7246577
Descripción
Test por Engela Zalmy, actualizado hace más de 1 año
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Creado por Engela Zalmy
hace casi 8 años
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|
Pregunta 1
Pregunta
The full chemical name of DNA is [blank_start]deoxyribonucleic acid[blank_end] .
Respuesta
-
deoxyribonucleic acid
Pregunta 2
Pregunta
The protein, [blank_start]primase[blank_end], is needed to lay down a segment of RNA complementary to the DNA before replication can begin.
Respuesta
-
primase
Pregunta 3
Pregunta
An origin of replication generally has [blank_start]two[blank_end] (how many?) replication forks.
Respuesta
-
two
Pregunta 4
Pregunta
The discontinuous lagging strand on a replication fork consists of [blank_start]Okazaki fragments[blank_end] that are later ligated together to form one strand of DNA.
Respuesta
-
Okazaki fragments
Pregunta 5
Pregunta
The E. coli chromosome contains [blank_start]one[blank_end] (how many?) origin(s) of replication?
Respuesta
-
one
Pregunta 6
Pregunta
A prokaryote lacks a [blank_start]nuclear[blank_end] membrane.
Respuesta
-
nuclear
Pregunta 7
Pregunta
Recombination is probably always initiated by [blank_start]nicking[blank_end] of DNA.
Respuesta
-
nicking
Pregunta 8
Pregunta
The [blank_start]leading[blank_end] strand is synthesized continuously during DNA replication.
Respuesta
-
leading
Pregunta 9
Pregunta
A [blank_start]restriction[blank_end] enzyme recognizes a specific DNA sequence and is able to cleave the DNA generating either “blunt” or “sticky” ends of the DNA.
Respuesta
-
restriction
Pregunta 10
Pregunta
A virus that infects bacterial cells is called a [blank_start]bacteriophage[blank_end].
Respuesta
-
bacteriophage
Pregunta 11
Pregunta
The genetic material of some viruses such as pi X 174 and M13 is [blank_start]single-stranded DNA[blank_end].
Respuesta
-
single-stranded DNA
Pregunta 12
Pregunta
The genetic material of the viruses that cause polio and AIDS is [blank_start]RNA[blank_end] .
Respuesta
-
RNA
Pregunta 13
Pregunta
Topoisomerase [blank_start]relaxes[blank_end] supercoils by nicking the DNA.
Respuesta
-
relaxes
Pregunta 14
Pregunta
In E. coli, recombination begins at [blank_start]chi[blank_end] sites where recBCD nicks and displaces a strand.
Respuesta
-
chi
Pregunta 15
Pregunta
Which of the following is not true of DNA?
Respuesta
-
It is acidic.
-
It contains deoxyribose.
-
It is found in cell nuclei.
-
It contains phosphate.
-
It contains proteins.
Pregunta 16
Pregunta
The molecule of heredity is:
Respuesta
-
RNA
-
DNA
-
protein
-
carbohydrate
-
none of the above
Pregunta 17
Pregunta
The four subunits which compose DNA are called:
Respuesta
-
phosphodiesters
-
proteins
-
nucleotides
-
nucleosides
-
polymers
Pregunta 18
Pregunta
DNA is localized mainly in the
Respuesta
-
cell membrane
-
endoplasmic reticulum
-
vacuoles
-
chromosomes
-
None of the above
Pregunta 19
Pregunta
Each nucleotide of DNA is made up of:
Respuesta
-
a deoxyribose sugar
-
a nitrogenous base
-
a phosphate
-
A and B only
-
All of the above
Pregunta 20
Pregunta
The polarity of DNA synthesis is:
Respuesta
-
5' → 3'
-
3' → 5'
-
5' → 2'
-
2' → 5'
-
none of the above
Pregunta 21
Pregunta
In the Hershey and Chase experiment designed to determine the molecule of heredity, what was radiolabeled with 35-S?
Respuesta
-
protein
-
DNA
-
RNA
-
rRNA
-
none of the above
Pregunta 22
Pregunta
The ratio of _____ is 1:1.
