Chapter 14

25 July 2022
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The effect of the environment on a phenotype is referred to as __________.
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multifactorial
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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 __________.
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would have deviated from the 9:3:3:1 phenotypic ratio that is predicted by the law of independent assortment
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Achondroplasia, a type of dwarfism, and Huntington's disease are examples of __________, with the exception that the Huntington's allele is __________.
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dominant inherited disorders; lethal
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Which choice below is a basic difference between Mendel's particulate hypothesis and the hypothesis of blending inheritance? The blending inheritance hypothesis, but not the particulate hypothesis, maintained that mutation is the major source of new gene combinations. The blending inheritance hypothesis, but not the particulate hypothesis, maintained that the traits governed by genes in the egg are different from the traits governed by genes in the sperm. The blending inheritance hypothesis, but not the particulate hypothesis, maintained that the two alleles at any given locus are always different. The blending inheritance hypothesis, but not the particulate hypothesis, maintained that after a mating, the genetic material provided by each of the two parents is mixed in the offspring, losing its individual identity.
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The blending inheritance hypothesis, but not the particulate hypothesis, maintained that after a mating, the genetic material provided by each of the two parents is mixed in the offspring, losing its individual identity.
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In incomplete dominance, the offspring __________.
In incomplete dominance, the offspring __________.
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will have an appearance that's intermediate between those of the two parental types For some genes, neither allele is completely dominant, and the F1 hybrids have a phenotype somewhere between those of the two parental varieties. This phenomenon, called incomplete dominance, is seen when red snapdragons are crossed with white snapdragons: All the F1 hybrids have pink flowers. This third, intermediate phenotype results from flowers of the heterozygotes having less red pigment than the red homozygotes.
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Human ABO groups are best described as an example of __________.
Human ABO groups are best described as an example of __________.
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multiple alleles Only two alleles exist for the pea characters that Mendel studied, but most genes exist in more than two allelic forms. The ABO blood groups in humans, for instance, are determined by three alleles of a single gene: IA, IB, and i. A person's blood group may be one of four types: A, B, AB, or O. These letters refer to two carbohydrates—A and B—that may be found on the surface of red blood cells. A person's blood cells may have carbohydrate A (type A blood), carbohydrate B (type B), both (type AB), or neither (type O). Matching compatible blood groups is critical for safe blood transfusions.
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The term "true-breeding plants" means __________.
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that self-pollinating plants will always produce the same trait of a particular character
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If a plant variety is true-breeding for a dominant trait, then __________.
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if the plant were allowed to self-pollinate, all of the progeny would have the dominant trait For example, a plant with purple flowers is true-breeding if the seeds produced by self-pollination in successive generations all give rise to plants that also have purple flowers. In this case, the parent shows the dominant trait, so the progeny would as well. All the progeny would show the same phenotype, so a 3:1 phenotype ratio would not be observed among the progeny. A true breeding can also be described as homozygous, but not heterozygous. Even the genes of true-breeding varieties can mutate. previous
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A family tree that describes traits in families is called a __________.
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pedigree analysis
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What kind of protection does the Genetic Information Nondiscrimination Act of 2008 provide the public with regard to the use of genetic information?
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The law prohibits the use of genetic test information to deny insurance coverage or employment to individuals.
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Huntington's disease is an example of a genetic disorder caused by __________.
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a lethal dominant allele that afflicts an individual later in life
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Mendel studied __________, heritable features that vary among individuals; each variant is called a __________.
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characters; trait
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In humans, height and skin color have continuous variation in the population because of __________.
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polygenic inheritance
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The F1 generation differed from the F2 in Mendel's experiments in that __________.
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all of the F1 showed the dominant phenotype, but only three-fourths of the F2 did
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Mendel's law of segregation states that __________.
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the two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes In terms of chromosomes, this segregation corresponds to the distribution of the two members of a pair of homologous chromosomes to different gametes in meiosis. Note that if an organism has identical alleles for a particular character—that is, the organism is true-breeding for that character—then that allele is present in all gametes. But if different alleles are present, as in the F1 hybrids, then 50% of the gametes receive the dominant allele and 50% receive the recessive allele.
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If a heterozygous plant is allowed to self-pollinate, what proportion of the offspring will also be heterozygous?
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1/2
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Fetal cells may be removed along with fluid from the womb by a process known as __________.
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amniocentesis
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An alternative version of a gene is called a(n) __________.
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allele
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In Labrador retrievers, a dog that has the genotype BBee, where BB produces black-pigmented fur and ee produces yellow-pigmented fur, would have __________ fur and would exhibit __________.
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yellow; epistasis
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A red bull is crossed with a white cow and all of the offspring are roan, an intermediate color that is caused by the presence of both red and white hairs. This is an example of genes that are __________.
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codominant
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In a typical pea experiment, two true-breeding plants with distinct traits of a single character are called the __________, and the offspring are called the __________, which will always be __________.
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P (or parental) generation; F1 (or first filial) generation; hybrid
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Color in squash is controlled by epistatic interactions in which color is recessive to no color. At the first locus white squash (W) is dominant to colored squash (w). At the second locus yellow (Y) is dominant to green (y). What is the phenotype of a squash with the genotype wwYy?
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yellow
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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 __________.
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the pleiotropic effects of the sickle-cell allele
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If an organism that is homozygous dominant is crossed with a heterozygote for that trait, the offspring will be __________.
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all of the dominant phenotype
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Besides the fact that pea plants have a short generation time, the key to Mendel's successful plant-breeding experiments was that pea plants usually __________.
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self-pollinate
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Human blood groups are governed by three alleles, A, B, and O. A and B are codominant and O is recessive to both. A man who has type B blood and a woman who has type A blood could have children of which of the following phenotypes?
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A, B, AB, or O
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Pea plants are tall if they have the genotype TT or Tt, and they are short if they have genotype tt. A tall plant is mated with a short plant. Which outcome below would indicate that the tall parent plant was heterozygous?
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The ratio of tall offspring to short offspring is 1:1.
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__________ occurs when a single gene affects the phenotype of many characters in an individual.
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A pleiotropic effect
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In incomplete dominance, the offspring __________.
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will have an appearance that's intermediate between those of the two parental types
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In addition to the ABO system, humans have other blood groups, including the MN system. Individuals who have alleles for both M and N show __________ for the M and N red blood cell surface antigens.
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codominance
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A man who can roll his tongue and a woman who cannot roll her tongue have a son who can roll his tongue (R = can roll tongue; r = can't roll tongue). The son is curious about whether his father is homozygous or heterozygous for the tongue-rolling trait. Which of the following facts would allow him to know?
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His father's mother cannot roll her tongue.