Week 10 Flashcards
The law of independent assortment __________.
a) can account for a 9:3:3:1 ratio seen in the F2 generation
b) states that the alleles at different loci segregate independently from one another during a dihybrid cross
c) applies only to genes that are present on different chromosomes (or behave as if they were)
d) The first and second choices are correct.
e) The first, second, and third choices are correct.
e) The first, second, and third choices are correct.
Homologous pairs of chromosomes often __________.
a) contain different alleles
b) differ in length
c) carry different genes for different traits
e) are not both present in diploid somatic cells
a) contain different alleles
Pea flowers may be purple (P) or white (p). Pea seeds may be round (R) or wrinkled (r). What proportion of the offspring from the cross PpRr x PpRr will have white flowers and wrinkled seeds?
a) 0
b) 1/16
c) 1/4
d) 1/2
b) 1/16
If a heterozygous plant is allowed to self-pollinate, what proportion of the offspring will also be heterozygous?
a) 1/4
b) 1/3
c) 1/2
d) 2/3
e) all of them
c) 1/2
Flower color in snapdragons is an example of incomplete dominance. When a red-flowered plant is crossed with a white-flowered plant, the F1 generation has pink flowers. If a pink-flowered plant is crossed with another pink-flowered plant, the progeny plants will be __________.
a) 100% red
b) 25% red, 50% pink, and 25% white
c) 50% pink and 50% red
d) 100% pink
e) 25% white and 75% red
b) 25% red, 50% pink, and 25% white
A single genetic locus that controls more than one trait is said to be __________.
a) a quantitative character
b) polygenic
c) pleiotropic
d) epistatic
e) somatic
c) pleiotropic
If a plant variety is true-breeding for a dominant trait, then __________.
a) if the plant were allowed to self-pollinate, the dominant and recessive traits would consistently appear in a 3:1 ratio among the progeny
b) the plant is heterozygous for the trait
c) if the plant were crossed with a heterozygote, one-half of the progeny would show the dominant trait, and one-half would show the recessive trait
d) if the plant were allowed to self-pollinate over many generations, all of the progeny would have the dominant trait
e) the variety is unable to mutate
d) if the plant were allowed to self-pollinate over many generations, all of the progeny would have the dominant trait
- Michelle and Keith are apparently normal, but their daughter was born with alkaptonuria, an inherited metabolic disorder. If alkaptonuria is like most other human hereditary disorders, the probability of their next child being born with alkaptonuria is __________.
a) 0
b) 1/4
c) 1/2
d) 2/3
e) 3/4
b) 1/4
- Tom’s brother suffers from phenylketonuria (PKU), a recessive disorder. The brothers’ parents do not have PKU. What are the chances that Tom, who is normal for this trait, is a carrier of PKU?
1/4
1/3
1/2
2/3
4/3
2/3
A couple, both descended from eastern European (Ashkenazic) Jews, visit a genetic counselor before trying to have children. In view of their ethnic background, the counselor recommends that they be tested to see if they are carriers for __________.
a) cystic fibrosis
b) hemophilia
c) hemochromatosis
d) sickle-cell disease
e) Tay-Sachs disease
e) Tay-Sachs disease
The genetic disease cystic fibrosis is caused by a defective allele that __________.
a) encodes a defective chloride-channel membrane transport protein
b) encodes an enzyme that breaks down muscle fibers
c) encodes a neurotoxin
d) causes hemoglobin molecules to malfunction
e) encodes a dysfunctional enzyme that fails to break down brain lipids
a) encodes a defective chloride-channel membrane transport protein
In people with sickle-cell disease, red blood cells break down, clump, and clog the blood vessels. The blood vessels and the broken cells accumulate in the spleen. Among other things this leads to physical weakness, heart failure, joint pain, and brain damage. Such a suite of symptoms can be explained by __________.
a) side effects of the drugs used to cure sickle-cell disease
the polygenic nature of sickle-cell disease
b) a bacterial infection interacting with the sickle-cell allele
c) the pleiotropic effects of the sickle-cell allele
d) an epistatic interaction between the sickle-cell allele and a proteolytic enzyme gene
c) the pleiotropic effects of the sickle-cell allele
- Heart disease, diabetes, cancer, alcoholism, and many mental illnesses can best be described as __________.
a) the symptoms of Huntington’s disease
b) simple Mendelian disorders
c) the results of an unhealthy lifestyle
d) infectious diseases caused by microorganisms
e) multifactorial disorders with a possible polygenic component
e) multifactorial disorders with a possible polygenic component
How does codominance at the molecular level help to explain why evolutionary processes haven’t resulted in the elimination of the sickle-cell allele among people of African descent?
a) Individuals only need one normal allele to have completely normal hemoglobin and reduced densities of malaria parasites in their red blood cells.
b) Individuals with normal and sickle-cell hemoglobin in their red blood cells are usually healthy and, when infected by the malaria parasite, have lower parasite densities and, thus, reduced malaria symptoms.
c) The presence of both normal and sickle-shaped hemoglobin in the red blood cells of heterozygous individuals provides immunity to infection by the malaria parasite.
d) Individuals with two sickle-cell alleles are immune to infection by the malaria parasite.
e) None of the listed choices are correct.
b) Individuals with normal and sickle-cell hemoglobin in their red blood cells are usually healthy and, when infected by the malaria parasite, have lower parasite densities and, thus, reduced malaria symptoms.
