d
1) Pea plants were particularly well suited for use in Mendel's breeding experiments for all of the following reasons
except that
A) peas show easily observed variations in a number of characters, such as pea shape and flower color.
B) it is possible to c
c
A plant with purple flowers is allowed to self-pollinate. Generation after generation, it produces purple flowers.
This is an example of
A) hybridization.
B) incomplete dominance.
C) true-breeding.
D) the law of segregation.
E) polygenetics.
d
Which of the following statements about Mendel's breeding experiments is correct?
A) None of the parental (P) plants were true-breeding.
B) All of the F2 progeny showed a phenotype that was intermediate between the two parental (P) phenotypes.
C) Half of
c
What is the difference between a monohybrid cross and a dihybrid cross?
A) A monohybrid cross involves a single parent, whereas a dihybrid cross involves two parents.
B) A monohybrid cross produces a single progeny, whereas a dihybrid cross produces two p
c
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
a
The F1 offspring of Mendel's classic pea cross always looked like one of the two parental varieties because
A) one allele was completely dominant over another.
B) each allele affected phenotypic expression.
C) the traits blended together during fertilizat
b
What was the most significant conclusion that Gregor Mendel drew from his experiments with pea plants?
A) There is considerable genetic variation in garden peas.
B) Traits are inherited in discrete units, and are not the results of "blending."
C) Recessiv
e
Which of the following is (are) true for alleles?
A) They can be identical or different for any given gene in a somatic cell.
B) They can be dominant or recessive.
C) They can represent alternative forms of a gene.
D) Only A and B are correct.
E) A, B, an
b
9) What is genetic cross between an individual showing a dominant phenotype (but of unknown genotype) and a
homozygous recessive individual called?
A) a self-cross
B) a testcross
C) a hybrid cross
D) an F1 cross
E) a dihybrid cross
b
How many unique gametes could be produced through independent assortment by an individual with the
genotype AaBbCCDdEE?
A) 4
B) 8
C) 16
D) 32
E) 64
d
Two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. This suggests
A) that the parents were true-breeding for contrasting traits.
B) incomplete dominance.
C) that a blending of traits has occurred.
D) that the parents we
e
Two characters that appear in a 9:3:3:1 ratio in the F2 generation should have which of the following
properties?
A) Each of the characters is controlled by a single gene.
B) The genes controlling the characters obey the law of independent assortment.
C)
b
A 9:3:3:1 phenotypic ratio is characteristic of which of the following?
A) a monohybrid cross
B) a dihybrid cross
C) a trihybrid cross
D) linked genes
E) both A and D
a
A sexually reproducing animal has two unlinked genes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?
A) HT
B) Hh
C) HhTt
D) T
b
It was important that Mendel examined not just the F1 generation in his breeding experiments, but the F2
generation as well, because
A) he obtained very few F1 progeny, making statistical analysis difficult.
B) parental traits that were not observed in th
d
When crossing a homozygous recessive with a heterozygote, what is the chance of getting an offspring with the
homozygous recessive phenotype?
A) 0%
B) 25%
C) 50%
D) 75%
E) 100%
b
P = purple, pp = white. The offspring of a cross between two heterozygous purple-flowering plants (Pp � Pp)
results in
A) all purple-flowered plants.
B) purple-flowered plants and white-flowered plants.
C) two types of white-flowered plants: PP and Pp.
D)
c
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.
a
What are Punnett squares used for?
A) predicting the result of genetic crosses between organisms of known genotypes
B) determining the DNA sequence of a given gene
C) identifying the gene locus where allelic variations are possible
D) testing for the pres
e
Which of the following is false, regarding the law of segregation?
A) It states that each of two alleles for a given trait segregate into different gametes.
B) It can be explained by the segregation of homologous chromosomes during meiosis.
C) It can acco
d
The fact that all seven of the pea plant traits studied by Mendel obeyed the principle of independent assortment
means that
A) none of the traits obeyed the law of segregation.
