the newborn.
D) All of the above are necessary to establish that the newborn has Down syndrome.
Viral genomes may be composed of
A) RNA only.
B) DNA only.
C) either RNA or DNA.
D) both RNA and DNA.
Which element is not found in a molecule of DNA?
Which is found in RNA, but NOT DNA?
Which of the following is a DNA base pair?
Although RNA is typically single-stranded, some RNA molecules, such as tRNA, have regions of base pairing. Which of the following pairings is possible?
Prior to publication of the structure of DNA by James Watson and Francis Crick, Erwin Chargaff showed that certain ratios between various nucleotides in DNA molecules. Choose the answer that most accurately reflects the ratio(s) that can be inferred from the structure of DNA and are now known as Chargaff's rules?
A) A / T = 1
B) G / C = 1
C) A + G (purines) / T + C (pyrimidines) = 1
D) All of the above are known as Chargaff's rules and can be inferred from the structure of DNA
The strands of DNA molecules can be separated by heating. It has been shown that A-T base pairs are less thermostable than G-C base pairs. Which of the following is the reason for this difference?
A) Purines are less thermostable than pyrimidines.
B) The 5' to 3' polarity of each strand stabilizes the G-C base pairs but not the A-T base pairs.
C) A-T base pairs from two hydrogen bonds whereas G-C base pairs form three hydrogen bonds.
D) Hydrogen bonds between G and C are formed faster at higher temperatures.
An Amoeba has 100 times more DNA per cell than a human. A lily bulb has 10 times more DNA per cell than a human. A rice plant has 10 times less DNA than a human per cell. A corn plant has twice as much DNA per cell than a human. These data illustrate what principle?
A) The amount of heterochromatin varies from one cell to another.
B) DNA content of plants is higher than animals because plants do photosynthesis.
C) The C-value paradox.
D) Chargaff's rules.