Biology notes Ch. 9 FANKS

If independent assortment did not occur, which of the following would be true? A. Genes for two different traits would be inherited together as a pair. B. Each sperm and egg would carry more than one allele for a specific gene. C. A dihybrid cross of heterozygous individuals would yield four different phenotypes. D. Meiosis II would not be required to produce gametes, as meiosis I would be sufficient.

A, Genes for two different traits would be inherited together as a pair.

The chromosome theory of inheritance is based upon which of the following sets of observations? A. Genes segregate; chromosomes come in pairs. B. Genes occur as singular entities; chromosomes come in pairs. C. Genes assort together; chromosomes come in pairs. D. Genes remain associated with one another; so do chromosomes.

A, Genes segregate; chromosomes come in pairs.

Which of the following statements best explains why dominant alleles that cause lethal disorders are less common than recessive alleles that cause lethal disorders? A. 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. B. The presence of a lethal dominant allele causes sterility. C. Lethal disorders caused by dominant alleles are usually more severe than lethal disorders caused by recessive alleles. D. Unlike lethal disorders caused by recessive alleles, lethal disorders caused by dominant alleles usually cause the death of the embryo.

A, 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.

Imagine you're counseling a couple who have undergone carrier screening for Tay-Sachs disease. The man is a carrier, and the woman does not carry the Tay-Sachs allele. How should you advise them? A. They should be informed that if they have a child, the child will not have Tay-Sachs disease but will have a 50% chance of being a carrier of the Tay-Sachs allele. B. They should be informed that if they have a child, there is a 50% chance that the child will have Tay-Sachs disease. C. They should be informed that if they conceive a child, the child will have Tay-Sachs disease. D. They should be informed that if they have a child, there is a 25% chance that the child will have Tay-Sachs disease.

A, They should be informed that if they have a child, the child will not have Tay-Sachs disease but will have a 50% chance of being a carrier of the Tay-Sachs allele.

A person with AB blood illustrates the principle of A. co-dominance. B. incomplete dominance. C. pleiotropy. D. polygenic inheritance.

A, co-dominance

The expression of both alleles for a trait in a heterozygous individual illustrates A. co-dominance. B. polygenic inheritance. C. pleiotropy. D. incomplete domin

A, co-dominance.

The individual features of all organisms are the result of A. genetics and the environment. B. genetics. C. the environment and individual needs. D. the environment.

A, genetics and the environment.

Which of the following is an example of incomplete dominance in humans? A. hypercholesterolemia B. albinism C. ABO blood groups D. skin color

A, hypercholesterolemia

Genes located close together on the same chromosomes are referred to as ________ genes and generally ________. A. linked; do not sort independently during meiosis B. homologous; are inherited together C. linked; sort independently during meiosis D. codependent; do not sort independently during meiosis

A, linked; do not sort independently during meiosis

Most people afflicted with recessive disorders are born to parents who were A. not affected at all by the disease. B. both affected by the disease. C. slightly affected by the disease, showing some but not all of the symptoms. D. subjected to some environmental toxin that caused the disease in their children.

A, not at all affected by the disease

If the two characteristics that Mendel looked at in his dihybrid cross of smooth yellow peas with wrinkled green peas had been controlled by genes that were located close together on the same chromosome, then the F2 generation _____. A. would have deviated from the 9:3:3:1 phenotypic ratio that is predicted by the law of independent assortment B. would have contained no individuals that were heterozygous for both genes C. would have contained only individuals that were heterozygous for both genes D. would have contained four phenotypes in a 9:3:3:1 ratio

A, would have deviated from the 9:3:3:1 phenotypic ratio that is predicted by the law of independent assortment

If one parent is blood type AB and the other is type O, what fraction of their offspring are expected to have blood type A? A. O B. 0.5 C. 0.75 D. 1.0

B, 0.5

You conduct a dihybrid cross. A ________ ratio would make you suspect that the genes are linked. A. 3:1 B. 12:1:1:4 C. 9:3:3:1 D. 1:1:1:1

B, 12:1:1:4

Snapdragons show incomplete dominance in their flowers. A pink snapdragon is crossed with a red snapdragon. What color(s) are the offspring? A. 50% red, 50% white B. 50% red, 50% pink C. 100% red D. 100% pink

B, 50% red, 50% pink

Blood samples are taken from the heel of newborn babies to test for a mutation in the PKU gene, which, if left untreated and in severe cases, can lead to mental retardation, reduced skin pigmentation, and seizures. Which concept is being illustrated by this example? A. polygenic inheritance B. pleiotropy C. incomplete dominance D. co-dominance

B, pleiotropy

Two parents of mixed ethnicity have twins, one of which is born white and one of which is born black. This is because of _____. A. exposure to sunlight B. the polygenic nature of skin color genes C. the pleiotropic effects of skin color genes D. the inheritance of two linked skin color genes

B, the polygenic nature of skin color genes

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? A. 75% B. 25% C. 0% D. 100%

C, 0%

Which of the following statements is false? A. Incomplete dominance supports the blending hypothesis. B. The impact of a single gene on more than one character is called pleiotropy. C. ABO blood groups can provide evidence of paternity. D. The four blood types result from various combinations of the three different ABO alleles.

