The full chemical name of DNA is .
The protein, , is needed to lay down a segment of RNA complementary to the DNA before replication can begin.
An origin of replication generally has (how many?) replication forks.
The discontinuous lagging strand on a replication fork consists of that are later ligated together to form one strand of DNA.
The E. coli chromosome contains (how many?) origin(s) of replication?
A prokaryote lacks a membrane.
Recombination is probably always initiated by of DNA.
The strand is synthesized continuously during DNA replication.
A enzyme recognizes a specific DNA sequence and is able to cleave the DNA generating either “blunt” or “sticky” ends of the DNA.
A virus that infects bacterial cells is called a .
The genetic material of some viruses such as pi X 174 and M13 is .
The genetic material of the viruses that cause polio and AIDS is .
Topoisomerase supercoils by nicking the DNA.
In E. coli, recombination begins at sites where recBCD nicks and displaces a strand.
Which of the following is not true of DNA?
It is acidic.
It contains deoxyribose.
It is found in cell nuclei.
It contains phosphate.
It contains proteins.
The molecule of heredity is:
RNA
DNA
protein
carbohydrate
none of the above
The four subunits which compose DNA are called:
phosphodiesters
proteins
nucleotides
nucleosides
polymers
DNA is localized mainly in the
cell membrane
endoplasmic reticulum
vacuoles
chromosomes
None of the above
Each nucleotide of DNA is made up of:
a deoxyribose sugar
a nitrogenous base
a phosphate
A and B only
All of the above
The polarity of DNA synthesis is:
5' → 3'
3' → 5'
5' → 2'
2' → 5'
In the Hershey and Chase experiment designed to determine the molecule of heredity, what was radiolabeled with 35-S?
rRNA
The ratio of _____ is 1:1.
guanine to adenine
adenine to thymine
cytosine to adenine
uracil to cytosine
X-ray data showed that the spacing between repeating units along the axis of the DNA helix is:
2.0 angstroms.
3.4 angstroms.
20 angstroms.
34 angstroms.
X-ray data showed that the DNA helix undergoes one complete turn every:
________ bonds are responsible for the chemical affinity between A and T (or G and C) nucleotides.
Ionic
Covalent
Hydrogen
Electro-ionic
_______ -form DNA spirals to the right and is the major form of naturally occurring DNA molecules.
A
B
D
Y
Z
The nucleotide that is present in RNA but not DNA is:
thymine
uracil
adenine
cytosine
guanosine
DNA replication occurs through a _________process.
conservative
semiconervative
dispersive
transferal
During complementary base pairing, enzymes join the base's nucleotide to the preceding nucleotide by a __________bond.
Phosphodiester
Electrostatic
During early interphase the state of the DNA can be described as:
a single continuous linear double helix.
a double helix replicated semiconservatively.
a double helix replicated conservatively.
single-stranded DNA.
During the S phase of interphase, the state of the DNA can be described as:
a triple helix replicated semiconservatively.
The step in DNA replication in which the replication proteins open up the double helix and prepare for complementary base pairing is called:
Initiation
Elongation
Termination
Translation
Translocation
The step in DNA replication in which the proteins connect the correct sequence of nucleotides into a continuous new strand is called:
The step in DNA replication in which two replication forks moving in opposite directions may meet is called:
Intiation
The group of enzymes able to relax supercoils in DNA is called:
Primases
Helicases
Topoisomerases
Telomeres
Ligases
How many replication forks depart from an origin of replication?
one
two
three
four
The protein that progressively unwinds DNA ahead of each replication fork is called:
Primase
Helicase
Topoisomerase
Telomerase
Ligase
In eukaryotic cells, replication proceeds from ____ origin(s) of replication.
no
several
many
Eukaryotic chromosomes have evolved special structures at the ends of chromosomes to ensure the replication of the two ends of linear chromosomes. These structures are
methylases
capping proteins
ligases
telomerases
single-stranded binding proteins
Which of the following is NOT involved in ensuring the accuracy of a cell's genetic information?
redundancy
repair enzymes
precision of replication machinery
DNA polymerase proofreading mechanism
Restriction endonucleases
The process of _________ is extremely important in generating genetic diversity.
Transcription
Recombination
Transformation
Any deviation from the expected 2:2 segregation of parental alleles that results from recombination is known as:
Allelic exchange
Gene conversion
Crossing over
DNA replication
Recombination involves the breakage and reunion of DNA molecules from:
homologous nonsister chromatids
homologous sister chromatids
heterologous nonsister chromatids
heterologous sister chromatids
The nicking of DNA that initiates recombination during mitosis may be due to all but:
instruction from normal cell-cycle program
X-rays
Chemical change
Physical change
Radiation
What radiolabeled substance did Hershey and Chase use to label the protein component of the bacteriophage in their study to determine whether protein or DNA was necessary for phage production?
nitrogen
carbon
sulfur
phosphorous
iodide
If 35% of the bases in a region of the mouse genome are cytosine, what percentage in that region are adenine?