B) the diploid number of chromosomes in the pea plants was 7.
C) all of the ge
d
Black fur in mice (B) is dominant to brown fur (b). Short tails (T) are dominant to long tails (t). What fraction of
the progeny of the cross BbTt � BBtt will have black fur and long tails?
A) 1/16
B) 3/16
C) 3/8
D) 1/2
E) 9/16
c
In certain plants, tall is dominant to short. If a heterozygous plant is crossed with a homozygous tall plant, what
is the probability that the offspring will be short?
A) 1/2
B) 1/4
C) 0
D) 1
E) 1/6
d
A couple has three children, all of whom have brown eyes and blond hair. Both parents are homozygous for
brown eyes (BB), but one is a blond (rr) and the other is a redhead (Rr). What is the probability that their next child
will be a brown-eyed redhead?
b
Two true-breeding stocks of pea plants are crossed. One parent has red, axial flowers and the other has white,
terminal flowers; all F1 individuals have red, axial flowers. If 1,000 F2 offspring resulted from the cross,
approximately how many of them woul
e
In a cross AaBbCc � AaBbCc, what is the probability of producing the genotype AABBCC?
A) 1/4
B) 1/8
C) 1/16
D) 1/32
E) 1/64
c
Given the parents AABBCc � AabbCc, assume simple dominance and independent assortment. What proportion
of the progeny will be expected to phenotypically resemble the first parent?
A) 1/4
B) 1/8
C) 3/4
D) 3/8
E) 1
c
A 1:2:1 phenotypic ratio in the F2 generation of a monohybrid cross is a sign of
A) complete dominance.
B) multiple alleles.
C) incomplete dominance.
D) polygenic inheritance.
E) pleiotropy.
d
A tall plant is crossed with a short plant, and the progeny are all intermediate in size between the two parental plants.
This could be an example of
A) incomplete dominance.
B) polygenic inheritance.
C) complete dominance.
D) A and B
E) B and C
b
A tall plant is crossed with a short plant, and the progeny are all intermediate in size between the two parental plants.
If the intermediate F1 progeny were allowed to self-pollinate, and the F2 progeny were also intermediate in
size, but following a nor
a
A tall plant is crossed with a short plant, and the progeny are all intermediate in size between the two parental plants.
If the intermediate F1 progeny were allowed to self-pollinate, and 25% of the F2 progeny were tall, 50% were
intermediate in size, an
e
A tall plant is crossed with a short plant, and the progeny are all intermediate in size between the two parental plants.
In snapdragons, heterozygotes have pink flowers, whereas homozygotes have red or white flowers. When plants
with red flowers are cros
d
Tallness (T) 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 a
c
Skin color in a fish is inherited via a single gene with four different alleles. How many different types of
gametes would be possible in this system?
A) 1
B) 2
C) 4
D) 8
E) 16
b
in cattle, roan coat color (mixed red and white hairs) occurs in the heterozygous (Rr) offspring of red (RR) and
white (rr) homozygotes. Which of the following crosses would produce offspring in the ratio of
1 red:2 roan:1 white?
A) red � white
B) roan �
d
Feather color in budgies is determined by two different genes Y and B. YYBB, YyBB, or YYBb is green; yyBB or yyBb
is blue; YYbb or Yybb is yellow; and yybb is white.
A blue budgie is crossed with a white budgie. Which of the following results is not possi
c
Feather color in budgies is determined by two different genes Y and B. YYBB, YyBB, or YYBb is green; yyBB or yyBb
is blue; YYbb or Yybb is yellow; and yybb is white.
Two blue budgies were crossed. Over the years, they produced 22 offspring, 5 of which wer
d
A woman who has blood type A, has a daughter who is type O positive and a son who is type B negative. Rh positive is a simple dominant trait over Rh negative.
Which of the following is a possible genotype for the son?
