Genetics Review

1
Genetics Review
2
Huntington's disease is a dominant condition with
late age of onset in humans. If one parent has
the disease, what is the probability that his or
her child will have the disease? A. 1 B. 3/4
C. 1/2 D. 1/4 E. 0
3
A cell that remains entirely flexible in its
developmental possibilities is said to
beA. differentiated. B. determined.
C. totipotent. D. genomically equivalent.
E. epigenetic.
4
The frequency of Down syndrome in the human
population is most closely correlated with which
of the following? A. Frequency of new meiosis
B. Average of the ages of mother and father
C. Age of the mother D. Age of the father
E. Exposure of pregnant women to
environmental pollutants
5
The pedigree shows the transmission of a trait
in a particular family. The trait is most
likelyA. mitochondrial. B. autosomal
recessive. C. sex-linked dominant.
D. sex-linked recessive. E. autosomal
dominant.
6
Sturtevant provided genetic evidence for the
existence of four pairs of chromosomes in
Drosophila in which of these ways?A. There are
four major functional classes of genes in
Drosophila. B. Drosophila genes cluster into
four distinct groups of linked genes. C. The
overall number of genes in Drosophila is a
multiple of four. D. The entire Drosophila
genome has approximately 400 map units.
E. Drosophila genes have, on average, four
different alleles.
7
A mutant bacterial cell has a defective aminoacyl
synthetase that attaches a lysine to tRNAs with
the anticodon AAA instead of a phenylalanine. The
consequence of this for the cell will be
thatA. none of the proteins in the cell will
contain phenylalanine. B. proteins in the cell
will include lysine instead of phenylalanine at
amino acid positions specified by the codon UUU.
C. the cell will compensate for the defect by
attaching phenylalanine to tRNAs with
lysine-specifying anticodons. D. the ribosome
will skip a codon every time a UUU is
encountered. E. None of the above will occur
the cell will recognize the error and destroy the
tRNA.
8
A few decades ago, Knudsen and colleagues
proposed a theory that, for a normal cell to
become a cancer cell, a minimum of two genetic
changes had to occur in that cell. Knudsen was
studying retinoblastoma, a childhood cancer of
the eye. If there are two children born from the
same parents, and child one inherits a
predisposition to retinoblastoma (one of the
mutations) and child two does not, but both
children develop the retinoblastoma, which of the
following would you expect?A. an earlier age of
onset in child one B. a history of exposure to
mutagens in child one but not in child two
C. a more severe cancer in child one
D. increased levels of apoptosis in both
children E. decreased levels of DNA repair in
child one
9
From the following list, which is the first event
in translation in eukaryotes?A. elongation of
the polypeptide B. base pairing of activated
methionine-tRNA to AUG of the messenger RNA
C. the larger ribosomal subunit binds to smaller
ribosomal subunits D. covalent bonding between
the first two amino acids E. the small subunit
of the ribosome recognizes and attaches to the 5'
cap of mRNA
10
A man who is an achondroplastic dwarf with normal
vision marries a color-blind woman of normal
height. The man's father was six feet tall, and
both the woman's parents were of average height.
Achondroplastic dwarfism is autosomal dominant,
and red-green color blindness is X-linked
recessive. What proportion of their sons would be
color-blind and of normal height?A. All
B. Three out of four C. Half D. One out of
four
11
In a particular plant, leaf color is controlled
by gene locus D. Plants with at least one allele
D have dark green leaves, and plants with the
homozygous recessive dd genotype have light green
leaves. A true-breeding dark-leaved plant is
crossed with a light-leaved one, and the
offspring is allowed to self-pollinate. The
predicted outcome of the is diagrammed in the
Punnett square, where 1, 2, 3, and 4 represent
the genotypes corresponding to each box within
the square. Which of the boxes correspond to
plants with a heterozygous genotype?A. 1 B. 1
and 2 C. 1, 2, and 3 D. 2 and 3 E. 2, 3,
and 4
12
In a particular plant, leaf color is controlled
by gene locus D. Plants with at least one allele
D have dark green leaves, and plants with the
homozygous recessive dd genotype have light green
leaves. A true-breeding dark-leaved plant is
crossed with a light-leaved one, and the
offspring is allowed to self-pollinate. The
predicted outcome of the is diagrammed in the
Punnett square, where 1, 2, 3, and 4 represent
the genotypes corresponding to each box within
the square.Which of the boxes marked 1-4
correspond to plants with dark leaves?A. 1 only
B. 1 and 2 C. 2 and 3 D. 4 only E. 1,
2, and 3
13
This protein is produced by a regulatory
geneA. operon B. inducer C. promoter
D. repressor E. corepressor
14
Two characters that appear in a 9331 ratio in
the generation should have which of the
following properties?A. Each of the traits is
controlled by single genes. B. The genes
controlling the characters obey the law of
independent assortment. C. Each of the genes
controlling the characters has two alleles.