15%
20%
30%
35%
The complementary sequence of 5' AATTCGCTTA 3' is:
5' AATTCGCTTA 3'
3' AATTCGCTTA 5'
5' TAACGCTTAA 3'
5' TAAGCGAATT 3'
3' TAAGCGAATT 5'
Two strains of S. cerevisae (yeast) are crossed. One has the genotype ABC and the other abc. Five sets of the resultant tetrads are noted below. In which set did a gene conversion event occur?
abc, aBc, AbC, aBC
abc, abc, ABC, ABC
aBc, aBc, AbC, AbC
abC, abc, ABc, ABC
Abc, Abc, aBC, aBC
Recombination occurs during meiotic ________.
anaphase
interphase
prophase
metaphase
Without __________ regions on the DNA during recombination, gene conversion could not occur.
homoduplex
heteroduplex
homotriplex
heterotriplex
Occasionally, a loss of function mutation may occur in the telomerase enzyme in a cell. What is likely to be the result of this mutation on the DNA in the cell over the the course of several rounds of mitosis?
chromosome length will gradually increase
chromosome length will gradually decrease
chromosome length will stay constant
chromosomes will fail to dissociate after replication
Bacterial DNA is resistant to degradation by its own restriction enzymes through the protection of:
Methylases
Recombinases
Hershey and Chase relied on ________ to physically separate the infected bacterial cells from the phage ghosts.
radioactivity
gel filtration
ion exchange
centrifugation
Meselson and Stahl relied on equilibrium density gradient centrifugation in a _______ solution to resolve the DNA containing 14N from the DNA containing 15-N.
radiolabeled phosphate
calcium chloride
radiolabeled nitrogen
sodium acetate
cesium chloride
Match the scientist with their contribution to understanding more about DNA a. early recombination models b. transformation c. semiconservative replication d. x-ray structure of DNA e. revised recombination models f. basic structure of DNA g. DNA = molecule of heredity h. discovery of “nuclein” i. nucleotide ratios in DNA j. famous phage blender experiment
55. Watson and Crick
56. Chargaff
57. Franklin and Wilkins
58. Griffith
59. Hershey and Chase
60. Miescher
61. Meselson and Stahl
62. Holliday
63. Meselson and Radding
64. Avery, MacLeod and McCarty
Diagram Matching (Match the region or item on the diagram with the correct term from the list below)
-lagging strand
-leading strand
-origin
-RNA primer
-Okazaki fragment
-helicase
-polymerase
A phosphodiester bond joins one nucleotide together in the DNA polymer.
Prokaryotes have a circular chromosome surrounded by a nuclear membrane.
Transformation in bacteria results from the uptake of foreign DNA.
DNA is highly negatively charged throughout the molecule and therefore has no
A region of DNA 100 bp in length has the potential to be represented by 4100 unique sequences.
Viruses use only DNA as their genetic material.
Restriction enzymes are molecular weapons which cut DNA that bacteria use in their fight to protect themselves from DNA viruses.
Human DNA is replicated in a conservative manner.
In DNA replication, new DNA is produced in a continuous bi-directional fashion.
DNA topoisomerase supercoils DNA to get it out of the way of DNA polymerase.
Accuracy of replication is enhanced by the redundancy of DNA, enzymatic repair of damaged DNA and the remarkable precision of the cellular replication machinery.
A 2:2 segregation of parental alleles is known as gene conversion.
Recombination events are limited to only “hot spots” along a chromosome.
Gene conversion in which a small segment of information from one homologous chromosome transfers to the other can give rise to an unequal yield of two different alleles.
Alternative resolutions of the Holliday intermediate are responsible for whether or not crossing over or gene conversion occurs.
Genes that “travel” together from one generation to the next more often than not exhibit .
A probability test that measures “goodness of fit” between observed and predicted results is a test.
A hypothesis that predicts no linkage between genes is called the hypothesis.
Genes that can serve points of reference on a chromosome are useful as genetic markers while cytologically visible abnormalities that also make it possible to keep track of chromosomes are called markers.
The movement of chiasmata toward the end of a chromosome is called .
One percentage point of recombination, or recombination frequency, is a unit of measure called either centimorgan or .
Crossovers do not occur independently and the occurrence of one crossover reduces the likelihood of another occurring elsewhere on the chromosome this is called .
