test 3 Flashcards
(169 cards)
1
Q
A mutation that changes the codon UAA to the codon UAG in a mammalian cell line is called a(n)
A
synonymous mutation
2
Q
A mutation changes a codon from AAA (encoding lysine) to AGA (encoding arginine) in yeast, but no mutant phenotype is detected when the mutant strain is plated and grown on minimal or complete medium. This type of mutation is called
A
missense
3
Q
A mutation does not affect the length of a gene but results in an abnormally short protein. The mutation is most likely of a type called
A
nonsense
4
Q
A small (one-base-pair) insertion in the middle of the coding region of a gene will cause a
A
frameshift mutation
5
Q
A point mutation in a gene’s promoter will most likely cause the production of
A
reduced amounts of mRNA and protein
6
Q
The rare enol form of thymine pairs with guanine. If a thymine enolization occurs during replication, what would be the mutational event?
A
TA to CG
7
Q
After mutagen treatment, a molecule of 2-aminopurine (an adenine analogue) incorporates into DNA. During replication, the 2-AP protonates. The mutational event caused by this will be
A
AT to GC
8
Q
During mutagenic treatment with nitrous acid, an adenine deaminates to form hypoxanthine, which bonds like guanine. The mutational event would be
A
AT to GC
9
Q
Which mutagen causes transitions (usually GC to AT) by adding an alkyl group to a base (usually G), thus altering its pairing properties?
A
ethymethanesulfonate (EMS)
10
Q
Which mutagen causes AT-to-GC transitions by acting as a base analog for adenine? Hint: It is unstable and readily undergoes tautomeric shifts. Its imino form pairs with C rather than G.
A
2 aminopurine
11
Q
Which of the following scientists discovered the Ac and Ds transposable elements in maize?
A
babara McClintock
12
Q
A corn plant is homozygous for a mutant allele that results in no pigment in the seed (i.e., white). The mutant is caused by Ds insertion that often exits late in seed development, when there is an active Ac element in the genome. The seeds of this plant will be
A
white with small spots of pigment
13
Q
Which of the following features do bacterial and corn transposons not have in common?
A
both may carry drug resistance genes in natural population
14
Q
an autonomous element
A
requires no other elements for its mobility
15
Q
Retrotransposons move via an intermediate that is
A
single-stranded RNA
16
Q
LINEs differ from retrotransposons in that LINEs do NOT
A
contain LTRs
17
Q
What percentage of the human genome is derived from transposable elements?
A
50%
18
Q
A particular hybrid species is defined as 3n = 12. It is discovered that at meiosis, pairing is always univalent + bivalent (never trivalent) in this species. How many bivalents will be present in prophase of meiosis I?
A
4
19
Q
For autosomes in diploid organisms, the aneuploid 2n + 1 is
A
trisomic
20
Q
for autosomes in diploid organisms, the aneuploid 2n-1 is
A
monosomic
21
Q
For autosomes in diploid organisms, the aneuploid 2n – 2 is
A
nullisomic
22
Q
A man is found to be karyotypically 47, XYY. The presence of an extra Y chromosome most likely results from
A
Nondisjunction in a paternal meiocyte at meiosis II.
23
Q
A hybrid allotetraploid species (2n = 60) was backcrossed to one of the suspected parents (2n = 30). When the F1 underwent meiosis, the prophase chromosome configuration was examined. If the guess about the suspected parent was correct, what would the chromosome configuration look like?
A
15 pairs and 15 singles
24
Q
The red fox has 17 pairs of large, long chromosomes. The arctic fox has 26 pairs of smaller shorter chromosomes. What do you expect to be the chromosome number in somatic tissues of a red fox/arctic fox hybrid?
A
43
25
spontaneous mutations
"background" mutation rate. Influence phenotype occurs at a very low rate
26
induced mutations
caused by muta gens= agents that increase the rate of mutations. can occur at a high rate.
27
men are
4 times more likely to have mutations.
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point mutations
mutations that map to a single and specific point(usually a single base pair or a few base pairs)
29
Indels
insertion or deletions
30
depurination
occurs spontaneously all the time
31
deamination
Removal of an amino group from a base. This most commonly occurs at cytosine.
