The dominant trait, Huntington disease causes severe neural/brain damage at approximately age 40. A female whose mother has Huntington disease marries a male whose parents are normal. It is not known if the female has the disease. What is the probability
25%
The following symbols ~ = � indicate a consanguineous mating. True or False
True
A rare recessive trait in a pedigree is indicated by which pattern of inheritance?
1)vertical
2)horizontal
3)diagonal
4)both vertical and horizontal
5)None of these is correct.
horizontal
An alternative form of a single gene is known as
1)parental.
2)dihybrid.
3)reciprocal.
4)allele.
5)recessive.
allele
Suppose that in plants, smooth seeds (S) are dominant to wrinkled seeds (s) and tall plants (T) are dominant to short plants (t). A tall plant with smooth seeds was backcrossed to a parent that was short and wrinkled. What proportion of the progeny is exp
1/4
In a monohybrid cross AA � aa, what proportion of heterozygotes is expected among the F2 offspring?
1) 1/4
2) 1/2
3) 3/4
4) All are heterozygotes.
5) None are heterozygotes.
1/2
Using the product rule, one would calculate the probability of parents having six children who are all boys as (�)6.
1) True
2) False
true
In a dihybrid cross AAbb � aaBB, what proportion of the F2 offspring is expected to be homozygotic for at least one gene?
1) 1/4
2) 1/2
3) 3/4
4) All are homozygotes.
5) None are homozygotes.
3/4
An allele that expresses its phenotype even when heterozygous with a recessive allele is termed
1) recessive.
2) recombinant.
3) dominant.
4) parental.
5) independent.
dominant
In some genetically engineered corn plants the dominant gene (BT) produces a protein that is lethal to certain flying insect pests that eat the corn plants. It was also found that the pollen could cause death in some flying insects. If the corn plant is h
1/2
Suppose that in plants, smooth seeds (S) are dominant to wrinkled seeds (s) and tall plants (T) are dominant to short plants (t). A tall plant with smooth seeds was backcrossed to a parent that was short and wrinkled. What proportion of the progeny is exp
1/4
The first offspring from the parents are called
1) P.
2) F1.
3) F2.
4) testcross.
5) backcross
F1
The diploid cell formed by the fertilization of the egg by the sperm during sexual reproduction is a
1) reciprocal.
2) zygote.
3) dihybrid.
4) gamete.
5) monohybrid
zygote
When Mendel repeated his pea experiments in beans, he found flowers that ranged from white to pale violet to purple. This is due to bean flower color being determined by more than one gene.
1) True
2) False
true
In the dihybrid cross AaBb � aabb, what proportion of heterozygotes for both gene pairs is expected among the F1 offspring?
1) 1/4
2) 1/2
3) 3/4
4) All are heterozygotes.
5) None are heterozygotes.
1/4
The phenotypic ratio 9:3:4 may indicate
1) complete dominance.
2) codominance.
3) epistasis.
4) recessive lethal.
5) codominance and epistasis only.
epistasis
The phenotypic ratio 2:1 may indicate
1) complete dominance.
2) codominance.
3) epistasis.
4) recessive lethal.
5) codominance and epistasis only.
recessive lethal
The phenomenon of a single gene determining a number of distinct and seemingly unrelated characteristics is known as pleiotropy.
1) True
2) False
True
Which of the following is not a phenotypic description of allele interactions affecting the expression of traits?
1) incomplete dominance
2) codominance
3) polymorphic
4) multifactorial
5) pleiotrophic
multifactorial
In epistasis, one gene's alleles mask the effects of another gene's alleles.
1) True
2) False
True
Which of the following phenotypic ratios show incomplete dominance?
1) 2:1
2) 3:1
3) 1:2:1
4) 1:1
5) 4:1
1:2:1
A _____________ results whenever the nucleotide sequence is changed.
1) phenotype
2) genotype
3) mutation
4) trait
5) character
mutation
Different alleles indicate unique genes.
1) True
2) False
False
Mutations are the source of new alleles.
1) True
2) False
True
A mutant allele has a rare occurrence in a population.
1) True
2) False
True
An interaction between non-allelic genes that results in the masking of expression of a phenotype is
1) epistasis.
2) epigenetics.
3) dominance.
4) codominance.
5) incomplete dominance.
epistasis
The phenotypic ratio 9:7 may indicate
1) complete dominance.
2) codominance.
3) epistasis.
4) recessive lethal.
5) complementary gene action.
complementary gene action
Which of the following ratios demonstrate gene interaction?
1) 2:1
2) 3:1
3) 1:2:1
4) 9:3:4
5) 1:3
9:3:4
The phenotypic ratio 1:2:1 may indicate
1) complete dominance.
2) codominance.
3) epistasis.
4) recessive lethal.
5) codominance and epistasis only.
codominance
When a late blooming pea and an early blooming pea are crossed and an intermediate phenotype occurs, this result would suggest incomplete dominant inheritance.
