Chapter 9
Justin has type A blood and his wife Brittany has type B blood. Justin's parents both have type AB blood, and Brittany's parents also both have type AB blood. What are the chances that Justin and Brittany's son Theodore has type A blood?
0%
According to scientists, about what percentage of men currently living in Central Asia may be descended from the Mongolian ruler Genghis Khan?
8%
If A is dominant to a and B is dominant to b, what is the expected phenotypic ratio of the cross AaBb × AaBb?
9:3:3:1
The phenotypic ratio resulting from a dihybrid cross of two heterozygote individuals showing independent assortment is expected to be
9:3:3:1
Which of the following statements regarding genotypes and phenotypes is false? -An organism with two different alleles for a single trait is said to be homozygous for that trait. -The expressed physical traits of an organism are called its phenotype. -The genetic makeup of an organism constitutes its genotype. -Alleles are alternate forms of a gene.
An organism with two different alleles for a single trait is said to be homozygous for that trait.
In some cats, black coat color (B) is dominant over brown (B) and a striped fur pattern (S) is dominant over a marbled fur pattern (s). You rescued a black striped cat from an animal shelter but could not determine its exact genotype. To do so, you mated the cat with a brown marbled cat. The mating produced 3 brown marbled, 2 brown striped, 2 black marbled, and 3 black striped. Immediately, you concluded the genotype of your rescued cat was -BbSS. -BBSS. -BbSs. -BBSs.
BbSs
Dr. Smith's parents have normal hearing. However, Dr. Smith has an inherited form of deafness. Deafness is a recessive trait that is associated with the abnormal allele d. The normal allele at this locus, associated with normal hearing, is D. Dr. Smith's parents could have which of the following genotypes? -Dd and Dd -Dd and DD -dd and dd -DD and dd
Dd and Dd
If independent assortment did not occur, which of the following would be true? -Genes for two different traits would be inherited together as a pair. -A dihybrid cross of heterozygous individuals would yield four different phenotypes. -Meiosis II would not be required to produce gametes, as meiosis I would be sufficient. -Each sperm and egg would carry more than one allele for a specific gene.
Genes for two different traits would be inherited together as a pair.
Which of the following statements is false? -Incomplete dominance supports the blending hypothesis. -ABO blood groups can provide evidence of paternity. -The four blood types result from various combinations of the three different ABO alleles. -The impact of a single gene on more than one character is called pleiotropy.
Incomplete dominance supports the blending hypothesis.
What is meant by the statement that "male bees are fatherless"? -The queen bee's mate dies before the male eggs hatch. -Male bees are produced by budding. -Male bees don't play a role in the rearing of bee young. -Male bees develop from unfertilized eggs
Male bees develop from unfertilized eggs.
Which of the following statements regarding genetic testing is false? -Genetic testing before birth requires the collection of fetal cells. -The screening of newborns can catch inherited disorders right after birth. -Most human genetic diseases are treatable if caught early. -Carrier testing helps determine whether a person carries a potentially harmful disorder.
Most human genetic diseases are treatable if caught early.
Which of the following statements best explains why dominant alleles that cause lethal disorders are less common than recessive alleles that cause lethal disorders? -The presence of a lethal dominant allele causes sterility. -Lethal disorders caused by dominant alleles are usually more severe than lethal disorders caused by recessive alleles. -Unlike lethal disorders caused by recessive alleles, lethal disorders caused by dominant alleles usually cause the death of the embryo. -Most individuals carrying a lethal dominant allele have the disorder and die before they reproduce, whereas individuals carrying a lethal recessive allele are more likely to be healthy and reproduce.
Most individuals carrying a lethal dominant allele have the disorder and die before they reproduce, whereas individuals carrying a lethal recessive allele are more likely to be healthy and reproduce.
Which of the following statements best represents the theory of pangenesis developed by Hippocrates? -Pregnancy is a spontaneous event, and the characteristics of the offspring are determined by the gods. -Offspring inherit the traits of either the mother or the father, but not both. -Heritable traits are influenced by the environment and the behaviors of the parents. -Particles called pangenes, which originate in each part of an organism's body, collect in the sperm or eggs and are passed on to the next generation.
Particles called pangenes, which originate in each part of an organism's body, collect in the sperm or eggs and are passed on to the next generation.