32
transposable genetic elements
DNA sequences can move within the genome through an enzyme-driven process called transposition.
33
insertion inactivation
a transposable element can cause a mutation if it inserts into a wild-type allele and disrupts its function
34
dissociation (Ds) element
is the location of chromosome breakage.
35
Activator (Ac) element
Ds can not cause chromosome breakage without this second element.
36
McClintock concluded that the unstable mutant alleles
were cause by insertion of Ds into the C locus to produce a kernel lacking pigmentation
37
why does the insertion of Ds into the C locus cause the colorless phenotype?
the insertion mutates the allele and disrupts its original function of producing blue pigment
38
transposition requires what enzyme?
transposase
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autonomous transposable elements
carry a transposase gene and all DNA sequences needed to carry out transposition
40
non-autonomous transposable elements
have no transposase gene and may lack the sequences need for transposition
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IS (insertion sequence) elements
are simple transposable elements containing only the genes and sequences needed for autonomous transposition.
42
Bacteria has how many types of transposons
two
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composite transposons
have a central region of several kb containing one or more functional genes.
44
simple transposons
are flanked bby very short IR sequences of less than 50bp
45
DNA transposons
are transposed through conservative or replicative transposition (DNA cut and paste)
46
retrotransposons
are transcribed then reverse transcriptase produces a double-stranded DNA copy of the element, which is then inserted into the genome. (copy and paste)
47
what virus is a retrovirus
HIV
48
what is the ploidy of strawberry
4n
49
what is the ploidy of bread wheat?
6n
50
what is the ploidy of seedless watermelon
3n
51
Meisosis in even numbered eukaryotes
works because of the need to pair with homologs
52
Meiosis in odd number
fails because chromosomes will not pair with a homolog
53
Autopolypoidy
occurs when organisms have more then two sets of chromosomes from the same species
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allopolyploidy
when organism contain two or more sets of chromosomes that are form different species.
53
why does triploidy not work?
because gametes with one or two of each chromosome will produce inviable offspring.
53
monosomic
missing one copy of one chormosome (2n-1)
54
trisomic
an additional copy of one chromosome (2n+)
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nullisomic
no copies of a particular chromosome (2n-2)
56
translocations
Chromosomal breakage followed by reattachment of the broken segment to a non homologous chromosome.
57
where does heritable genetic variation come from?
mutation
58
microsatellite markers
- high mutation rate, multiple alleles at the same locus, tandem repeats, highly abundant in genomes
59
what is a population?
a group of interbreeding organisms
60
what is a gene pool
the collection of genes and alleles found in the members of a population
61
Hardy-Weinburg equilibrium
serves as a model to calculate the frequencies of alleles and genotypes in a population that is infinitely large, practices random mating, and does not experience evolutionary change. alleles and genotype frequencies remain constant.
62
p^2=
A1xA1
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2pq=
2(A1xA2)
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q^2=
A2xA2
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mutation _____ genetic diversity
increases
66
migration _____ genetic diversity
increases
67
genetic drift _____ genetic diversity
decreases
68
the effect of genetic drift is stringer in _____ population
small
69
what does natural selection favor?
reproductive fitness
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relative fitness
high reproductive success
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directional natural selection
one phenotype has a higher relative fitness than other phenotypes. increase the frequency of the favored allele over the others.
72
directional selection ____ genetic diversity
decreases
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balanced polymorphism
allele frequencies are maintained by selection against either homozygote
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inbreeding
is mating between related individuals
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inbreeding ____ genetic diversity
decreases
76
discontinuous variation
displayed by phenotypes of single-gene traits
77
continuous variation
what polygenic and multifactorial traits are controlled by many genes and show
78
how many genetic variants (SNPs) affect human height
10000
79
major gene
several alleles that strongly influence something
80
modifier genes
influence genes to a lesser degree.
81
additive genes
a gene in which there are neither dominant nor recessive alleles, although gradations may exist between extremes.
82
additive trait
more alleles associated with a particular trait an individual possesses, the greater the expression of that trait.