D. Four genes are involved. E. Sixteen
different phenotypes are possible.
15
In birds, sex is determined by a ZW chromosome
scheme. Males are ZZ and females are ZW. A
recessive lethal allele that causes death of the
embryo is sometimes present on the Z chromosome
in pigeons. What would be the sex ratio in the
offspring of a cross between a male that is
heterozygous for the lethal allele and a normal
female?A. 21 male to female B. 12 male to
female C. 11 male to female D. 43 male to
female E. 31 male to female
16
Women with Turner syndrome have a genotype
characterized as which of the following?A. aabb
B. Mental retardation and short arms C. A
karyotype of 45, X D. A karyotype of 47, XXX
E. A deletion of the Y chromosome
17
A scientist discovers a DNA-based test for the
allele of a particular gene. This and only this
allele, if homozygous, produces an effect that
results in death at or about the time of birth.
Of the following, which is the best use of this
discovery?A. To screen all newborns of an
at-risk population B. To design a test for
identifying heterozygous carriers of the allele
C. To introduce a normal allele into deficient
newborns D. To follow the segregation of the
allele during meiosis E. To test school-age
children for the disorder
18
Suppose an experimenter becomes proficient with a
technique that allows her to move DNA sequences
within a prokaryotic genome. If she moves the
promoter for the lac operon to the region between
the beta galactosidase gene and the permease
gene, which of the following would be
likely?A. Three structural genes will no longer
be expressed. B. RNA polymerase will no longer
transcribe permease. C. The operon will no
longer be inducible. D. Beta galactosidase
will be produced. E. The cell will continue to
metabolize but more slowly.
19
A transcription unit that is 8,000 nucleotides
long may use 1,200 nucleotides to make a protein
consisting of approximately 400 amino acids. This
is best explained by the fact thatA. many
noncoding stretches of nucleotides are present in
mRNA. B. there is redundancy and ambiguity in
the genetic code. C. many nucleotides are
needed to code for each amino acid.
D. nucleotides break off and are lost during the
transcription process. E. there are
termination exons near the beginning of mRNA.
20
Which of the following statements about the DNA
in one of your brain cells is true?A. Most of
the DNA codes for protein. B. The majority of
genes are likely to be transcribed. C. Each
gene lies immediately adjacent to an enhancer.
D. Many genes are grouped into operon-like
clusters. E. It is the same as the DNA in one
of your heart cells.
21
What is considered to be the first evidence of
differentiation in the cells of an
embryo?A. cell division B. the occurrence of
mRNAs for the production of tissue-specific
proteins C. determination D. changes in the
size and shape of the cell E. changes resulting
from induction
22
Some of members of a family exhibit the dominant
trait, wooly hair. Affected individuals are
indicated by an open square or circle. What is
the probability that individual III-1 is
Ww?A. 3/4 D. 2/3 B. 1/4 E. 1C. 2/4
23
A transfer RNA (1) attached to the amino acid
lysine enters the ribosome. The lysine binds to
the growing polypeptide on the other tRNA (2) in
the ribosome already. When the ribosome reaches a
stop codon on the mRNA, no corresponding tRNA
enters the A site. If the translation reaction
were to be experimentally stopped at this point,
which of the following would you be able to
isolate?A. an assembled ribosome with a
polypeptide attached to the tRNA in the P site
B. separated ribosomal subunits, a polypeptide,
and free tRNA C. an assembled ribosome with a
separated polypeptide D. separated ribosomal
subunits with a polypeptide attached to the tRNA
E. a cell with fewer ribosomes
24
The process of translation, whether in
prokaryotes or eukaryotes, requires tRNAs, amino
acids, ribosomal subunits, and which of the
following?A. polypeptide factors plus ATP
B. polypeptide factors plus GTP C. polymerases
plus GTP D. SRP plus chaperones E. signal
peptides plus release factor
25
Which of the following statements describes
proto-oncogenes?A. They can code for proteins
associated with cell growth. B. They are
introduced to a cell initially by retroviruses.
