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Genetics Review
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
A cell that remains entirely flexible in its
developmental possibilities is said to be
A. differentiated. B. determined.
C. totipotent.
D. genomically equivalent. E. epigenetic.
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
The pedigree shows the
transmission of a trait
in a particular family.
The trait is most likely
A. mitochondrial.
B. autosomal recessive.
C. sex-linked dominant.
D. sex-linked recessive.
E. autosomal dominant.
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.
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 that
A. 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.
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
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
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
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 selfpollinate. 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
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
This protein is produced by a regulatory gene:
A. operon
B. inducer
C. promoter
D. repressor
E. corepressor
Two characters that appear in a 9:3:3:1 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.
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. 2:1 male to female B. 1:2 male to female
C. 1:1 male to female D. 4:3 male to female
E. 3:1 male to female
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
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
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.
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 that
A. 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.
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.
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
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. 1
C. 2/4
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
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
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
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
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
Once transcribed, eukaryotic mRNA
typically undergoes substantial alteration
that includes
A. 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.
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.
When translating secretory or membrane proteins,
ribosomes are directed to the ER membrane by
A. 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.
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.
Mendel accounted for the observation that traits which had
disappeared in the F1 generation reappeared in the F2 generation
by proposing that
A. 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.
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
The fact that plants can be cloned from somatic
cells demonstrates that
A. 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.
Within a cell, the amount of protein made
using a given mRNA molecule depends
partly on
A. 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.
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.
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, 3
C. 5, 4, 3, 2, 1
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
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
gene
A. 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.
Use the following for the next question
A peptide has the sequence
NH2-phe-pro-lys-gly-phe-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
Muscle cells differ from nerve cells
mainly because they
A. express different genes.
B. contain different genes.
C. use different genetic codes.
D. have unique ribosomes.
E. have different chromosomes.
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.
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
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.
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.
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
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
Steroid hormones produce their effects in cells by
A. 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.
The lactose operon is likely to be transcribed
when
A. 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.
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. MRI
B. Ultrasound imaging
C. Amniocentesis
D. Fetoscopy
E. X-ray
A cross between homozygous purple-flowered
and homozygous white-flowered pea plants
results in offspring with purple flowers. This
demonstrates
A. the blending model of genetics.
B. true-breeding.
C. dominance.
D. a dihybrid cross.
E. the mistakes made by Mendel.
A mutation that inactivates the regulatory gene of a
repressible operon in an E. coli cell would result in
A. 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.
This can inhibit transcription by blocking the
binding of positively acting transcription factors
to the DNA:
A. enhancer
B. promoter
C. activator
D. repressor
E. terminator
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.
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
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
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
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
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
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. ttRr–dwarf and pink
B. ttrr–dwarf and white
C. TtRr–tall and red
D. TtRr–tall and pink
E. TTRR–tall and red