Tay-Sachs disease runs in Rebecca’s family. On a family pedigree, she saw a shaded circle. This represented: |
D, a female with Tay-Sachs |
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. |
Her genotype cannot be determined. |
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. |
Most people afflicted with recessive disorders are born to parents who were |
A, not at all affected by the disease |
Most genetic disorders of humans are caused by A. a mutation that occurs in the egg, sperm, or zygote. |
C, recessive alleles |
A carrier of a genetic disorder who does not show symptoms is most likely to be ________ to transmit it to offspring. |
D, heterozygous for the trait and able |
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. |
Human genetic disorders _____. |
C, are most often recessive |
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. |
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 |
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 |
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? |
B, 0.5 |
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? |
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 __________. |
D, 25% red, 50% pink, and 25% white |
Which of the following is an example of incomplete dominance in humans? |
A, hypercholesterolemia |
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. |
D, incompletely dominant |
For most sexually reproducing organisms, Mendel’s laws |
C, help us understand the global geographic patterns of genetic disease. |
Snapdragons show incomplete dominance in their flowers. A pink snapdragon is crossed with a red snapdragon. What color(s) are the offspring? |
B, 50% red, 50% pink |
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? |
C, 0% |
A person with AB blood illustrates the principle of |
A, co-dominance |
The expression of both alleles for a trait in a heterozygous individual illustrates |
A, co-dominance. |
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? |
C, IA i x IA IB |
Sickle-cell disease is an example of |
C, co-dominance and pleiotropy. |
Which of the following statements regarding sickle-cell disease is false? |
D, Sickle-cell disease causes white blood cells to be sickle-shaped. |
Which of the following statements is false? |
C, ABO blood groups can provide evidence of paternity. |
A single allele that controls more than one character is said to be _____. |
C, pleiotropic |
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 __________. |
C, the pleiotropic effects of the sickle-cell allele |
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? |
B, pleiotropy |
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? |
D, polygenic inheritance |
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? |
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 parents of mixed ethnicity have twins, one of which is born white and one of which is born black. This is because of _____. |
B, the polygenic nature of skin color genes |
The inheritance of height and weight can best be described as __________. |
C, polygenic and multifactorial |
Two identical twins are raised in different environments. They possess _____ genotypes and _____ phenotypes. |
C, identical … variable |
The individual features of all organisms are the result of |
A, genetics and the environment. |
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 __________. |
D, is to work with genes in complex and often unknown ways in the development of these traits |
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. |
The chromosome theory of inheritance states that |
C, the behavior of chromosomes during meiosis and fertilization accounts for patterns of inheritance. |
The chromosome theory of inheritance is based upon which of the following sets of observations? |
A, Genes segregate; chromosomes come in pairs. |
You conduct a dihybrid cross. A ________ ratio would make you suspect that the genes are linked. |
B, 12:1:1:4 |
Linked genes generally |
… |
Linked genes generally |
C, do not follow the laws of independent assortment. |
Genes located close together on the same chromosomes are referred to as ________ genes and generally ________. |
A, linked; do not sort independently during meiosis |
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 |
Linked genes are inherited together. This is because linked genes _____. |
C, are on the same chromosome |
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? |
D, The genes for hair color and eye color are linked. |
The mechanism that "breaks" the linkage between linked genes is |
C, crossing over. |
Crossing over ________ genes into assortments of ________ not found in the parents. |
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? |
D, the frequencies with which the corresponding traits occur together in offspring |
Sturtevant’s genetic mapping _____. |
C, orders genes on a chromosome based on recombination frequencies |
The crossover percentage between two different genes is _____. |
D, greater as the distance between the two genes increases |
Previously, it was thought that the blending hypothesis explained inheritance. The blending hypothesis maintained that __________. |
D, after a mating, genes of the two parents are mixed in the offspring and lose their individual identities |
Biology notes Ch. 9
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