How many genes are present in the human genome?
a) 23
b) 46
c) hundreds
d) tens of thousands
e) a virtually infinite number
d) tens of thousands
What is a locus?
a) a structure that appears during prophase I and consists of two paired genes
b) the precise DNA sequence of a gene
c) a type of spore made only by fungi
d) the specific location of a gene along the length of a chromosome
e) a cell with two chromosome sets
d) the specific location of a gene along the length of a chromosome
A = big apples; R = red apples; a = small apples; r = yellow apples.
You have one tree that produces big yellow apples and another tree that produces small red apples. When the two are crossed, you find that half of the new trees produce big red apples and half produce big yellow apples. What are the genotypes of the parents?
a) AaRr and AaRr
b) AaRr and aarr
c) AARr and Aarr
d) AArr and aaRr
e) Aarr and aaRr
d) AArr and aaRr
A clone is the product of __________.
a) asexual reproduction
b) sexual reproduction
c) mitosis
d) The first and third listed responses are correct.
e) The second and fourth listed responses are correct.
d) The first and third listed responses are correct.
A karyotype is __________.
a) a method of identifying crossover events
b) all the possible gametes a person could produce
c) a list of all the genes a person carries
d) a display of all of an individual’s chromosomes arranged in pairs
d) a display of all of an individual’s chromosomes arranged in pairs
How many pairs of autosomes do humans have?
23
22
2
12
It depends on the sex of the individual.
22
Assume tall (T) is completely dominant to dwarf (t) in a certain species of plant. If a homozygous dominant individual is crossed with a homozygous dwarf, the offspring will __________.
a) all be tall with a genotypes of Tt
b) all be intermediate in height with a genotypes of Tt
c) be 1/2 tall and 1/2 dwarf because the genotype is Tt and tt
d) all will be short
e) be 3/4 tall and 1/4 dwarf because of genotypes Tt and tt
a) all be tall with a genotypes of Tt
Somatic cells in humans contain __________ set(s) of chromosomes and are therefore termed __________.
one … haploid
two … diploid
three … triploid
two … haploid
one … diploid
two … diploid
Crossing over occurs during __________.
a) prophase II
b) metaphase II
c) metaphase I
d) cytokinesis
e) prophase I
e) prophase I
The F1 generation differed from the F2 in Mendel’s experiments in that __________.
a) all of the F1 showed the dominant phenotype, and all of the F2 showed the recessive phenotype
b) all of the F1 showed the dominant phenotype, whereas only half of the F2 did
c) all of the F1 showed the dominant phenotype, but only three-fourths of the F2 did
d) none of the F1 showed the dominant phenotype, but one-half of the F2 did
e) one-half of the F1 showed the dominant phenotype, and three-fourths of the F2 did
c) all of the F1 showed the dominant phenotype, but only three-fourths of the F2 did
Physically, what are different alleles?
a) Different alleles are different particles found in gametes.
b) Different alleles are different DNA sequences found at the same locus on homologous chromosomes.
c) Different alleles are different DNA sequences found at the same locus on sister chromatids.
d) Different alleles are different phenotypes for a particular character.
e) None of the listed choices are correct.
b) Different alleles are different DNA sequences found at the same locus on homologous chromosomes.
Through independent assortment alone, humans (2n = 46) can create 8,388,608 combinations of chromosomes. How many chromosomal combinations can a fruit fly (2n = 8) make through independent assortment alone?
a) 8
b) 16
c) 1,458,888
d) 8,388,608
e) 24
b) 16
In Mendel’s monohybrid cross of purple-flowered and white-flowered peas, all members of the F1 generation had the __________ phenotype because their genotype was __________ at the flower-color locus.
a) white-flowered … heterozygous
b) purple-flowered … homozygous recessive
c) white-flowered … homozygous recessive
d) purple-flowered … homozygous dominant
e) purple-flowered … heterozygous
e) purple-flowered … heterozygous
If the two traits that Mendel looked at in his dihybrid cross of smooth yellow peas with wrinkled green peas had been controlled by genes that were located near each other on the same chromosome, then the F2 generation __________.
a) would have contained only individuals that were heterozygous at both loci
b) would have deviated from the 9:3:3:1 phenotypic ratio that is predicted by the law of independent assortment
c) would have contained no individuals that were heterozygous at both loci
d) would have contained four phenotypes in a 9:3:3:1 ratio
b) would have deviated from the 9:3:3:1 phenotypic ratio that is predicted by the law of independent assortment
Albinism in humans occurs when both alleles at a locus produce defective enzymes in the biochemical pathway leading to the pigment melanin. Given that heterozygotes are normally pigmented, which of the following statements is correct?
a) One normal allele produces sufficient melanin as compared to two normal alleles.
b) Each defective allele produces a little bit of melanin.
c) Two normal alleles are needed for normal melanin production.
d) The two alleles are codominant.
a) One normal allele produces sufficient melanin as compared to two normal alleles.