Respuesta
-
guanine to adenine
-
adenine to thymine
-
cytosine to adenine
-
uracil to cytosine
-
none of the above
Pregunta 23
Pregunta
X-ray data showed that the spacing between repeating units along the axis of the DNA helix is:
Respuesta
-
2.0 angstroms.
-
3.4 angstroms.
-
20 angstroms.
-
34 angstroms.
-
none of the above
Pregunta 24
Pregunta
X-ray data showed that the DNA helix undergoes one complete turn every:
Respuesta
-
2.0 angstroms.
-
3.4 angstroms.
-
20 angstroms.
-
34 angstroms.
-
none of the above
Pregunta 25
Pregunta
________ bonds are responsible for the chemical affinity between A and T (or G and C) nucleotides.
Respuesta
-
Ionic
-
Covalent
-
Hydrogen
-
Electro-ionic
-
none of the above
Pregunta 26
Pregunta
_______ -form DNA spirals to the right and is the major form of naturally occurring DNA molecules.
Respuesta
-
A
-
B
-
D
-
Y
-
Z
Pregunta 27
Pregunta
The nucleotide that is present in RNA but not DNA is:
Respuesta
-
thymine
-
uracil
-
adenine
-
cytosine
-
guanosine
Pregunta 28
Pregunta
DNA replication occurs through a _________process.
Respuesta
-
conservative
-
semiconervative
-
dispersive
-
transferal
-
none of the above
Pregunta 29
Pregunta
During complementary base pairing, enzymes join the base's nucleotide to the preceding nucleotide by a __________bond.
Respuesta
-
Hydrogen
-
Ionic
-
Phosphodiester
-
Electrostatic
-
None of the above
Pregunta 30
Pregunta
During early interphase the state of the DNA can be described as:
Respuesta
-
a single continuous linear double helix.
-
a double helix replicated semiconservatively.
-
a double helix replicated conservatively.
-
single-stranded DNA.
-
None of the above
Pregunta 31
Pregunta
During the S phase of interphase, the state of the DNA can be described as:
Respuesta
-
a single continuous linear double helix.
-
a double helix replicated semiconservatively.
-
a double helix replicated conservatively.
-
a triple helix replicated semiconservatively.
-
None of the above
Pregunta 32
Pregunta
The step in DNA replication in which the replication proteins open up the double helix and prepare for complementary base pairing is called:
Respuesta
-
Initiation
-
Elongation
-
Termination
-
Translation
-
Translocation
Pregunta 33
Pregunta
The step in DNA replication in which the proteins connect the correct sequence of nucleotides into a continuous new strand is called:
Respuesta
-
Initiation
-
Elongation
-
Termination
-
Translation
-
Translocation
Pregunta 34
Pregunta
The step in DNA replication in which two replication forks moving in opposite directions may meet is called:
Respuesta
-
Intiation
-
Elongation
-
Termination
-
Translation
-
Translocation
Pregunta 35
Pregunta
The group of enzymes able to relax supercoils in DNA is called:
Respuesta
-
Primases
-
Helicases
-
Topoisomerases
-
Telomeres
-
Ligases
Pregunta 36
Pregunta
How many replication forks depart from an origin of replication?
Respuesta
-
one
-
two
-
three
-
four
-
none of the above
Pregunta 37
Pregunta
The protein that progressively unwinds DNA ahead of each replication fork is called:
Respuesta
-
Primase
-
Helicase
-
Topoisomerase
-
Telomerase
-
Ligase
Pregunta 38
Pregunta
In eukaryotic cells, replication proceeds from ____ origin(s) of replication.
Respuesta
-
no
-
one
-
two
-
several
-
many
Pregunta 39
Pregunta
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
Respuesta
-
methylases
-
capping proteins
-
ligases
-
telomerases
-
single-stranded binding proteins
Pregunta 40
Pregunta
Which of the following is NOT involved in ensuring the accuracy of a cell's genetic information?
Respuesta
-
redundancy
-
repair enzymes
-
precision of replication machinery
-
DNA polymerase proofreading mechanism
-
Restriction endonucleases
Pregunta 41
Pregunta
The process of _________ is extremely important in generating genetic diversity.
