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Mastering Biology Chapter 9
a ____ is an inherited feature that varies from individual to individual - character a ____ is one particular variation of a charater - trait a genetic cross involving parents that differ in a single character is called a - monohybrid cross Most human genes come in alternate versions called - alleles if an organism has two non-identical versions of a gene, the one that is expressed in the organism is called the ____ allele. - dominant if an organism has two non-identical versions of a gene, the one that is not expressed in the organism is called the ____ allele. - recessive the physical traits of an organism are called its - phenotype the ____ is the genetic makeup of an organism - genotype what is the genotype of the parent with orange eyes and white skin? orange eyes are recessive a) BbGg b) bbgg c) bbGG d) bbGg e) BBGG - b) bbgg Black eyes are dominant to orange eyes, and green skin is dominant to white skin. Sam, a MendAlien with black eyes and green skin, has a parent with orange eyes and white skin. Carole is a MendAlien with orange eyes and white skin. If Sam and Carole were to mate, the predicted phenotypic ratio of their offspring would be _____. a) 1 black eyes, green skin : 3 black eyes, white skin : 3 orange eyes, green skin : 9 orange eyes, white skin b) 3 black eyes, green skin : 3 black eyes, white skin : 9 orange eyes, green skin : 1 orange eyes, white skin c) 9 black eyes, green skin : 3 black eyes, white skin : 3 orange eyes, green skin : 1 orange eyes, white skin
d) 1 black eyes, green skin : 1 black eyes, white skin : 1 orange eyes, green skin : 1 orange eyes, white skin e) There is insufficient information to determine Sam's genotype. - d) 1 black eyes, green skin : 1 black eyes, white skin : 1 orange eyes, green skin : 1 orange eyes, white skin In order to determine the genotype of a MendAlien with black eyes and green skin, you would cross this individual with a(n) ____ individual. a) bbgg b) BbGg c) BBgg d) bbGG e) BBGG - a) bbgg (homozygous recessive) A cross between two individuals with black eyes and green skin which results in an individual with orange eyes and white skin is an example of a _____ cross. a) monohybrid b) dihybrid c) trihybrid d) difficult e) test - b) dihybrid A phenotypic ratio of 9:3:3:1 in the offspring of a cross indicates that _____. a) one parent is homozygous dominant and one parent is heterozygous b) one parent is heterozygous and one parent is homozygous recessive c) both parents are homozygous dominant d) both parents are heterozygous for both genes e) one parent is homozygous dominant and one parent is homozygous recessive - d) both parents are heterozygous for both genes The observed distribution of alleles into gametes is an illustration of _____. a) Mendel's law of independent assortment only b) Mendel's law of segregation only c) Thienemann's rule d) Eimer's principle e) Mendel's law of segregation and independent assortment - e) Mendel's law of segregation and independent assortment An individual heterozygous for eye color, skin color, and number of eyes mates with an individual who is homozygous recessive for all three characters; what would be the expected phenotypic ratio of their offspring? [Hint: B = black eyes, b = orange eyes; G = green skin, g = white skin; C = two eyes, c = one eye] a) 9 orange eyes, green skin, two eyes : 9 orange eyes, green skin, one eye : 9 orange eyes, white skin, two eyes : 1 orange eyes, white skin, one eye b) 1 black eyes, green skin, two eyes : 1 black eyes, green skin, one eye : 1 black eyes, white skin, two eyes : 1 orange eyes, green skin, two eyes : 1 orange eyes, white skin, two eyes : 1 orange eyes, white skin, one eye
a) particles that travel throughout the body, capturing particular characteristics, before the particles ultimately come to reside in sperm and eggs for transmission to the next generation b) unblendable heritable factors that were contributed by each parent and never altered by mixing c) segments of DNA (genes) that encode proteins, which ultimately control traits of the offspring d) a blending of heritable factors in offspring, much as a combination of blue and red pigments produces purple color - b) unblendable heritable factors that were contributed by each parent and never altered by mixing When applied to Mendel's experiments, the term true-breeding means a self-fertilization of two plants that produces __________. a) offspring identical to the parent b) offspring with blended traits c) offspring with only dominant traits d) offspring with only recessive traits - a) offspring identical to the parent In a monohybrid cross, F2 refers to ____. a) the original mating pair b) the grandparents of the 1st generation c) the 1st filial generation d) the second filial generation, or the "grandchildren" of the original mating pair - d) the second filial generation, or the "grandchildren" of the original mating pair The cross-fertilization of two different, but true-breeding, varieties of pea plants will _____. a) produce an F2 generation b) yield the P generation c) result in hybrid plants d) be lethal - c) result in hybrid plants In a standard monohybrid cross between purple-flowered and white-flowered peas, in which purple flowers are dominant, what fraction of the purple-flowered peas in the F2 generation would you expect to be true-breeding? a) 1/ b) 1/ c) 1/ d) 1/2 - c) 1/ An insect that has the genotype EeGGcc will have the same phenotype as an insect with the genotype __________. a) EEGgcc b) eeggcc c) EEGGCc d) EEggcc - a) EEGgcc