A tetrad that contains four recombinant class haploid cells is known as a ditype.
A tetrad that carries four kinds of haploid cells: two different parental and two different recombinant class spores is referred to as .
Mistakes in mitosis during development often result in organisms containing tissues of different genotypes.
The R/r and S/s genes are linked and 10 map units apart. In the cross Rs/rS rs/rs what fraction of the progeny will be RS/rs?
5%
10%
25%
40%
45%
If the map distance between genes A and B is 10 map units and the map distance between genes B and C is 25 map units, what is the map distance between genes A and C?
15 map units
35 map units
Either 15 map units or 35 map units, depending on the order of the genes
The map distance between A and C can not be predicted from this data
In Drosophila, singed bristles (sn) and cut wings (ct) are both caused by recessive, X-linked alleles. The wild type alleles (sn+ and ct+) are responsible for straight bristles and intact wings, respectively. A female homozygous for sn and ct+ is crossed to a sn+ct male. The F1 flies are interbred. The F2 males are distributed as follows: sn ct 13 sn ct+ 36 sn+ ct 39 sn+ ct+ 12 What is the map distance between sn and ct?
12 m.u.
13 m.u.
25 m.u.
50 m.u.
75 m.u.
What is the value of X2 for a test of the hypothesis that the sn and car genes are unlinked?
0.5
1.0
2.0
0.4
20
What is the p value from this test? (Pick the most accurate choice.)
p > 0.5
0.5 > p > 0.1
p < 0.1
p < 0.05
p < 0.01
Suppose the L and M genes are on the same chromosome but separated by 100 map units. What fraction of the progeny from the cross LM/lm x lm/lm would be Lm/lm?
50%
75%
100%
The pairwise map distances for four linked genes are as follows: A-B = 22 m.u., B-C = 7 m.u., C-D = 9 m.u., B-D = 2 m.u., A-D = 20 m.u., A-C = 29 m.u. What is the order of these four genes?
ABCD
ADBC
ABDC
BADC
CADB
The zipper-like connection between paired homologs in early prophase is known as a:
spindle fiber
synaptic junction
synaptomnemal complex
chiasma
The measured distance between genes D and E in a two point test cross is 50 map units. What does this mean in physical terms?
D and E are on different pairs of chromosomes.
D and E are linked and exactly 50 map units apart.
D and E are linked and at least 50 map units apart.
either A or B
either A or C
Suppose an individual is heterozygous for a pair of alleles (e.g. A/a). Under what conditions would a crossover in a somatic cell of this individual lead to a clone of cells homozygous for a? (Pick the most precise answer.)
The crossover would have to occur between the A locus and the centromere and involve two homologous (non-sister) chromatids.
The crossover would have to occur between the A locus and the end of the chromosome and involve two homologous (non-sister) chromatids.
The crossover would have to occur on the same chromosome arm as the A locus and involve two homologous (non-sister) chromatids.
The crossover would have to occur on the same chromosome as the A locus and involve two homologous (non-sister) chromatids.
The crossover would have to occur between the A locus and the centromere and involve two sister chromatids (not homologous) chromatids.
Suppose an individual is heterozygous for two linked pairs of alleles on the same chromosome arm, Ab/aB such that the A locus is closer to the centromere than the B locus. Under what conditions would a crossover in a somatic cell generate a twin spot, i.e. two adjacent clones of cells, one clone homozygous for a and the other clone homozygous for b?
The crossover would have to occur between the A locus and the centromere locus and involve two homologous (non-sister) chromatids.
The crossover would have to occur between the A locus and the B locus locus and involve two homologous (non-sister) chromatids.
The crossover would have to occur between the B locus and the end of the chromosome locus and involve two homologous (non-sister) chromatids.
A double crossover would have to occur, with one crossover between the A locus and the centromere and a second crossover between the A and B loci locus and both crossovers would have to involve two homologous (non-sister) chromatids.
No crossover in a somatic cell could generate a twin spot.
What happens physically during the process of crossing over?
Two homologous chromatids break and rejoin at random sites along the chromosome.
The genetic information on one chromatid is replaced by copying genetic information from a homologous chromatid without there being any physical exchange between the chromosomes.
Two homologous chromatids break and rejoin at precisely the same site along the chromosome so that there is no loss or gain of material on either product.
It is not known what occurs during crossing over.
Here is a list of events during meiosis I. It is not in the correct order. A) Homologous chromosomes are roughly aligned but not physically linked. B) Homologous chromosomes segregate to opposite poles. C) Homologous chromosomes are linked by synaptonemal complexes. D) Homologous chromosomes are linked by chiasmata. E) Chromosomes replicate. What is the correct order of these events?