Respuesta
-
Translation
-
Transcription
-
Recombination
-
Transformation
-
None of the above
Pregunta 42
Pregunta
Any deviation from the expected 2:2 segregation of parental alleles that results from recombination is known as:
Respuesta
-
Allelic exchange
-
Gene conversion
-
Crossing over
-
Recombination
-
DNA replication
Pregunta 43
Pregunta
Recombination involves the breakage and reunion of DNA molecules from:
Respuesta
-
homologous nonsister chromatids
-
homologous sister chromatids
-
heterologous nonsister chromatids
-
heterologous sister chromatids
-
None of the above
Pregunta 44
Pregunta
The nicking of DNA that initiates recombination during mitosis may be due to all but:
Respuesta
-
instruction from normal cell-cycle program
-
X-rays
-
Chemical change
-
Physical change
-
Radiation
Pregunta 45
Pregunta
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?
Respuesta
-
nitrogen
-
carbon
-
sulfur
-
phosphorous
-
iodide
Pregunta 46
Pregunta
If 35% of the bases in a region of the mouse genome are cytosine, what percentage in that region are adenine?
Respuesta
-
15%
-
20%
-
30%
-
35%
-
none of the above
Pregunta 47
Pregunta
The complementary sequence of 5' AATTCGCTTA 3' is:
Respuesta
-
5' AATTCGCTTA 3'
-
3' AATTCGCTTA 5'
-
5' TAACGCTTAA 3'
-
5' TAAGCGAATT 3'
-
3' TAAGCGAATT 5'
Pregunta 48
Pregunta
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?
Respuesta
-
abc, aBc, AbC, aBC
-
abc, abc, ABC, ABC
-
aBc, aBc, AbC, AbC
-
abC, abc, ABc, ABC
-
Abc, Abc, aBC, aBC
Pregunta 49
Pregunta
Recombination occurs during meiotic ________.
Respuesta
-
anaphase
-
interphase
-
prophase
-
metaphase
-
none of the above
Pregunta 50
Pregunta
Without __________ regions on the DNA during recombination, gene conversion could not occur.
Respuesta
-
homoduplex
-
heteroduplex
-
homotriplex
-
heterotriplex
-
none of the above
Pregunta 51
Pregunta
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?
Respuesta
-
chromosome length will gradually increase
-
chromosome length will gradually decrease
-
chromosome length will stay constant
-
chromosomes will fail to dissociate after replication
-
none of the above
Pregunta 52
Pregunta
Bacterial DNA is resistant to degradation by its own restriction enzymes through the protection of:
Respuesta
-
Methylases
-
Recombinases
-
Topoisomerases
-
Ligases
-
Primases
Pregunta 53
Pregunta
Hershey and Chase relied on ________ to physically separate the infected bacterial cells from the phage ghosts.
Respuesta
-
radioactivity
-
gel filtration
-
ion exchange
-
centrifugation
-
none of the above
Pregunta 54
Pregunta
Meselson and Stahl relied on equilibrium density gradient centrifugation in a _______ solution to resolve the DNA containing 14N from the DNA containing 15-N.
Respuesta
-
radiolabeled phosphate
-
calcium chloride
-
radiolabeled nitrogen
-
sodium acetate
-
cesium chloride
Pregunta 55
Pregunta
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. [blank_start]f[blank_end] Watson and Crick
56. [blank_start]i[blank_end] Chargaff
57. [blank_start]d[blank_end] Franklin and Wilkins
58. [blank_start]b[blank_end] Griffith
59. [blank_start]j[blank_end] Hershey and Chase
60. [blank_start]h[blank_end] Miescher
61. [blank_start]c[blank_end] Meselson and Stahl
62. [blank_start]a[blank_end] Holliday
63. [blank_start]e[blank_end] Meselson and Radding
64. [blank_start]g[blank_end] Avery, MacLeod and McCarty
Respuesta
-
f
-
i
-
d
-
b
-
j
-
h
-
c
-
a
-
e
-
g
Pregunta 56
Pregunta
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
Respuesta
-
leading strand
-
Okazaki fragment
-
RNA primer
-
helicase
-
polymerase
-
origin
-
lagging strand
Pregunta 57
Pregunta
A phosphodiester bond joins one nucleotide together in the DNA polymer.
