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30 Cards in this Set

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  • Back
Jean Baptiste Lamarck proposed an early theory of evolution that was based on the inheritance of acquired characteristics. According to Lamarck, if an individual acquired a particular characteristic—such as flexibility from stretching or great strength from heavy exercise—these characteristics would be transmitted to the organism's offspring. This same idea of transmission of an acquired character from parent to offspring is also part of a more ancient idea, the idea of _____. (Module 9.1)
Mendel's view of the mechanism of heredity was radically different from the prevailing view of the time because he saw heredity working through _____. (Module 9.2)
unchanging (immutable), heritable factors that were contributed by each parent and never mixed
Two mice are crossed. Matings are carried out between the offspring of these mice to produce "grandchildren" of the original mated pair. In the standard terminology of genetics, the "grandchildren" are the _____. (Module 9.2)
F2 generation
True-breeding individuals differing in a single character, say a pea plant bearing green seeds and another bearing yellow seeds, are crossed. Assuming that this trait is determined by a single gene that is present in two forms (yellow and green, in this case), how can you tell which allele is dominant and which is recessive? (Module 9.3)
Observe the trait expressed by the F1 plants.
Mendel was a meticulous experimentalist. One set of crosses he performed to test his idea that a pair of hereditary determinants segregated into gametes was to allow self-fertilization of F2 individuals to produce F3 offspring. What proportion of the purple-flowered F2 individuals did Mendel predict to be true-breeding? (Module 9.3)
In an individual of genotype Aa, where are the A and a alleles physically located? (Module 9.4)
One allele is on one chromosome, and the other is in the same position (locus) on the homologous chromosome.
Mendel's principle of independent assortment applies to the _____. (Module 9.5)
independent assortment of alleles of one gene relative to the alleles of any other gene
Assume that in cattle spotted coat is dominant to 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 is expected to have long horns? (Module 9.5)
Imagine that long fins in zebra fish 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 rare long-finned fish, how can she tell which if any of these are homozygous for the trait? (Module 9.6)
Cross the long-finned fish with short-finned fish; if the offspring are all long-finned, the long-finned parent is homozygous.
In Labrador dogs, black coat is dominant to chocolate, normal vision is dominant to progressive retinal atrophy (PRA), and normal hip joint is dominant to hip dysplasia. All these genes assort independently. Two dogs that are heterozygous for alleles of all three genes are crossed. Using rules of probability (not a Punnett square), what is the chance that the first pup born to these dogs will be chocolate, have normal vision, and have normal hip joints? (Module 9.7)
Two normal parents have three normal children-one son and two daughters. Their son and one of their daughters marry and also have normal children. Their second daughter, Mary, marries a man with a rare, recessive blood disorder. They have two children, and both children develop the blood disorder. What were the genotypes of Mary's parents? (Module 9.8)
Either one of her parents or both of her parents were heterozygous for the trait.
Human genetic disorders _____. (Module 9.9)
are most often recessive
Why are lethal dominant alleles so much more rare than lethal recessive alleles? (Module 9.9)
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? (Module 9.10)
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 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? (Module 9.10)
the ability to prescribe the correct course of action based on test results
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? (Module 9.11)
Mendel was correct for the traits he investigated, but his principles must be extended (not discarded) to explain many more complex patterns of inheritance.
As described in the text, hypercholesterolemia is a disorder in which blood cholesterol levels are elevated. The H allele is incompletely dominant to the h allele, with hh homozygotes having extremely high levels of blood cholesterol. A husband and wife are both Hh heterozygotes. What is the chance that their first child will have normal levels of blood cholesterol? (Module 9.12)
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 are carried by a person. What is the maximum number of different alleles that any person can carry? (Module 9.13)
In lentils, the C gene has two different alleles. CSCS homozygotes have spotted seeds, CDCD homozygotes have dotted seeds, and CSCD heterozygotes have seeds with both spots and dots. This indicates that _____. (Module 9.13)
CS and CD are codominant
If the gene for seed color that Mendel studied exhibited pleiotropy, how might a green pea be different from a yellow pea? (Module 9.14)
With pleiotropy, there would be other differences between the peas-for example, green peas may also be larger, ripen earlier, and be more sensitive to frost.
Imagine you're working with 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? (Module 9.15)
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).
Our understanding of the role played by genes in many human characteristics—for example, body size, performance on IQ tests, and personality traits—is advancing rapidly. In this new genetic era, the role of the environment _____. (Module 9.16)
is to work with genes in complex and often unknown ways in the development of these traits
There is an explosion in the number of genetic tests that are becoming available. Today, it's possible to test an individual for hundreds of different genetic disorders or conditions. However, a concern among human geneticists is that _____. (Module 9.17)
for most people, testing without appropriate counseling is likely to do more harm than good
Which of the following line or lines of evidence support the chromosome theory of inheritance? (Module 9.18)
All these lines of evidence support the chromosome theory.
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 testcrossed (crossed to a homozygous recessive white, wrinkled strain). The testcross offspring consist of the following types: 1,447 blue smooth; 1,436 white wrinkled; 150 blue wrinkled; 145 yellow smooth. Explain the inheritance of the coloration and shape traits. (Module 9.19)
The coloration and shape genes are linked on the same chromosome.
In Morgan's testcross of a gray-bodied, long-winged heterozygous female Drosophila with a homozygous recessive black-bodied, vestigial-winged male, the following offspring were obtained: 965 gray body, long wing; 944 black body, vestigial wing; 206 gray body, vestigial wing; 185 black body, long wing. Focusing only on the recombinant classes (gray body, vestigial wing and black body, long wing), the numbers of offspring of each type are similar (206 and 185). What accounts for the similar number of offspring of each recombinant phenotype? (Module 9.20)
Crossing over between chromosomes is reciprocal, so whenever a recombinant chromosome of one type is produced, there's a recombinant of the opposite type that is also produced.
Imagine that a mutant strain of Drosophila undergoes crossing over at half the normal rate. How would a genetic map prepared for this mutant differ from a genetic map prepared for a normal (wild type) fly? (Module 9.21)
The order of genes would be the same in both strains, but the distances measured between genes in the mutant would be half that of the wild type.
The existence of rare XY individuals who are phenotypically normal women was instrumental in learning about human sex determination. How is it possible to be an XY woman? (Module 9.22)
The SRY locus of the Y chromosome is deleted
Vitamin D-resistant rickets is an X-linked dominant bone disorder. A man with this form of rickets marries a normal woman. What proportion of the couple's daughters is expected to have vitamin D-resistant rickets? (Module 9.23)
A woman who is a carrier of hemophilia marries a man affected with hemophilia. What percentage of their sons and daughters are expected to have hemophilia? (Module 9.24)
50% of sons and 50% of daughters