C, ABO blood groups can provide evidence of paternity.

Two individuals decide to have children. The expected blood group genotypes are 50% of blood type A, and 25% each of blood types AB and B. What genotypes are the parents? A. IA i x ii B. IB i x IA IB C. IA i x IA IB D. IA i x IB i

C, IA i x IA IB

Human genetic disorders _____. A. are most often dominant B. are almost never observed in modern societies C. are most often recessive D. are almost always life-threatening

C, are most often recessive

Linked genes are inherited together. This is because linked genes _____. A. govern traits (such as hair texture and hair color) that are functionally related B. govern traits that have nothing to do with one another C. are on the same chromosome D. have the same alleles residing on them

C, are on the same chromosome

Sickle-cell disease is an example of A. multiple alleles and pleiotropy. B. multiple alleles, pleiotropy, and blended inheritance. C. co-dominance and pleiotropy. D. co-dominance and multiple alleles.

C, co-dominance and pleiotropy.

The mechanism that "breaks" the linkage between linked genes is A. independent assortment. B. pleiotropy. C. crossing over. D. co-dominance.

C, crossing over.

Linked genes generally A. reflect a pattern of codominance. B. show incomplete dominance. C. do not follow the laws of independent assortment. D. show pleiotropy.

C, do not follow the laws of independent assortment.

For most sexually reproducing organisms, Mendel's laws A. explain the biological mechanisms behind why certain genes are dominant or recessive. B. can predict whether offspring will be male or female with 100% accuracy. C. help us understand the global geographic patterns of genetic disease. D. cannot strictly account for the patterns of inheritance of many traits.

C, help us understand the global geographic patterns of genetic disease.

Two identical twins are raised in different environments. They possess _____ genotypes and _____ phenotypes. A. identical ... dissimilar B. contrasting ... identical C. identical ... variable D. identical ... identical

C, identical ... variable

Sturtevant's genetic mapping _____. A. orders genes on a chromosome based on their location with respect to a stained band B. can be constructed only for sex chromosomes C. orders genes on a chromosome based on recombination frequencies D. shows the ordering and exact spacing of genes on a chromosome

C, orders genes on a chromosome based on recombination frequencies

A single allele that controls more than one character is said to be _____. A. autotrophic B. polygenic C. pleiotropic D. linked

C, pleiotropic

The inheritance of height and weight can best be described as __________. A. Mendelian (dominant-recessive) inheritance B. the results of a bad lifestyle C. polygenic and multifactorial D. being caused by microorganisms

C, polygenic and multifactorial

Most genetic disorders of humans are caused by A. a mutation that occurs in the egg, sperm, or zygote. B. dominant alleles. C. recessive alleles. D. multiple alleles.

C, recessive alleles

The chromosome theory of inheritance states that A. chromosomes that exhibit mutations are the source of genetic variation. B. the behavior of chromosomes during mitosis accounts for inheritance patterns. C. the behavior of chromosomes during meiosis and fertilization accounts for patterns of inheritance. D. humans have 46 chromosomes.

C, the behavior of chromosomes during meiosis and fertilization accounts for patterns of inheritance.

n people with sickle-cell disease, red blood cells break down, clump, and clog blood vessels. Blood vessels and broken cells accumulate in the spleen. Among other symptoms, this leads to physical weakness, heart failure, pain, and brain damage. Such a suite of symptoms can be explained by __________. A. 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. side effects of the drugs used to treat sickle-cell disease

C, the pleiotropic effects of the sickle-cell allele

High levels of LDL cholesterol in the bloodstream can be the result of familial hypercholesterolemia, an inherited condition that displays incomplete dominance. In a family with a severely affected father and an unaffected mother, what percentage of their children are expected to have higher than normal blood cholesterol? A. 0% B. 25% C. 50% D. 100%

D, 100%

Flower color in snapdragons is an example of incomplete dominance. If 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 expected progeny plants will be __________. A. 100% pink B. 100% red C. 50% pink and 50% red D. 25% red, 50% pink, and 25% white

D, 25% red, 50% pink, and 25% white

In breeding pure-breeding large and small strains of mice, you cross individuals of each strain and note that their offspring are intermediate in size. Two models (explanations) to account for this result are (1) that body size in these strains is due to one gene with alleles that show incomplete dominance and (2) that body size is a polygenic trait. How could you distinguish between these models? A. Intercross the F1 and see if there is a range of sizes in the F2 (consistent with the incomplete dominance model) or if the F2 contains two size classes (consistent with the polygenic model). B. Intercross the F1 and see if there is a range of sizes in the F2 (consistent with the incomplete dominance model) or if the F2 contains only three size classes (consistent with the polygenic model). C. Body size is known to be an incompletely dominant trait. D. Intercross the F1 and see if the F2 contains three size classes (consistent with the incomplete dominance model) or if there is a range of sizes (consistent with the polygenic model).