C. They are produced by somatic mutations
induced by carcinogenic substances. D. Their
normal function is to suppress tumor growth
E. They are underexpressed in cancer cells
26
Gene expression in Archaea differs from that in
other prokaryotes. It shares features with which
of the following?A. eubacteria only
B. eukaryotes only C. protists only
D. fungi only E. bacteria and eukaryotes
27
A Barr body is normally found in the nucleus of
which kind of human cell?A. Unfertilized egg
cells only B. Sperm cells only C. Somatic
cells of a female only D. Somatic cells of a
male only E. Both male and female somatic
cells
28
Once transcribed, eukaryotic mRNA typically
undergoes substantial alteration that
includesA. union with ribosomes. B. fusion
into circular forms known as plasmids.
C. linkage to histone molecules. D. excision
of introns. E. fusion with other newly
transcribed mRNA.
29
According to Beadle and Tatum's hypothesis, how
many genes are necessary for this pathway?A. 0
B. 1 C. 2 D. 3 E. It cannot be
determined from the pathway.
30
When translating secretory or membrane proteins,
ribosomes are directed to the ER membrane byA. a
specific characteristic of the ribosome itself,
which distinguishes free ribosomes from bound
ribosomes. B. a signal-recognition particle
that brings ribosomes to a receptor protein in
the ER membrane. C. moving through a
specialized channel of the nucleus. D. a
chemical signal given off by the ER. E. a
signal sequence of RNA that precedes the start
codon of the message.
31
What do gap genes, pair-rule genes, segment
polarity genes, and homeotic genes all have in
common?A. Their products act as transcription
factors. B. They have no counterparts in
animals other than Drosophila. C. Their
products are all synthesized prior to
fertilization. D. They act independently of
other positional information. E. They
apparently can be activated and inactivated at
any time of the fly's life.
32
Mendel accounted for the observation that traits
which had disappeared in the F1 generation
reappeared in the F2 generation by proposing
thatA. new mutations were frequently generated
in the F2 progeny, "reinventing" traits that had
been lost in the F1. B. the mechanism
controlling the appearance of traits was
different between the F1 and the F2 plants.
C. traits can be dominant or recessive, and the
recessive traits were obscured by the dominant
ones in the F1. D. the traits were lost in the
F1 due to blending of the parental traits.
E. members of the F1 generation had only one
allele for each character, but members of the F2
had two alleles for each character.
33
If glucose is available in the environment of E.
coli, the cell responds with very low
concentration of cAMP. When the cAMP increases in
concentration, it binds to CAP. Which of the
following would you expect would then be a
measurable effect?A. decreased concentration of
the lac enzymes B. increased concentration of
the trp enzymes C. decreased binding of the
RNA polymerase to sugar metabolism-related
promoters D. decreased concentration of
alternative sugars in the cell E. increased
concentrations of sugars such as arabinose in the
cell
34
The fact that plants can be cloned from somatic
cells demonstrates thatA. differentiated cells
retain all the genes of the zygote. B. genes
are lost during differentiation. C. the
differentiated state is normally very unstable.
D. differentiated cells contain masked mRNA.
E. differentiation does not occur in plants.
35
Within a cell, the amount of protein made using a
given mRNA molecule depends partly onA. the
degree of DNA methylation. B. the rate at which
the mRNA is degraded. C. the presence of
certain transcription factors. D. the number of
introns present in the mRNA. E. the types of
ribosomes present in the cytoplasm.