83
multiple gene hypothesis
in the early 1900s, geneticists began to investigate the idea that segregation of alleles of multiple genes played a role in phenotypic variation.
84
no gene-environment interaction
each genotype corresponds to a discrete phenotype
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moderate gene-environment interaction
minor overlaps between phenotypes in the F2
86
substantial gene-environment interaction
wide phenotypic ranges and significant overlap
87
threshold traits
There is constant variation of phenotypes, but the phenotypes can still be divided into distinct categories, either affected or unaffected.
88
frequency distribution
shows the proportion of individuals for each category
89
varience (s^2)
is a measure of the spread of distribution around the mean
90
variance equation
s^2=E(xi-x)^2/df
91
standard deviation
expresses deviation from the mean in the same units as the scale of measurement for the sample s=√s^2
92
phenotypic variance
Vp=Vg+Ve
93
genetic variance
Vg, is the proportion of phenotypic variance due to genotypes differences.
94
environmental variance
Ve
95
in highly inbred mice populations where all individuals are homozygous for alleles controlling a trait, what is the genetic variance for this trait?
Vg is 0
96
we keep a population of maize in the same lab environment and measure their heights. what is the environmental variance
Ve is 0
97
additive variance
Va, derives from the added effects of all alleles contributing to the trait
98
dominance variance
Vd, results from dominance relationships in which heterozygous individuals are not intermediate between the two homozygous states
99
interactive variance
Vi, derives from epistatic interactions between alleles contributing to a trait
100
concept of heritability
was developed to help measure the proportion of phenotypic variation that is due to genetic variation
101
broad sense of heritability
H^2=Vg/Vp, estimates the proportion of phenotypic variation that is due to total genetic variation
101
Narrow sense of heritability h^2
h^2=Va/Vp, estimates the proportion of phenotypic variation that is due to additive genetic variability
102
selection differential
S, the difference between the means of the whole population and the breeding population
103
response to selection
R=Sxh^2, depends on the extent to which the difference between the population mean and the mean of the mating individuals can be passed on to progeny
104
h^2
=R/S
105
An animal breeder asks for your advice about which of a number of traits could most effectively be selected for his herd. which would you most correctly suggest?
a high Va relative to Vp
106
which of the following is most typical of a case of quantitative inheritance
continuous variation in phenotypes
107
A high variance indicates that
the variation among the values is high.
108
Which of the following statements is/are a central assumption of the multifactorial inheritance hypothesis?
Several loci are associated with the trait.
109
The amount of milk produced per day by a cow is an example of a
continuous trait
110
A large number of genetically identical tomato plants are grown in a greenhouse. The mean height in this plant population is 84 cm, and the standard deviation is 2.5 cm. The variation in height within this population is most likely due to
differences in the plants' microenvironment.
111
When all of the variation in a population is due to environmental sources and there is no genetic variation, broad-sense heritability (H2) is
zero and all of the phenotypic variability is due to environment.
112
A quantitative geneticist measures the broad-sense heritability for bill length in an isolated population of ducks to be 0.75. This result suggests that
in the population tested, 75% of the variance in bill length is due to genetic differences among individuals.
113
Narrow-sense heritability (h2) is a quantification of the proportion of total variance due to
additive genetic variance
114
what is a species
a collection of organisms that can interbreed and produce fertile offspring
115
what is a population
a group of organisms that live in a defined area and can interbreed
116
what is phenotypic variation
the variability in phenotypes that exists in a population
117
what is selection pressure
impact on a trait from a population's environment from human activity or from other organisms.
118
what is fitness
the ability to survive to reproductive age, find a mate, and produce offspring
119
survival of the fittest
term that suggests that organism best adjusted to their environment are the most successful in surviving and reproducing
120
what is adaptation
modification of an organism or its parts that make it more fit
121
what is biological evolution
change of allele frequency in populations
122
does the gene that encodes lactase present in juvenile mammals disappear when they grow older?
No, the cell just stops expressing that gene by stoping transcription of that DNA.