Which of the following statements regarding sickle-cell disease is false? -About one in 10 African Americans is a carrier of sickle-cell disease. -All of the symptoms of sickle-cell disease result from the actions of just one allele. -Sickle-cell disease causes white blood cells to be sickle-shaped. -Persons who are heterozygous for sickle-cell disease are also resistant to malaria.
Sickle-cell disease causes white blood cells to be sickle-shaped.
Which of the following statements regarding hypotheses about inheritance is false? -The blending hypothesis suggests that all of the traits of the offspring come from either the mother or the father. -The theory of pangenesis incorrectly suggests that reproductive cells receive particles from somatic cells. -The blending hypothesis does not explain how traits that disappear in one generation can reappear in later generations. -Contrary to the theory of pangenesis, somatic cells do not influence eggs or sperm.
The blending hypothesis suggests that all of the traits of the offspring come from either the mother or the father.
A colorblind woman marries a man who is not colorblind. All of their sons, but none of their daughters, are colorblind. Which of the following statements correctly explains these results? -The gene for color vision is found on the X chromosome. -The gene for color vision is incompletely dominant to the gene for sex determination. -The gene for color vision is found on the Y chromosome. -The gene for color vision is codominant with the gene for sex determination.
The gene for color vision is found on the X chromosome.
Which of the following statements regarding cross-breeding and hybridization is false? -The parental plants of a cross are the P generation. -The offspring of two different varieties are called hybrids. -The hybrid offspring of a cross are the P1 generation. -The hybrid offspring of an F1 cross are the F2 generation.
The hybrid offspring of a cross are the P1 generation.
You prepare a karyotype from a cell from an unknown organism. Upon analysis, you find 22 pairs of chromosomes that are each of equal length, and also a single pair that has one chromosome longer than the other. What can you conclude from this information? -This cell is likely haploid. -The organism that this cell came from is likely a male. -The organism that this cell came from is likely a female. -The organism that this cell came from has a genetic disease.
The organism that this cell came from is likely a male.
The sex chromosome complement of a normal human female is
XX
A monohybrid cross is -a breeding experiment in which the parental varieties have only one prominent trait. -a breeding experiment in which the parental varieties have only one trait in common. -the second generation of a self-fertilized plant. -a breeding experiment in which the parental varieties differ in only one character.
a breeding experiment in which the parental varieties differ in only one character.
A testcross is -a mating between an individual of unknown genotype and an individual heterozygous for the trait of interest. -a mating between two individuals heterozygous for the trait of interest. -a mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest. -a mating between two individuals of unknown genotype.
a mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest.
Research since Mendel's time has established that the law of segregation of genes during gamete formation -applies to all sexually reproducing organisms. -applies to all forms of life. -is invalid. -applies to all asexually reproducing organisms.
applies to all sexually reproducing organisms.
How is sex determined in most ants and bees? -by the size of the sex chromosome -by the number of chromosomes -by the Z-W system -by the X-Y system
by the number of chromosomes
For most sexually reproducing organisms, Mendel's laws -explain the biological mechanisms behind why certain genes are dominant or recessive. -can predict whether offspring will be male or female with 100% accuracy. -cannot strictly account for the patterns of inheritance of many traits. -help us understand the global geographic patterns of genetic disease.
cannot strictly account for the patterns of inheritance of many traits.
A person with AB blood illustrates the principle of -codominance. -incomplete dominance. -pleiotropy. -polygenic inheritance.
codominance
The expression of both alleles for a trait in a heterozygous individual illustrates -pleiotropy. -incomplete dominance. -polygenic inheritance. -codominance.
codominance
Sickle-cell disease is an example of -multiple alleles, pleiotropy, and blended inheritance. -codominance and multiple alleles. -multiple alleles and pleiotropy. -codominance and pleiotropy.
codominance and pleiotropy.
The mechanism that "breaks" the linkage between linked genes is
crossing over.
Linked genes generally -reflect a pattern of codominance. -show pleiotropy. -show incomplete dominance. -do not follow the laws of independent assortment.
do not follow the laws of independent assortment.
Mendel's law of independent assortment states that -independent sorting of genes produces polyploid plants under some circumstances. -each pair of alleles segregates independently of the other pairs of alleles during gamete formation. -genes are sorted concurrently during gamete formation. -chromosomes sort independently of each other during mitosis and meiosis.
each pair of alleles segregates independently of the other pairs of alleles during gamete formation.
The individual features of all organisms are the result of -genetics. -genetics and the environment. -the environment. -the environment and individual needs.
genetics and the environment.
