Studied by 67 peopleBinary Fission in prokaryotes does not require the
a. replication of DNA b. elongation of the cell c. separation of the daughter cells by septum formation d. assembly of the nuclear envelope
d
Chromatin is composed of
a. RNA and protein b. DNA and protein c. sister chromatids d. chromosomes
b
What is a nucleosome?
a. A region of the cell's nucleus that contains euchromatin b. A region of DNA wound around histone proteins c. A region of a chromosome made up of multiple loops of chromatin d. a 30-nm fiber found in chromatin
b
What is the role of cohesion proteins in cell division?
a. They organize the DNA of the chromosomes into highly condensed structures b. They hold the DNA of the sister chromatids together c. They help the cell divide into two daughter cells d. They connect microtubules and chromosomes
b
The kinetochore is a structure that functions to
a. connect the centromere to microtubules b. connect centrioles to microtubules c. aid in chromosome condensation d. aid in chromosome cohesion
a
Separation of the sister chromatids occurs during
a. prophase b. prometaphase c. anaphase d. telophase
c
Why is cytokinesis an important part of cell division?
a. it is responsible for the proper separation of genetic material b. it is responsible for the proper separation of the cytoplasmic contents c. It triggers the movement of a cell through the cell cycle d. it allows cells to halt at checkpoints
b
What steps in the cell cycle represent irreversible commitments?
a. the S/G2 phase checkpoint b. the G1/S checkpoint c. anaphase d. both b and c are correct
d
In comparing somatic cells and gametes, somatic cells are
a. diploid with half the number of chromosomes b. haploid with half the number of chromosomes c. diploid with twice the number of chromosomes d. haploid with twice the number of chromosomes
c
What are homologous chromosomes?
a. the two halves of a replicated chromosome b. two identical chromosomes from one parent c. two genetically identical chromosomes, one from each parent d. two genetically similar chromosomes, one from each parent
d
Chiasmata form between
a. between homologous chromosomes b. sister chromatids c. between replicated copies of the same chromosomes d. sex chromosomes but not autosomes
a
Crossing over involves each of the following with the exception of
a. the transfer of DNA between two nonsister chromatids b. the transfer of DNA between two sister chromatids c. the formation of a synaptonemal complex d. the alignment of homologous chromosomes
b
During anaphase I
a. sister chromatids separate and move to the poles b. homologous chromosomes move to opposite poles c. homologous chromosomes align at the middle of the cell d. all the chromosomes align independently at the middle of the cell
b
At metaphase I the kinetochores of sister chromatids are
a. attached to microtubules from the same pole b. attached to microtubules from opposite poles c. held together with cohesin proteins d. not attached to any microtubules
a
what occurs during the anaphase of meiosis II?
a. the homologous chromosomes align b. sister chromatids are pulled to opposite poles c. homologous chromosomes are pulled to opposite poles d. the haploid chromosomes line up
b
Why do retroviruses need to contain the enzyme reverse transcriptase?
A. Because host cells make DNA from RNA only in G2 of the cell cycle, and HIV infects only during G1 of the cell cycle
B. Because host cells' genomes do not contain a gene encoding an enzyme that can make DNA from RNA
C. Because HIV deletes large parts of the host cell genome upon infection, and that means there is a chance that host cell reverse transcriptase will be deleted
D. Host cells cannot make RNA from DNA
b
What is the most reasonable explanation for why a bacteriophage capable of infecting E. coli would be unable to infect a human lung epithelial cell?
a. the nature of the genetic material is different tin lung cells from that in E. coli
b. bacteriophage need the reverse transcriptase enzyme that is found only in E. coli
c. the receptors to which the bacteriophage attach on E. coli are not found on lung cells
d. the bacteriophage is too large to enter the bronchioles of the lungs
c
Why might the ability of a virus to convert a benign bacterium into a pathogen be selected for by natural selection?
a. the pathogenic virus will kill the host b. the pathogenic virus may cause disease symptoms (diarrhea, coughing) that lead to spreading of the virus c. the pathogenic virus may not respond to antibiotics d. the pathogenic virus will be more stable in the environment
b
Which of the following kinds of proteins would be least likely to be expressed during the lysogenic cycle of a temperate phage?
a. a protein to integrate the prophage into the host genome b. a protein to switch off genes for the lytic cycle of the phage c. a protein to suppress DNA replication in the host d. a protein to promote cell lysis by breaking down the cell wall of the host cell
d
Why is a drug that blocks HIV binding to one of its cell surface receptors not effective at treating influenza?
a. HIV and influenza viruses have different receptors to which they bind b. HIV and influenza viruses use different types of genetic material c. The mechanism for genome replication in HIV and in influenza viruses is different d. HIV causes a chronic infection; infection causes an acute infection
a
Why is HAART more effective than a single drug in reducing HIV levels in infected people?
a. The drugs together are more toxic to the virus than is any drug alone b. Mutations that confer resistance to several drugs are much less likely than is a mutation that confers resistance to a single drug c. the drugs work synergistically to boost the immune system d. they work together to reduce antigenic shift in the viral genome
b
The "information" contained in PrPSc must be contained in
a. the sequence of nucleotides in the PrPC gene b. the sequence of nucleotides in the PrPSc gene c. the sequence of amino acids in the PrPSc polypeptide d. the three-dimensional structure of the PrPSc protein
d
A main difference between prokaryotes and eukaryotes is that eukaryotic, but not prokaryotic, cells possess
a. membrane-bound genetic material b. a cell membrane c. cell walls d. ribosomes
a
A bacteria that obtains carbon from the atmosphere and energy from reduced inorganic compounds is best characterized as a
a. chemoorganoheterotroph b. chemoheterotroph c. chemolithoautotroph d. photolithoautotroph
c
Gram-positive and gram-negative bacteria are distinguished based on differences in their
a. cell walls; gram-positives have peptidoglycan, whereas gram-negatives have pseudo-peptidoglycan
b. plasma membranes: gram-positives have ester-linked lipids, whereas gram-negatives have ether-linked lipids
c. cell walls: gram-positives have a thick layer of peptidoglycan, whereas gram-negatives have a thin layer
d. chromosomal structure: gram-positives have circular chromosomes, whereas gram-negatives have linear chromosomes
c
Bacteria and archaebacteria may be distinguished based on
a. the type of nucleic acid used as genetic material b. cell membrane structure and chemistry c. the presence and absence of organelles d. size
b
The transfer of very specific genes from one bacterium to another by a virus is called
a. natural transformation b. generalized transduction c. specialized transduction d. conjugation
c
Tuberculosis is caused by a(n)
a. bacterium b. archaebacterium c. virus d. protist
a
During respiration, bacteria can use a greater diversity of electron ________ and ________ than can eukaryotics.
a. oxidizers; reducers b. reducers; oxidizers c. donors; reducers d. donors; acceptors
d
Which of the following structures is unique to prokaryotes?
a. pili b. flagella c. cell wall d. spores
a
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