1) True
2) False
True
A female fruit fly with singed bristles was mated with a male from a true-breeding wild-type stock with long bristles. All of the F1 females had wild-type bristles and all of the F1 males had singed bristles. If the F1 flies are intercrossed, the expected
1:1 in both sexes
Mitosis results in _______ chromosome number, whereas meiosis results in _______ chromosome number.
1) a doubling of, no change in
2) no change in, no change in
3) a reduction by half in, no change in
4) no change in, a doubling of
5) no change in, a redu
no change in, a reduction by half in
Which of the following statements applies to homologous chromatids?
1) They are attached to the same centromere.
2) They are genetically identical.
3) They segregate from each other at anaphase of mitosis.
4) They contain the same genes in the same order
They contain the same genes in the same order but may have different alleles of some genes.
In fruit flies, brown eyes can be caused by the recessive mutations pn (prune), bw (brown) or ry (rosy), which are on the X chromosome, second chromosome, and third chromosome, respectively. Wild-type alleles for all three genes must be present for eyes t
pn
Which of the following events occurs during mitosis but not during meiosis?
1) segregation of sister chromatids
2) pairing of homologous chromosomes
3) crossing-over between homologous chromosomes
4) alignment of chromosomes on the metaphase plate
5) None
None of the choices is correct
Nondisjunction can occur at either the first or second division of meiosis. XXY individuals could arise from nondisjunction at the ______ meiotic division in the ______.
1) first, mother
2) second, mother
3) first, father
4) second, father
5) More than on
More than one of the choices could give rise to XXY individuals
The stage of mitosis when sister chromatids separate from each other and migrate to opposite poles of a cell is called
1) interphase.
2) prophase.
3) metaphase.
4) anaphase.
5) telophase.
anaphase
A cross between a white-eyed female fruit fly and a red-eyed male would generate which of the following types of progeny?
1) red-eyed females and white-eyed males
2) white-eyed females and red-eyed males
3) all red-eyed females and a 50:50 mixture of whit
red-eyed females and white-eyed males
A chromatin-laden nucleus is quiescent.
1) True
2) False
False
A white-eyed female fruit fly is mated to a red-eyed male. One of their progeny is a white-eyed female. This white-eyed daughter likely arose from nondisjunction of the sex chromosomes during _________ in the __________.
1) meiosis I, mother
2) meiosis II
meiosis I or II, mother
In chickens, it is the females that have two different sex chromosomes (Z and W) while the males have two Z chromosomes. A Z-linked gene controls the pattern of the feathers, with the dominant B allele causing the barred pattern and the b allele causing n
barred females � non-barred males
Humans have 22 pairs of autosomes plus one sex chromosome pair. How many autosomes are present in a normal human primary spermatocyte?
1) 22
2) 23
3) 44
4) 45
5) 46
44
What aspect of chromosome behavior most clearly accounts for Mendel's law of independent assortment?
1) Movement of sister chromatids to opposite poles at anaphase II of meiosis
2) Movement of homologous chromosomes to opposite poles at anaphase I of meio
Independent alignment of different homologous pairs on the metaphase I spindle
Ascospores are haploid cells that can germinate, replicate by mitosis, and survive as haploid individuals.
1) True
2) False
true
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?
1) Chiasmata are randomly distributed along chromosomes.
2) All chr
Chiasmata are spaced along a chromosome arm more regularly than would be expected by chance.
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?
1) D and E are on different pairs of chromosomes.
2) D and E are linked and exactly 50 map units apart.
3) D and E are linked and
either D and E are on different pairs of chromosomes or D and E are linked and at least 50 map units apart
Chiasmata are structures of cross over between sister chromatids of homologous chromosomes.
1) True
2) False
False
Which of the following processes can generate recombinant gametes?
1) Segregation of alleles in a heterozygote.
2) Crossing over between two linked heterozygous loci.
3) Independent assortment of two unlinked heterozygous loci.
4) Crossing over between tw
Crossing over between two linked heterozygous loci and independent assortment of two unlinked heterozygous loci
Genes chained together by linkage relationships are known collectively as a linkage group.
1) True
2) False
True
What happens physically during the process of crossing over?
1) Two homologous chromatids break and rejoin at random sites along the chromosome.
2) The genetic information on one chromatid is replaced by copying genetic information from a homologous chrom
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.
Sturtevant's detailed mapping studies of the X chromosome of Drosophila established what genetic principle?
1) That genes are arranged in a linear order on the chromosomes.
2) That genes are carried on chromosomes.
3) That sex determination is controlled
That genes are arranged in a linear order on the chromosomes.
When considering the chi-square test, a p value of 0.05 is often considered significant but it is actually an arbitrary assignment of significance.
1) True
2) False
True
What is the value of X2 for a test of the hypothesis that the sn and car genes are unlinked?
1) 0.5
2) 1.0
3) 2.0
4) 0.4
5) 20
2.0
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?
1) 15 map units
2) 35 map units
3) either 15 map units or 35 map units, depending on the
either 15 map units or 35 map units, depending on the order of the genes