Assume that in cattle a spotted coat is dominant to an even coat, short horns are dominant to long horns, and the traits for coat type and horn length assort independently. In a cross between cattle that are each heterozygous for both traits, what proportion of their offspring are expected to have long horns? a) 1/ b) 3/ c) 1/ d) 9/16 - c) 1/ 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 × PpRr are expected to have white flowers and wrinkled seeds? a) 1/ b) 3/ c) 9/ d) 12/16 or 3/4 - a) 1/ Imagine that long fins in zebrafish is a dominant trait. A breeder wants to set up a breeding program beginning with homozygous dominant long-finned fish. If she obtains a handful of the long-finned fish, how can she tell which, if any, of these are homozygous for the trait? a) Cross the long-finned fish with short-finned fish; unless all of the offspring are short- finned, the long-finned parent is homozygous b) Cross the long-finned fish with short-finned fish; if the offspring are all long-finned, the long-finned parent is homozygous c) Cross the long-finned fish with short-finned fish; if three-fourths of the offspring are long- finned and one-fourth are short-finned, the long-finned parent is homozygous d) Cross the long-finned fish with short-finned fish; if four-fifths of the offspring are long- finned and one-fifth are short-finned, the long-finned parent is homozygous - b) Cross the long-finned fish with short-finned fish; if the offspring are all long- finned, the long-finned parent is homozygous 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 the offspring trees produce big red apples and half produce big yellow apples. What are the genotypes of the parents? A = big apples; a = small apples; R = red apples; r = yellow apples. a) AaRr and AaRr b) Aarr and aaRr c) AARr and AArr d) AArr and aaRr - d) AArr and aaRr Three characteristics assort independently in one species of insect: Red eyes (R) are dominant to black eyes (r). Blue wings (B) are dominant to white wings (b). Green bodies (G) are dominant to yellow bodies (g). A cross is made between two heterozygous insects (RrBbGg). What is the probability that the offspring will be homozygous dominant for all three characteristics? a) 1/ b) 1/
b) Less is known about lethal dominant disorders, so the rareness of these alleles is an artifact due to a lack of detection. c) The types of mutations that create lethal dominant alleles are much less frequent than those that create lethal recessive alleles. d) The lethality associated with lethal dominant alleles is much more severe than that associated with lethal recessive alleles. - a) Lethal dominant alleles are harmful whether they are carried in homozygous or heterozygous form, so there is always strong selection against these alleles. 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, there is a 50% chance that the child will have Tay-Sachs disease. b) They should be informed that if they conceive a child, the child will have Tay-Sachs disease. c) 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. d) They should be informed that if they have a child, there is a 25% chance that the child will have Tay-Sachs disease. - c) 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. John and Jane are planning a family, but each has a brother who has sickle-cell disease, so they are concerned that their children may develop sickle-cell disease. Neither John nor Jane nor their respective parents have the disease. They consult a genetic counselor who tells them that __________. a) one of four of their children can be expected to have sickle-cell disease b) all of their children will have sickle-cell disease c) it's possible that they cannot produce a child with sickle-cell disease, but blood tests on them both will be required to make sure d) there is no chance that any of their children will have sickle-cell disease - c) it's possible that they cannot produce a child with sickle-cell disease, but blood tests on them both will be required to make sure Akin to urban legends, there are curious genetics legends - things like eye color being determined by one gene, with a brown eye allele being completely dominant to blue. The problem comes when simple myth meets the complex reality of how eye color and many other traits are transmitted. Why is the inheritance of so many traits difficult to explain using only Mendel's view of genetics? a) Mendel's laws of segregation and independent assortment apply only in a limited set of cases in sexually reproducing organisms. b) Failures in the predictive power of Mendel's ideas about inheritance are artifacts that reflect our incomplete understanding of the organisms under study. c) Mendel worked with peas, not humans, and the genetic principles that operate in a simple organism such as a pea plant cannot be applied to an organism as complex as a human. d) Mendel was correct for the traits he investigated, but his principles mus - d) Mendel was correct for the traits he investigated, but his principles must be extended (not discarded) to explain many more complex patterns of inheritance.