A carrier of a genetic disorder who does not show symptoms is most likely to be ________ to transmit it to offspring. -heterozygous for the trait and unable -homozygous for the trait and able -heterozygous for the trait and able -homozygous for the trait and unable
heterozygous for the trait and able
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. -incompletely dominant -dominant -recessive -codominant
incompletely dominant
Any gene located on a sex chromosome -will exhibit codominance. -is called a sex-linked gene. -will exhibit pleiotropy. -is called a recessive gene.
is called a sex-linked gene.
Amniocentesis and chorionic villus sampling allow for ________ and ________ of the fetus so that it can be tested for abnormalities. -karyotyping; biochemical testing -sexing; imaging -direct observation; biochemical testing -imaging; karyotyping
karyotyping; biochemical testing
Genes located close together on the same chromosomes are referred to as ________ genes and generally ________. -homologous; are inherited together -linked; sort independently during meiosis -codependent; do not sort independently during meiosis -linked; do not sort independently during meiosis
linked; do not sort independently during meiosis
Sex-linked conditions are more common in men than in women because -the genes associated with the sex-linked conditions are linked to the Y chromosome, which determines maleness. -the sex chromosomes are more active in men than in women. -men acquire two copies of the defective gene during fertilization. -men need to inherit only one copy of the recessive allele for the condition to be fully expressed.
men need to inherit only one copy of the recessive allele for the condition to be fully expressed.
Most people afflicted with recessive disorders are born to parents who were -not affected at all by the disease. -subjected to some environmental toxin that caused the disease in their children. -slightly affected by the disease, showing some but not all of the symptoms. -both affected by the disease.
not affected at all by the disease.
How many sex chromosomes are in a human gamete?
one
What is the normal complement of sex chromosomes in a human male? -one X chromosome and one Y chromosome -two Y chromosomes -one Y chromosome -two X chromosomes and one Y chromosome
one X chromosome and one Y chromosome
Mendel conducted his most memorable experiments on
peas
Which of the following terms refers to a situation where a single phenotypic character is determined by the additive effects of two or more genes? -polygenic inheritance -incomplete dominance -pleiotropy -codominance
polygenic inheritance
Which plants in this figure must all be heterozygous? -purple-flowered plants in the F1 generation -purple-flowered plants in the P generation -white-flowered plants in the P generation -purple-flowered plants in the F2 generation
purple-flowered plants in the F1 generation
Most genetic disorders of humans are caused by -a mutation that occurs in the egg, sperm, or zygote. -dominant alleles. -multiple alleles. -recessive alleles.
recessive alleles.
Female inheritance patterns cannot be analyzed by simply studying the X chromosome because -the X chromosome is too large to analyze effectively. -the X chromosome is obtained from both father and mother. -one X chromosome is deactivated in females. -the X chromosome sometimes exchanges genetic information with the Y chromosome.
the X chromosome is obtained from both father and mother.
Imagine that we mate two black Labrador dogs with normal vision and find that three of the puppies are like the parents, but one puppy is chocolate with normal vision and another is black with PRA (progressive retinal atrophy, a serious disease of vision). We can conclude that -both of the parents are homozygous for both traits. -the alleles for color and vision segregate independently during gamete formation. -the same alleles that control coat color can also cause PRA. -the alleles for color and vision segregate dependently during gamete formation.
the alleles for color and vision segregate independently during gamete formation.
The chromosome theory of inheritance states that -the behavior of chromosomes during meiosis and fertilization accounts for patterns of inheritance. -the behavior of chromosomes during mitosis accounts for inheritance patterns. -chromosomes that exhibit mutations are the source of genetic variation. -humans have 46 chromosomes.
the behavior of chromosomes during meiosis and fertilization accounts for patterns of inheritance.
Recessive X-linked traits are more likely to be expressed in a male fruit fly than a female fruit fly because -the male chromosome is more fragile than the female chromosome. -males are haploid.the male's phenotype results entirely from his single X-linked gene. -the male chromosome is more susceptible to mutations.
the male's phenotype results entirely from his single X-linked gene.
The alleles of a gene are found at ________ chromosomes. -different loci on nonhomologous -the same locus on homologous -different loci on homologous -the same locus on nonhomologous
the same locus on homologous
Varieties of plants in which self-fertilization produces offspring that are identical to the parents are referred to as -the F2 generation. -monohybrid crosses. -true-breeding. -hybrids.
true-breeding.