ACDBE
AECDB
EACDB
EADCB
CDABE
Some of the larger human chromosomes typically contain multiple chiasmata during meiotic prophase. If you were to carefully study the distribution of these chiasmata, what would you find?
Chiasmata are randomly distributed along chromosomes.
All chromosome pairs have the same number of chiasmata.
A single chromosome pair always has the same number of chiasmata in every meiotic cell.
Chiasmata are spaced along a chromosome arm more regularly than would be expected by chance.
Chiasmata are spaced more irregularly along a chromosome arm than would be expected by chance.
Recombination due to crossing over occurs only rarely in mitosis.
When considering the chi-square test, a p-value of 0.05 is often considered significant but is actually an arbitrary assignment of significance.
Chiasmata are structures of cross over between sister chromatids of homologous chromosomes.
Chiasmata can be seen through a light microscope and are sites of recombination.
Three-point crosses are more tedious and less accurate than two-point crosses.
Chromosomal interference is not uniform and may significantly vary within a region of a single chromosome.
Genetic mapping distance calculated for a chromosome is directly related to physical distance along that chromosome.
Genes chained together by linkage relationships are known collectively as a linkage group.
Ascospores are haploid cells that can germinate, replicate by mitosis, and survive as haploid individuals.
The Hardy-Weinberg equilibrium principle yields which of the following conclusions?
If the allele frequencies in a population are given by p and q, the genotype frequencies are given by p2, 2 pq and q2.
The allele frequencies in a population will not change over time.
If the allele frequencies in a population are given by p and q, the genotype frequencies are given by p2 and q2. d. The first and third answers are correct.
The first and second choices are correct.
The HIV epidemic is unlikely to lead to an increase in the CCR5 delta-32 allele over the short term because ___________________.
In populations with high selection pressure, the allele frequency is low.
the allele is recessive and deleterious.
in populations with a high frequency of the allele, selection pressure is relatively low.
Over the long term, selection favoring the rare phenotype in a polymorphic population (i.e., negative frequency dependent selection), will __________ genetic diversity in the population.
decrease
increase
maintain
Which of these statements is true for underdominance?
Allele frequencies will tend to move towards fixation or loss.
Allele frequencies will tend to move toward a stable equilibrium.
Allele frequencies may initially hover at an unstable equilibrium, but will eventually change.
When selection acts against a recessive allele that is initially at high frequency in a population, ____________________.
the frequency of the allele will stay high for a long time, then decline slowly.
the allele declines in frequency until it is eliminated.
the frequency of the allele will be unchanged;
the population will remain in Hardy-Weinberg equilibrium. the frequency of the allele will decline rapidly, and then stabilize at very low frequency.
When selection favors heterozygotes over homozygotes, ____________________.
both alleles are maintained at a frequency different from that predicted by Hardy-Weinberg principles based on the strength of selection against the recessive allele.
the selective advantage enjoyed by the deleterious allele in the heterozygote exactly
genetic diversity in the population can be maintained indefinitely, in spite of selection acting against the allele. balances the selective disadvantage suffered by homozygous recessive individuals.
The first two choices are both correct.
The first three choices are correct.
When selection favors homozygotes over heterozygotes ____________________.
genetic variation among populations will decline.
the most common outcome will be that the most common allele will become fixed (will increase to a frequency of 1) in the population.
both alleles are maintained in the population at frequencies different from those predicted by Hardy-Weinberg principles.
the genetic variation within a population is maintained over time
Pier and his colleagues have suggested that cystic fibrosis is maintained at relatively high levels in people of European ancestry because of heterozygote superiority; specifically, he proposposes that heterozygotes are more resistant to typhoid fever than are the dominant homozygotes. Evidence in favor of this hypothesis includes which of the following findings?
The mutation rate for new loss-of-function mutations in the CFTR gene is too low for the prevalence of the disease to be explained by mutation/selection balance.
Pier and his colleagues have found, in 11 European countries, an association between the severity of typhoid fever outbreaks and the frequency of the delta-F508 allele (the most common loss-of-function mutation) a generation later.
Pier et al. engineered cells homozygous for functional CFTR alleles, homozygous for a common loss-of-function allele, and heterozygous for the two. The loss-of-function homozygotes were virtually impervious to invasion by typhoid fever-causing bacteria; heterozygotes were more vulnerable, but accumulated 86% fewer bacteria than did the dominant homozygotes.
All of the choices above are correct.
Salmonella typhi bacteria manipulate their host cells, causing them to express more CFTR protein on their membranes.
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