A) IBIB
B) IBIA
C) ii
D) IBi
E) IAIA
d
A woman who has blood type A, has a daughter who is type O positive and a son who is type B negative. Rh positive is a simple dominant trait over Rh negative.
Which of the following is a possible genotype for the mother?
A) IAIA
B) IBIB
C) ii
D) IAi
E) IA
c
A woman who has blood type A, has a daughter who is type O positive and a son who is type B negative. Rh positive is a simple dominant trait over Rh negative.
Which of the following is a possible phenotype for the father?
A) A
B) O
C) B
D) AB
E) impossibl
d
A woman who has blood type A, has a daughter who is type O positive and a son who is type B negative. Rh positive is a simple dominant trait over Rh negative.
Which of the following is the probable genotype for the mother?
A) IAIARR
B) IAIARr
C) IAirr
D)
c
A woman who has blood type A, has a daughter who is type O positive and a son who is type B negative. Rh positive is a simple dominant trait over Rh negative.
Which of the following is a possible phenotype of the father?
A) A negative
B) O negative
C) B p
pleiotropy
the ability of a single gene to have multiple phenotypic effects
multiple alleles
the ABO blood group system
incomplete dominance
the phenotype of the heterozygote differs from the phenotypes of both homozygotes
pleiotropy
cystic fibrosis affects the lungs, the pancreas, the digestive system, and other organs, resulting in symptoms ranging from breathing difficulties to recurrent infections
e
Which of the following is an example of polygenic inheritance?
A) pink flowers in snapdragons
B) the ABO blood groups in humans
C) Huntington's disease in humans
D) white and purple flower color in peas
E) skin pigmentation in humans
a
Hydrangea plants of the same genotype are planted in a large flower garden. Some of the plants produce blue
flowers and others pink flowers. This can be best explained by
A) environmental factors such as soil pH.
B) the allele for blue hydrangea being com
b
A woman and her spouse both show the normal phenotype for pigmentation, but both had one parent who was an
albino. Albinism is an autosomal recessive trait.
What is the probability that their first child will be an albino?
A) 0
B) 1/4
C) 1/2
D) 3/4
E) 1
b
A woman and her spouse both show the normal phenotype for pigmentation, but both had one parent who was an albino. Albinism is an autosomal recessive trait.
If their first two children have normal pigmentation, what is the probability that their third chi
c
Huntington's disease is caused by a dominant allele. If one of your parents has the disease, what is the
probability that you, too, will have the disease?
A) 1
B) 3/4
C) 1/2
D) 1/4
E) 0
c
59) A woman has six sons. The chance that her next child will be a daughter is
A) 1.
B) 0.
C) 1/2.
D) 1/6.
E) 5/6.
e
People with sickle-cell trait
A) are heterozygous for the sickle-cell allele.
B) are usually healthy.
C) have increased resistance to malaria.
D) produce normal and abnormal hemoglobin.
E) all of the above
a
When a disease is said to have a multifactorial basis, it means that
A) many factors, both genetic and environmental, contribute to the disease.
B) it is caused by a gene with a large number of alleles.
C) it affects a large number of people.
D) it has ma
e
Which of the following terms is least related to the others?
A) pedigree
B) karyotype
C) amniocentesis
D) chorionic villus sampling
E) epistasis
sickle cell
Substitution of the "wrong" amino acid in the hemoglobin protein results in this disorder.
tay-sachs disease
Individuals with this disorder are unable to metabolize certain lipids, affecting proper brain development.
Affected individuals die in early childhood.
huntingtons disease
This is caused by a dominant single gene defect and generally does not appear until the individual is 34-40
phenklyetonuria
Effects of this recessive disorder can be completely overcome by regulating the diet of the affected individual.
cystic fibrosis
This results from a defect in membrane proteins that normally function in chloride ion transport.
d
Which of the following techniques involves the preparation of a karyotype?