Respuesta
- True
- False
Pregunta 58
Pregunta
Prokaryotes have a circular chromosome surrounded by a nuclear membrane.
Respuesta
- True
- False
Pregunta 59
Pregunta
Transformation in bacteria results from the uptake of foreign DNA.
Respuesta
- True
- False
Pregunta 60
Pregunta
DNA is highly negatively charged throughout the molecule and therefore has no
Respuesta
- True
- False
Pregunta 61
Pregunta
A region of DNA 100 bp in length has the potential to be represented by 4100 unique sequences.
Respuesta
- True
- False
Pregunta 62
Pregunta
Viruses use only DNA as their genetic material.
Respuesta
- True
- False
Pregunta 63
Pregunta
Restriction enzymes are molecular weapons which cut DNA that bacteria use in their fight to protect themselves from DNA viruses.
Respuesta
- True
- False
Pregunta 64
Pregunta
Human DNA is replicated in a conservative manner.
Respuesta
- True
- False
Pregunta 65
Pregunta
In DNA replication, new DNA is produced in a continuous bi-directional fashion.
Respuesta
- True
- False
Pregunta 66
Pregunta
DNA topoisomerase supercoils DNA to get it out of the way of DNA polymerase.
Respuesta
- True
- False
Pregunta 67
Pregunta
Accuracy of replication is enhanced by the redundancy of DNA, enzymatic repair of damaged DNA and the remarkable precision of the cellular replication machinery.
Respuesta
- True
- False
Pregunta 68
Pregunta
A 2:2 segregation of parental alleles is known as gene conversion.
Respuesta
- True
- False
Pregunta 69
Pregunta
Recombination events are limited to only “hot spots” along a chromosome.
Respuesta
- True
- False
Pregunta 70
Pregunta
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.
Respuesta
- True
- False
Pregunta 71
Pregunta
Alternative resolutions of the Holliday intermediate are responsible for whether or not crossing over or gene conversion occurs.
Respuesta
- True
- False
Pregunta 72
Pregunta
Genes that “travel” together from one generation to the next more often than not exhibit [blank_start]genetic linkage[blank_end] .
Respuesta
-
genetic linkage
Pregunta 73
Pregunta
A probability test that measures “goodness of fit” between observed and predicted results is a [blank_start]chi squared[blank_end] test.
Respuesta
-
chi squared
Pregunta 74
Pregunta
A hypothesis that predicts no linkage between genes is called the [blank_start]null[blank_end] hypothesis.
Respuesta
-
null
Pregunta 75
Pregunta
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 [blank_start]physical[blank_end] markers.
Respuesta
-
physical
Pregunta 76
Pregunta
The movement of chiasmata toward the end of a chromosome is called [blank_start]terminalization[blank_end] .
Respuesta
-
terminalization
Pregunta 77
Pregunta
One percentage point of recombination, or recombination frequency, is a unit of measure called either centimorgan or [blank_start]map unit[blank_end] .
Respuesta
-
map unit
Pregunta 78
Pregunta
Crossovers do not occur independently and the occurrence of one crossover reduces the likelihood of another occurring elsewhere on the chromosome this is called [blank_start]chromosomal interference[blank_end] .
Respuesta
-
chromosomal interference
Pregunta 79
Pregunta
A tetrad that contains four recombinant class haploid cells is known as a [blank_start]non-parental[blank_end] ditype.
Respuesta
-
non-parental
Pregunta 80
Pregunta
A tetrad that carries four kinds of haploid cells: two different parental and two different recombinant class spores is referred to as [blank_start]tetratype[blank_end].
Respuesta
-
tetratype
Pregunta 81
Pregunta
Mistakes in mitosis during development often result in [blank_start]mosaic[blank_end] organisms containing tissues of different genotypes.
Respuesta
-
mosaic
Pregunta 82
Pregunta
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?
Respuesta
-
5%
-
10%
-
25%
-
40%
-
45%
Pregunta 83
Pregunta
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?
Respuesta
-
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
Pregunta 84
Pregunta
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?
Respuesta
-
12 m.u.