123
missense muation
nonsynonymous but changes amino acid
124
silent mutation
synonymous mutation but does not change amino acid
125
nonsense mutation
forms new stop codon
126
keto and enols form pairs with
different nucleotides
127
depurination
removal of purine from apurinic site an then replaced with other purine
128
deamination
removal of an amino group from a base
129
what are the effects of the muattions induced by mutagens
they are harmful
130
what do inversions do?
they supress the production of recombinant chromosomes because they are not viable if crossover occurs in the inversion loop.
131
larger inversion =
lower fertility and higher probability of crossing over in the loop.
132
inversion loops result in
major chromosomal deletions after recombination in an inversion heterozygote
133
as long as genes or regulatory regions are away from the breaking point
the inversions and translocations will likely not have phenotypic consequences (except for reduced fertility)
134
Which of the following processes will increase genetic variation within populations?
mutation
135
Which of the following are requirements for evolution by natural selection?
differential survival and reproduction, heritability of phenotypic variation, and variation in phenotype
136
Which of these principles of evolution, as described by Darwin's theory, is correctly matched with its role in evolution?
Principle of variation: Variation in morphology, physiology, and behavior must be present in a population for selection to occur.
137
Which of the following is/are NOT a principle of Darwinian evolution?
Darwinian evolution fully describes where all living things come from.
138
Which of the following reduce heterozygosity?
directional selection
139
how might a single base insertion into the second codon of the coding sequence of a gene affect the amino acid sequence of a protein encoded by the gene?
the amino acid sequence would be altered.
140
which type of mutation converts a nucleotide to an alternative structure with same composition but a slightly different placement of rare, less stable hydrogen bonds that cause base-pair mismatch?
tautomeric shift
141
An intercalating agent such as aflatoxin is more likely to cause which type of mutation?
frameshift
142
which of the following statements is true of non-homologous end joining?
it is a double-strand repair pathway, and it is error prone
143
nucleotide base repair
using undamaged strand as a template to repair the damaged strand.
144
in an allopolyploid organism, what is true regarding the fertility of interspecies hybrids?
chromosome doubling and nondisjunction in gametocytes can lead to homologous chromosome pairing, disjunction, and fertile hybrids.
145
heterozygous carriers of chromosome inversions or translocations____.
may or may not exhibit phenotypic abnormalities, and may be infertile due to complications during meiosis
146
A region of a chromosome spanning the centromere is broken and reattached in the reverse direction. This is an example of which type of chromosomal defect?
pericentric inversion
147
a chromosome has broken, and a piece of one chromosome is translocated to a non-homologous chromosome. this is an example of what type of chromosomal alteration?
unbalanced translocation
148
Alu1 is an example of which type of transposable element commonly found in the genome of humans?
SINE elements
149
LINE elements
a group of non-LTR (long terminal repeat) retrotransposons that are widespread in the genome of many eukaryotes.
150
SINE elements
a class of retrotransposons, DNA elements that amplify themselves throughout eukaryotic genomes, often through RNA intermediates.
151
transition mutations
purine to purine or pyrimidine to pyrimidiyne
152
transverion muations
purine to pyrimidine
153
what is a major cause of aneuploidy?
nondisjunction
154
aneuploidy
an abnormality in the number of chromosomes in a cell due to loss or duplication. an example is down syndrome
155
what is an example of not a transition mutation
A to c
156
what ploidy level does 3n=36 represent?
triploid
157
human males introduce more point mutations (base substitutions) than females into the human gene pool. Is this true or false
true
158
humans have how many pairs of chromosomes
23 pairs
159
synthesis dependent strand anneling
this mechanism is initiated if DNA has already been synthesized. it is an error free repair mechanism
160
Chromosomal aberrations occur at a lower frequency than spontaneous mutations in humans. this statement is true or false?
false
161
down syndrome is caused by
an insertion
162
what is a close approximation of spontaneous mutation rate in humans?
10x10^-9
163
which agent of population genetics refers to chance fluctations of allele frequences resulting from sampling error and is more prominent in small, isolated populations?
gene drift
164
which of the following best predicts the response of a trait to artificial selection?
h^2
165
A region of a chromosome **NOT** spanning the centromere is broken and reattached in the reverse direction. This is an example of which type of chromosomal defect?
paracentric inversion