A) amniocentesis
B) chorionic villus sampling
C) fetoscopy
D) A and B only
E) A, B, and C
d
All the offspring of a cross between a black-eyed MendAlien and an orange-eyed MendAlien have black eyes.
This means that the allele for black eyes is ________ the allele for orange eyes.
A) codominant to
B) recessive to
C) more aggressive than
D) dominan
b
What is the expected phenotypic ratio of a cross between two orange-eyed MendAliens?
A) 3 black-eyed:1 orange-eyed
B) 0 black-eyed:1 orange-eyed
C) 1 black-eyed:3 orange-eyed
D) 1 black-eyed:0 orange-eyed
E) 1 black-eyed:1 orange-eyed
a
Andalusian chickens with the genotype CBCB are black, those with the genotype CBCW are gray. What is the
relationship between the CB and the CW alleles?
A) CB is dominant to CW.
B) CB is recessive to CW.
C) CW is dominant to CB.
D) The relationship is one
a
Black eyes are dominant to orange eyes, and green skin is dominant to white skin. Sam, a MendAlien with
black eyes and green skin, has a parent with orange eyes and white skin. Carole is MendAlien with orange eyes and
white skin. If Sam and Carole were to
d
All the offspring of a cross between a red-flowered plant and a white-flowered plant have pink flowers. This
means that the allele for red flowers is ________ to the allele for white flowers.
A) dominant
B) codominant
C) pleiotropic
D) incompletely domina
1/9
Karen and Steve each have a sibling with sickle-cell disease. Neither Karen nor Steve nor any of their parents
have the disease, and none of them have been tested to reveal sickle-cell trait. Based on this incomplete information,
calculate the probability
chromosome theory of inheritance
a basic principle in biology stating that genes are located on chromosomes and that the behavior of chromosomes during meiosis accounts for inheritance patterns
wild type
an individual with the phenotype most commonly observed in natural populations; also refers to the phenotype itself
sex linked gene
a gene located on the X or Y chromosome, resulting in a distinctive pattern of inheritance
Duchenne muscular dystrophy
a human genetic disease caused by a sex-linked recessive allele and characterized by progressive weakening and a loss of muscle tissue
hemophilia
a human genetic disease caused by a sex-linked recessive allele resulting in the absence of one or more blood-clotting proteins and characterized by excessive bleeding following injury
Barr body
a dense object lying along the inside of the nuclear envelope in cells of female mammals, representing a highly condensed, inactivated X chromosome
linked genes
these are located close enough together on a chromosome that they tend to be inherited together
genetic recombination
general term for the production of offspring with combinations of traits that differ from those found in either parent
parental type
an offspring with a phenotype that matches one of the parental phenotypes; also refers to the phenotype itself
recombinant type
an offspring whose phenotype differs from that of the parents; also refers to the phenotype itself
crossing over
the reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis
genetic map
an ordered list of genetic loci along a chromosome
linkage map
this is based on the frequencies of recombination between markers during crossing over of homologous chromosomes
map unit
a measurement of the distance between two genes, equivalent to a 1% recombination frequency
cytogenetic map
a chart of a chromosome that locates genes with respect to chromosomal features distinguishable in a microscope
nondisjunction
an error in meiosis or mitosis in which members of a pair of homologous chromosomes or a pair of sister chromatids fail to separate properly from each other
aneuploidy
a chromosomal aberration in which one or more chromosomes are present in extra copies or are deficient in number
monosomic
refers to a cell that has only one copy of a particular chromosome instead of the normal two
trisomic
refers to a diploid cell that has three copies of a particular chromosome instead of the normal two
polyploidy
a chromosomal alteration, due to an accident of cell division, in which the organism possesses more than two complete chromosome sets
deletion
a deficiency in a chromosome resulting from the loss of a fragment through breakage
duplication
an aberration in chromosome structure due to fusion with a fragment from a homologous chromosome, such that a portion of a chromosome is repeated
inversion
an aberration in chromosome structure resulting from reattachment of a chromosomal fragment in a reverse orientation to the chromosome from which it originated
