Ch 14, 22, Review Answers rev 11/14/02
2 The probability that four coins will come up heads when flipped simultaneously is 1/16 (0.062)
Use the choices shown below to answer the following question(s). Each choice may be used once, more than once, or not at all.
1. Huntington's disease
2. Tay-Sachs disease
3. phenylketonuria
4. hemophilia
5. sickle-cell anemia
4 This is caused by a dominant single gene defect and generally does not appear until the individual is 30-40 years of age. 1
6 Substitution of the "wrong" amino acid in the hemoglobin protein results in this disorder. 5
8 In a dihybrid cross, the expected proportion of offspring showing both recessive traits is 1/16 B In a cross between parents who both exhibit the dominant curly- anddark-haired traits, one child has straight, light-colored hair. What is the hair genotype of the parents? CcDd x CcDd E In a cross AaBbCc x AaBbCc, what is the probability of producing the genotype AABBCC? 1/64
10 If inheritance of a human trait is sex-linked (on the X chromosome) and recessive, any of the following could result EXCEPT that the trait could be more common in females than males.
12 The finding that defective genes behave differently in offspringdepending on whether they belong to the maternal or paternal chromosome is implicated in which of the following? 1. Prader-Willi syndrome 2. Fragile-X syndrome 3. Angleman syndrome.
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14 What do all males inherit from their mother? mitochondrial DNA and X chromosome
16 All of the following statements are true about chromosomal inversions They involve breakage of a chromosome. - They do not change the normal balance of genes. - They change the order of the genes on the chromosome. -They involve the rearrangement of the genes.
18 A Barr body (sex chromatin) is normally found in the nucleus of which kind of human cell? somatic cells of a female only
20 The particular position of a gene on a chromosome is known as a(n) locus
22 A recessive allele on the X chromosome is responsible for red-green color blindness in humans. A normal vision woman whose father is color-blind marries a color-blind male. What is the probability that this couple's son will be color-blind? 50%
24 Down syndrome may be caused by three copies of chromosome 21.and a translocation involving chromosomes 15 and 21.
26 Which of these syndromes afflicts males only? Duchenne's muscular dystrophy
28 There is good
evidence for linkage when genes located on two different loci do not segregate
independently during meiosis..T
30 In humans,
male-pattern baldness is controlled by a gene that occurs in two allelic forms.
Allele Hn determines nonbaldness and allele Hb determines pattern baldness. The
interaction of these two alleles in the heterozygote condition is of special
interest because in the presence of male hormone allele Hn is dominant over Hb.
If a man and woman both with genotype Hn/Hb have many children, approximately
what percentage of their male children would be expected to eventually be bald?
75%
32 Beard is a trait in humans that ordinarily expresses in males only. With just this information available, which of the following could explain how beard is inherited in humans? beard is a sex limited trait
34. Failure of chromosomes to separate during meiosis.is nondisjunction
36. The inheritance of the ABO blood type in humans is an example of multiple alleles
ch 21 Web Extras from handout
38 The gene pool can best be described as the total aggregate of genes in a population at any time.
40 Through time the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing gene flow.
42 In 1989 an earthquake in Armenia killed a significant portion of the population. Which of the following may occur in the population as a result of the earthquake? bottleneck effect
44 Natural selection tends to reduce variation in gene pools. Which process serves to balance natural selection by creating new alleles? mutation
46. Cattle breeders have improved the quality of meat over the years by which process? artificial selection
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