36
Which of the following statements describes
genomic imprinting?A. It explains cases in which
the gender of the parent from whom an allele is
inherited affects the expression of that allele.
B. It is greatest in females because of the
larger maternal contribution of cytoplasm.
C. It may explain the transmission of Duchenne
muscular dystrophy. D. It involves an
irreversible alteration in the DNA sequence of
imprinted genes.
37
Choose the answer that has these events of
protein synthesis in the proper sequence.1. An
aminoacyl-tRNA binds to the A site.2. A peptide
bond forms between the new amino acid and a
polypeptide chain.3. tRNA leaves the P site, and
the P site remains vacant.4. A small ribosomal
subunit binds with mRNA.5. tRNA translocates to
the P site.A. 1, 3, 2, 4, 5 D. 4, 1, 3, 2, 5
B. 4, 1, 2, 5, 3 E. 2, 4, 5, 1, 3C. 5, 4,
3, 2, 1
38
Abnormal chromosomes are frequent in malignant
tumors. Errors such as translocations may place a
gene in close proximity to different control
regions. Which of the following might then occur
to make the cancer worse?A. An increase in
non-disjunction B. Expression of inappropriate
gene products C. A decrease in mitotic
frequency D. Death of the cancer cells in the
tumor E. Sensitivity of the immune system
39
Absence of bicoid mRNA from a Drosophila egg
leads to the absence of anterior larval body
parts and mirror-image duplication of posterior
parts. This is evidence that the product of the
bicoid geneA. is transcribed in the early
embryo. B. normally leads to formation of tail
structures. C. normally leads to formation of
head structures. D. is a protein present in
all head structures. E. leads to programmed
cell death.
40
Use the following for the next question
41
A peptide has the sequence NH2-phe-pro-lys-gly-ph
e-pro-COOH. Which of the following sequences in
the coding strand of the DNA could code for this
peptide?A. 3' UUU-CCC-AAA-GGG-UUU-CCC B. 3'
AUG-AAA-GGG-TTT-CCC-AAA-GGG C. 5'
TTT-CCC-AAA-GGG-TTT-CCC D. 5'
GGG-AAA-TTT-AAA-CCC-ACT-GGG E. 5'
ACT-TAC-CAT-AAA-CAT-TAC-UGA
42
Muscle cells differ from nerve cells mainly
because theyA. express different genes.
B. contain different genes. C. use different
genetic codes. D. have unique ribosomes.
E. have different chromosomes.
43
If a Drosophila female has a homozygous mutation
for a maternal effect gene,A. she will not
develop past the early embryonic stage. B. all
of her offspring will show the mutant phenotype,
regardless of their genotype. C. only her male
offspring will show the mutant phenotype.
D. her offspring will show the mutant phenotype
only if they are also homozygous for the
mutation. E. only her female offspring will
show the mutant phenotype.
44
New combinations of linked genes are due to which
of the following?A. Nondisjunction
B. Crossing over C. Independent assortment
D. Mixing of sperm and egg E. Deletions
45
The bicoid gene product is normally localized to
the anterior end of the embryo. If large amounts
of the product were injected into the posterior
end as well, which of the following would
occur?A. The embryo would grow to an unusually
large size. B. The embryo would grow extra
wings and legs. C. The embryo would probably
show no anterior development and die.
D. Anterior structures would form in both sides
of the embryo. E. The embryo would develop
normally.
46
Which of the following statements are true about
protein synthesis in prokaryotes?A. Extensive
RNA processing is required before prokaryotic
transcripts can be translated. B. Translation
can begin while transcription is still in
progress. C. Prokaryotic cells have
complicated mechanisms for targeting proteins to
the appropriate cellular organelles.
D. Translation requires antibiotic activity.
E. Unlike eukaryotes, prokaryotes require no
initiation or elongation factors.
47
Which of the following help(s) to stabilize mRNA
by inhibiting its degradation?A. TATA box
B. spliceosomes C. 5' cap and poly (A) tail
D. introns E. RNA polymerase
48
When does translation begin in prokaryotic
cells?A. after a transcription initiation
complex has been formed B. as soon as
transcription has begun C. after the 5' caps
are converted to mRNA D. once the pre-mRNA has
been converted to mRNA E. as soon as the DNA
introns are removed from the template
49
Steroid hormones produce their effects in cells
byA. activating key enzymes in metabolic
pathways. B. activating translation of certain
mRNAs. C. promoting the degradation of
specific mRNAs. D. binding to intracellular
receptors and promoting transcription of specific
genes. E. promoting the formation of looped
domains in certain regions of DNA.