-
13 m.u.
-
25 m.u.
-
50 m.u.
-
75 m.u.
Pregunta 85
Pregunta
What is the value of X2 for a test of the hypothesis that the sn and car genes are unlinked?
Respuesta
-
0.5
-
1.0
-
2.0
-
0.4
-
20
Pregunta 86
Pregunta
What is the p value from this test? (Pick the most accurate choice.)
Respuesta
-
p > 0.5
-
0.5 > p > 0.1
-
p < 0.1
-
p < 0.05
-
p < 0.01
Pregunta 87
Pregunta
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?
Respuesta
-
10%
-
25%
-
50%
-
75%
-
100%
Pregunta 88
Pregunta
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?
Respuesta
-
ABCD
-
ADBC
-
ABDC
-
BADC
-
CADB
Pregunta 89
Pregunta
The zipper-like connection between paired homologs in early prophase is known as a:
Respuesta
-
spindle fiber
-
synaptic junction
-
synaptomnemal complex
-
chiasma
-
none of the above
Pregunta 90
Pregunta
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?
Respuesta
-
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
Pregunta 91
Pregunta
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.)
Respuesta
-
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.
Pregunta 92
Pregunta
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?
Respuesta
-
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.
Pregunta 93
Pregunta
What happens physically during the process of crossing over?
Respuesta
-
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.
Pregunta 94
Pregunta
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?
Respuesta
-
ACDBE
-
AECDB
-
EACDB
-
EADCB
-
CDABE
Pregunta 95
Pregunta
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?
Respuesta
-
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.
Pregunta 96
Pregunta
Recombination due to crossing over occurs only rarely in mitosis.
Respuesta
- True
- False
Pregunta 97
Pregunta
When considering the chi-square test, a p-value of 0.05 is often considered significant but is actually an arbitrary assignment of significance.
Respuesta
- True
- False
Pregunta 98
Pregunta
Chiasmata are structures of cross over between sister chromatids of homologous chromosomes.
Respuesta
- True
- False
Pregunta 99
Pregunta
Chiasmata can be seen through a light microscope and are sites of recombination.
Respuesta
- True
- False
Pregunta 100
Pregunta
Three-point crosses are more tedious and less accurate than two-point crosses.
Respuesta
- True
- False
Pregunta 101
Pregunta
Chromosomal interference is not uniform and may significantly vary within a region of a single chromosome.
Respuesta
- True
- False
Pregunta 102
Pregunta
Genetic mapping distance calculated for a chromosome is directly related to physical distance along that chromosome.
Respuesta
- True
- False
Pregunta 103
Pregunta
Genes chained together by linkage relationships are known collectively as a linkage group.
Respuesta
- True
- False
Pregunta 104
Pregunta
Ascospores are haploid cells that can germinate, replicate by mitosis, and survive as haploid individuals.
Respuesta
- True
- False
Pregunta 105
Pregunta
The Hardy-Weinberg equilibrium principle yields which of the following conclusions?
Respuesta
-
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.
Pregunta 106
Pregunta
The HIV epidemic is unlikely to lead to an increase in the CCR5 delta-32 allele over the short term because ___________________.
Respuesta
-
In populations with high selection pressure, the allele frequency is low.
-
the allele is recessive and deleterious.
-
The first and second choices are correct.
-
in populations with a high frequency of the allele, selection pressure is relatively low.
Pregunta 107
Pregunta
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.
Respuesta
-
decrease
-
increase
-
maintain
Pregunta 108
Pregunta
Which of these statements is true for underdominance?
Respuesta
-
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.
Pregunta 109
Pregunta
When selection acts against a recessive allele that is initially at high frequency in a population, ____________________.
Respuesta
-
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.
Pregunta 110
Pregunta
When selection favors heterozygotes over homozygotes, ____________________.
Respuesta
-
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.
Pregunta 111
Pregunta
When selection favors homozygotes over heterozygotes ____________________.
Respuesta
-
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
Pregunta 112
Pregunta
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?
Respuesta
-
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.
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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.
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Salmonella typhi bacteria manipulate their host cells, causing them to express more CFTR protein on their membranes.
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