translocation
an aberration in chromosome structure resulting from attachment of a chromosomal fragment to a nonhomologous chromosome
Down syndrome
a human genetic disease caused by the presence of an extra chromosome 21 and characterized by mental retardation and heart and respiratory defects
genomic imprinting
a phenomenon in which expression of an allele in offspring depends on whether the allele is inherited from the male or female parent
blending inheritance
hypothesis that traits blended like paint
true-breeding
crossing alleles to produce offspring that produce offspring of the same variety when they self-pollinate; allows for predictability
P generation
parental generation
F1 generation
first filial generation
F2 generation
second filial generation; produced by F1 offspring
law of unit factors
states that there are two factors controlling every trait in an individual
allele
a version of a gene
dominant
an allele that is expressed whenever present
recessive
an allele that is expressed only in the absence of a dominant allele
homozygous
an organism that has a pair of identical alleles for a gene
heterozygous
an organism that has two different alleles for a gene
genotype
the genetic makeup of an organism
phenotype
an organism's appearance or observable traits
Punnett squares
predict the allele composition of offspring from a cross between individuals of known genetic makeup
law of segregation
two alleles for a heritable trait separate during gamete formation and end up in different gametes
testcross
determines if an organism is homozygous or heterozygous
backcross
used when an individual is traced back to find parents
in-breeding
occurs when closely-related individuals mate
incomplete dominance
seen in flowers that have different colored petals; the two alleles are both dominant, meaning they are expressed together in the phenotype when present
codominance
both alleles are still dominant, but they are expressed separately in the phenotype
complete dominance
when a homozygous dominant and heterozygous genotype produce the same phenotype
multiple alleles
when some genes require more than three alleles in order to be expressed
dihybrid cross
a cross that focuses on two traits
law of independent assortment
the inheritance of one gene has no effect on the inheritance of another gene
rule of multiplication
used to determine the probability of two or more independent events occurring together in some specific combination; overall probability is determined by multiplying the individual probabilities of each indepdent event
rule of addition
the probability that an event can occur in two or more different ways is the sum of the separate probabilities of those ways
lymphocytes
cells of the immune system
B cells
cells of the immune system that mature in the bone marrow; make antibodies
T cells
cells of the immune system that mature in the thymus gland
killer T cells
T cells that kill abnormal cells that are infected by a virus to kill the virus;
O
universal blood donor
AB
universal blood recipient
carrier
someone who appears phenotypically normal with regards to a disorder, but has heterozygous alleles and may therefore transmit the recessive allele to offspring
cystic fibrosis
a recessively inherited disease that results in poor absorption of nutrients from intestines, chronic bronchitis, and recurrent bacterial infections
sickle cell disease
recessively inherited disease that causes cells to become misshapen due to altered hemoglobin; most common among people of African descent
achondroplasia
a dominantly inherited disease that causes a form of dwarfism; caused by mutation in gametes
Huntington's disease
a degenerative disease of the nervous system that is caused by a lethal dominant allele that has no phenotypic effect until ages 35-45
Tay Sachs disease
an inherited disorder in which brain cells cannot metabolize certain lipids because of a dysfunctional enzyme;
Tay Sachs disease
recessive on organismal level, incompletely dominant on biochemical level, and codominant on molecular level
amniocentesis
a technique used beginning at the 14th-16th week of pregnancy that can determine whether a developing fetus has a genetic disease; needle inserted into uterus to extract amniotic fluid, and then cells in fluid are cultured and tested
chorionic villus sampling
technique in which a physician inserts a narrow tube through the cervix into the uterus and suctions out a sample of tissue from the placenta; can be karyotyped immediately
antibodies
molecules that bond specifically to other molecules called antigens