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% If one parent is blood type AB and the other is type O, what fraction of their offspring is expected to have blood type A? a) 0 b) 0. c) 0. d) 1.0 - b) 0. In 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 pleiotropic effects of the sickle-cell allele b) the polygenic nature of sickle-cell disease c) a bacterial infection interacting with the sickle-cell allele d) side effects of the drugs used to treat sickle-cell disease - a) the pleiotropic effects of the sickle-cell allele 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) Body size is known to be an incompletely dominant trait. c) 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). d) Intercross the F1 and see if the F2 contains three size classes (cons - 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). Two identical twins are raised in different environments. They possess _____ genotypes and _____ phenotypes. a) identical...variable b) identical...dissimilar c) identical...identical
The existence of rare XY individuals who are phenotypically normal women was instrumental in learning about human sex determination. Maleness is determined by the SRY gene found on the Y chromosome. How is it possible to be both XY and phenotypically female? a) A portion of the Y chromosome containing SRY is duplicated. b) The SRY locus of the Y chromosome has translocated (moved) to an autosome (a chromosome other than a sex chromosome). c) The SRY locus changed position on the Y chromosome d) The SRY locus of the Y chromosome is deleted. - d) The SRY locus of the Y chromosome is deleted. Hemophilia is caused by a sex-linked recessive gene. I am sure that I do not have hemophilia. What genotype must I be? a) X^H, Y^H b) X^h, Y^ c) X^H, Y^ d) X^H, Y^h e) we cannot say for sure - c) X^H, Y^ Consider the hypothetical sex linked recessive baldness gene. If a bald woman has a child with a normal male, what are the odds that their son will be bald? a) 0% b) 25% c) 50% d) 100% e) the answer cannot be determined from the information given - d) 100%
- bc the mom's X is the only X he is getting so he automatically has it. A woman who is a carrier of hemophilia marries a man affected with hemophilia. What percentage of their sons and daughters is expected to have hemophilia? a) 100% of sons and 50% of daughters b) 0% of sons and 50% of daughters c) 50% of sons and 0% of daughters d) 50% of sons and 50% of daughters - d) 50% of sons and 50% of daughters We can better understand our ancestry by analyzing the __________ in males. a) Y chromosome b) gene for SRY c) X chromosome d) gene for colorblindness - a) Y chromosome 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 _____. a) ultrasound imaging ... chorionic villus sampling ... AFP
b) ultrasound imaging ... AFP ... amniocentesis c) amniocentesis ... AFP ... chorionic villus sampling d) amniocentesis ... ultrasound imaging ... chorionic villus sampling - a) ultrasound imaging ... chorionic villus sampling ... AFP There are over 100 alleles known for the gene associated with cystic fibrosis. With current technology, it is possible to determine exactly which allele or alleles is/are carried by a person. What is the maximum number of different alleles that any person can carry? a) 2 b) 1 c) 16 d) as many as there are alleles of the gene (~ 100 in this case) - a) 2 Two parents of mixed ethnicity have twins, one of which is born with very light skin and one of which is born with very dark skin. This is because of __________. a) the pleiotropic effects of skin color genes b) the inheritance of two linked skin color genes c) the polygenic nature of skin color genes d) exposure to sunlight - c) the polygenic nature of skin color genes 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 important only in influencing personality traits b) is to work with genes in complex and often unknown ways in the development of these traits c) can largely be discounted in the development of complex human traits d) is always far more important than genes in the development of complex human traits - b) is to work with genes in complex and often unknown ways in the development of these traits In corn, blue kernels are produced by a dominant allele of a coloration gene, and white kernels are produced in individuals homozygous for a recessive allele of the same coloration gene. Another gene has two alleles for shape, with smooth kernels being dominant to wrinkled. A plant heterozygous for both genes is test-crossed (crossed to a homozygous recessive white, wrinkled strain). The test-cross offspring consist of the following types: 1,447 blue smooth; 1,436 white wrinkled; 150 blue wrinkled; 145 white smooth. Explain the inheritance of the coloration and shape traits. a) Neither the coloration nor the shape genes are segregating. b) Only the coloration gene segregates properly; the shape gene fails to segregate c) The coloration and shape genes are linked on the same chromosome. d) The shape and coloration genes assort independently. - c) The coloration and shape genes are linked on the same chromosome. The Y chromosomes of mammals contain genes that code for _____. a) both eye pigment and blood-clotting factor, among many other characters b) "maleness" and a few other characteristics c) eye pigment, among many other characters