50
The lactose operon is likely to be transcribed
whenA. there is more glucose in the cell than
lactose. B. the cyclic AMP levels are low.
C. there is glucose but no lactose in the cell.
D. the cyclic AMP and lactose levels are both
high within the cell. E. the cAMP level is
high and the lactose level is low.
51
An obstetrician knows that one of her patients is
a pregnant woman whose fetus is at risk for a
serious disorder that is detectable biochemically
in fetal cells. The obstetrician would most
reasonably offer which of the following
procedures to her patient?A.  MRIB. Ultrasound
imaging C. Amniocentesis D. Fetoscopy
E. X-ray
52
A cross between homozygous purple-flowered and
homozygous white-flowered pea plants results in
offspring with purple flowers. This
demonstratesA. the blending model of genetics.
B. true-breeding. C. dominance. D. a
dihybrid cross. E. the mistakes made by
Mendel.
53
A mutation that inactivates the regulatory gene
of a repressible operon in an E. coli cell would
result inA. continuous transcription of the
structural gene controlled by that regulator.
B. complete inhibition of transcription of the
structural gene controlled by that regulator.
C. irreversible binding of the repressor to the
operator. D. inactivation of RNA polymerase by
alteration of its active site. E. continuous
translation of the mRNA because of alteration of
its structure.
54
This can inhibit transcription by blocking the
binding of positively acting transcription
factors to the DNAA. enhancer B. promoter
C. activator D. repressor E. terminator
55
One of two major forms of a human condition
called neurofibromatosis (NF 1) is inherited as a
dominant, although it may be either mildly to
very severely expressed. If a young child is the
first in her family to be diagnosed, which of the
following is the best explanation?A. The mother
carries the gene but does not express it at all.
B. One of the parents has very mild expression
of the gene. C. The condition skipped a
generation in the family. D. The child has a
different allele of the gene than the parents.
56
An ideal procedure for fetal testing in humans
would have which of the following
features?A. Lowest risk procedure that would
provide the most reliable information B. The
procedure that can test for the greatest number
of traits at once C. A procedure that provides
a 3D image of the fetus D. The procedure that
can be performed at the earliest time in the
pregnancy E. A procedure that could test for
the carrier status of the fetus
57
In the structural organization of many eukaryotic
genes, individual exons may be related to which
of the following?A. the sequence of the intron
that immediately precedes each exon B. the
number of polypeptides making up the functional
protein C. the various domains of the
polypeptide product D. the number of
restriction enzyme cutting sites E. the number
of start sites for transcription
58
A nonreciprocal crossover causes which of the
following products?A. Deletion only
B. Duplication only C. Nondisjunction
D. Deletion and duplication E. Duplication
and nondisjunction
59
What is a ribozyme?A. an enzyme that uses RNA as
a substrate B. an RNA with enzymatic activity
C. an enzyme that catalyzes the association
between the large and small ribosomal subunits
D. an enzyme that synthesizes RNA as part of the
transcription process E. an enzyme that
synthesizes RNA primers during DNA replication
60
Correns described that the inheritance of
variegated color on the leaves of certain plants
was determined by the maternal parent only. What
phenomenon does this describe?A. Mitochondrial
inheritance B. Chloroplast inheritance
C. Genomic imprinting D. Infectious
inheritance E. Sex-linkage
61
Tallness (T) in snapdragons is dominant to
dwarfness (t), while red (R) flower color is
dominant to white (r). The heterozygous condition
results in pink (Rr) flower color. A dwarf, red
snapdragon is crossed with a plant homozygous for
tallness and white flowers. What are the genotype
and phenotype of the individuals?A. ttRrdwarf
and pink B. ttrrdwarf and white
C. TtRrtall and red D. TtRrtall and pink
E. TTRRtall and red