D, Intercross the F1 and see if the F2 contains three size classes (consistent with the incomplete dominance model) or if there is a range of sizes (consistent with the polygenic model).

Which of the following statements regarding sickle-cell disease is false? A. Persons who are heterozygous for sickle-cell disease are also resistant to malaria. B. About one in 10 African Americans is a carrier of sickle-cell disease. C. All of the symptoms of sickle-cell disease result from the actions of just one allele. D. Sickle-cell disease causes white blood cells to be sickle-shaped.

D, Sickle-cell disease causes white blood cells to be sickle-shaped.

In a particular species of mammal, black hair (B) is dominant to green hair (b), and red eyes (R) are dominant to white eyes (r). When a BbRr individual is mated with a bbrr individual, offspring are produced in a ratio of 5 black hair and red eyes : 5 green hair and white eyes : 1 black hair and white eyes : 1 green hair and red eyes. Which of these explanations accounts for this ratio? A. The genes for hair color and the genes for eye color are carried on different chromosomes. B. The expected results did not take genetic recombination into account. C. Green-haired individuals have a higher prenatal mortality than black-haired individuals. D. The genes for hair color and eye color are linked.

D, The genes for hair color and eye color are linked.

Tay-Sachs disease runs in Rebecca's family. On a family pedigree, she saw a shaded circle. This represented: A. a female carrier B. a male with Tay-Sachs C. a male carrier D. a female with Tay-Sachs

D, a female with Tay-Sachs

Previously, it was thought that the blending hypothesis explained inheritance. The blending hypothesis maintained that __________. A. the characters governed by genes in the egg are different from the characters governed by genes in the sperm B. many genes are lost in their transmission to offspring, but the remaining genes gradually reproduce the lost genes C. mutation is the major source of new gene combinations D. after a mating, genes of the two parents are mixed in the offspring and lose their individual identities

D, after a mating, genes of the two parents are mixed in the offspring and lose their individual identities

The crossover percentage between two different genes is _____. A. dependent on the sex of the parent B. greater as the distance between the two genes decreases C. dependent on whether dominant or recessive alleles are carried by the two genes D. greater as the distance between the two genes increases

D, greater as the distance between the two genes increases

A carrier of a genetic disorder who does not show symptoms is most likely to be ________ to transmit it to offspring. A. heterozygous for the trait and unable B. homozygous for the trait and able C. homozygous for the trait and unable D. heterozygous for the trait and able

D, 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. A. dominant B. recessive C. co-dominant D. incompletely dominant

D, incompletely dominant

Our understanding of the role played by genes in many human characteristics is advancing rapidly in, for example, body size, performance on IQ tests, and personality traits. In this new genetic era, the role of the environment __________. A. is always far more important than genes in the development of complex human traits B. can largely be discounted in the development of complex human traits C. is important only in influencing personality traits D. is to work with genes in complex and often unknown ways in the development of these traits

D, is to work with genes in complex and often unknown ways in the development of these traits

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? A. co-dominance B. pleiotropy C. incomplete dominance D. polygenic inheritance

D, polygenic inheritance

Crossing over ________ genes into assortments of ________ not found in the parents. A. combines linked; genes B. recombines unlinked; genes C. combines unlinked; alleles D. recombines linked; alleles

D, recombines linked; alleles

Which of the following kinds of data could be used to map the relative position of three genes on a chromosome? A. the frequencies of mutations in the genes B. the frequencies with which the genes exhibit incomplete dominance over each other C. the frequencies with which the genes are inherited from the mother and from the father D. the frequencies with which the corresponding traits occur together in offspring

D, the frequencies with which the corresponding traits occur together in offspring

Imagine that a deaf male has a child with a hearing female. You know that the male must have the genotype dd, but the female could be either Dd or DD. If the couple's first child has hearing, can you determine the mother's genotype?

Her genotype cannot be determined.

John and Jane are planning a family, but since each has a brother who has sickle-cell disease, they are concerned that their children may develop sickle-cell disease. Neither John, Jane, nor their respective parents have the disease. They consult a genetic counselor who tells them that___?

It's possible that none of their children will have the disease, but blood tests on them both will be required to make sure.

A large and increasing number of genetic tests are available to prospective parents and children. Even as these testing methods become more and more sophisticated, what is one thing technology will never solve?

the ability to prescribe the correct course of action based on test results

Many genetic disorders can be detected before birth. Procedures include _____, which is noninvasive, or _____, which allows the chromosomes of the fetus to be examined. Alternatively, maternal blood samples can be taken and tested for _____.

ultrasound imaging, chorionic villus sampling , and AFP