antigens
a toxic or other foreign substance that induces an immune response in the body, especially in the production of antibodies
macrophages
cells in the body that engulf antibodies and foreign invaders simply by association to antibodies
agglutination
when antibodies of one blood type clump around antibodies of another blood type because they are foreign to each other; can lead to a stroke
Rh factor
a component of blood that distinguishes positive from negative; named after rhesus monkeys
pleiotropy
when a single allele has an effect on multiple traits
polygenic inheritance
when multiple genes contribute to a single trait; examples are height and skin color
epistasis
when one gene can alter the expression of another gene
cystic fibrosis
a genetic disorder that is found only in Caucasians; chloride channels are flawed, therefore cell secretions are of incorrect fluidity
heterozygous advantage
when hybrid individuals survive with reproductive success because of an advantage to being a hybrid individual
polydactyly
a genetic disorder that is caused by a dominant allele and results in more than five fingers
chromosomal theory of inheritance
a theory that says that Mendel's factors applied to chromosomes as well
wild type
a trait that is normal or most common
mutant phenotype
an abnormal trait
sex-linked trait
any gene on a sex chromosome
sry gene
a gene on the Y-chromosome that results in a flood of testosteron that activates all genes for male settings, then it shuts off and testosterone is not abundantly produced until puberty
hemizygous
what males are said to be because they only have one X-chromosome
X-inactivation
when females randomly shut down one of their X-chromosomes during embryological development; done by turning that chromosome into heterochromatin form, making it super-coiled
Barr body
the super-coiled version of the randomly inactivated X-chromosome in females
nondisjunction
failure of the chromosomes to separate properly during meiosis; usually occurs in only one tetrad
aneuploidy
cells that exhibit this have an abnormal amount of chromosomes
trisomy-21
another name for down syndrome; what occurs when there is an extra chromosome
Klinefelter syndrome
represented by XXY (male); the individual is taller than normal, has degrees of mental retardation, the testes are small and sterile, a small chest develops
Turner's syndrome
X0 (female--0 means just having one X); individual is shorter than normal, sterile, does not go through puberty, and has no secondary sex characteristics
XXX
a female that is phenotypically normal but is most likely sterile
XYY
a male that could possibly be more aggressive because they have an extra Y-chromosome
chromosomal deletion
chromosomal mutation in which a piece of a chromosome that breaks off and is lost; cell is haploid for a portion of the chromosome
duplication
chromosomal mutation in which a piece of a chromosome breaks off, but it attaches to the homologue so that some genes are found twice on the same chromosome; cell can be phenotypically normal or harmful; gametes are flawed though
inversion
chromosomal mutation in which a piece of the chromosome breaks off, reattaches, but in the wrong direction
translocation
a chromosomal mutation in which a piece breaks off and attaches to a chromosome in a non-homologous pair
reciprocal translocation
a chromosomal mutation in which two pieces on non-homologous pairs break off and switch spots
nonreciprocal crossing over
chromosomal mutation that occurs when, during crossing over, non-equal amounts of DNA get switched
cri du chat
a chromosomal deletion in chromosome 5 that results in children who are mentally retarded, have small heads, and have a cry that sounds like a loud cat; they die at a young age
chronic myeloquous leukemia
when chromosomes 9 and 22 switch; this could be a predisposing factor or cause of this type of cancer
Prader-Willi
a disease caused by a chromosomal deletion in the sperm; same effects as Angelman
Angelman
a disease caused by a chromosomal deletion in the egg; same effects as Prader-Willi
genomic imprinting
how we mark our own DNA to identify which DNA is ours; marked by molecules
Fragile X syndrome
the number one cause of mental retardation; the X chromosome has a piece that is either missing or is weak; caused by a triple repeat, which is a repeat of three nucleotides in a row that is copied thousands of times instead of a few dozen; caused by the
linked genes
genes that are on the same chromosome and therefore affect one another; defies Mendel's law of independent assortment