Ch 14, 22, Review Answers rev 11/14/02
1 A 9 purple to 7 white phenotype in sweetpeas in the F2 generation is due to epistasis
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
3 Effects of this recessive single gene can be completely overcome by regulating the diet of the affected individual. 3
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
5 Individuals with this disorder are unable to metabolize gangliosides, which affects proper brain development. Affected individuals die in early infancy. 2
6 Substitution of the "wrong" amino acid in the hemoglobin protein results in this disorder. 5
7 A man is brought to court in a paternity case. The alleged father has blood group B, Rh positive. The mother has blood group A, Rh negative. Which blood group of the child will exclude the alleged father from possible paternity? None of these choices will exclude the man from possible paternity.
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
9 Which of the following statements is true regarding genomic imprinting? (A) It explains cases where the gender of the parent from whom an allele is inherited affects the expression of that allele.(B) It is greatest in females because of the larger maternal contribution of cytoplasm. (C) It may explain the transmission of Duchenne's muscular dystrophy. (D) It explains sex-linked inheritance in which the sex of the parent carrying the mutant allele determines whether male or female offspring will be affected. (E) It is found in X-inactivation in human females during early embryonic development.
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.
11 The following is a list of chromosomal alterations. Which one of these would automatically cause two of the others?. nonreciprocal translocation
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.
13 Fragile-x syndrome is more common in males than in females. One explanation for this is genomic imprinting by the mother.
14 What do all males inherit from their mother? mitochondrial DNA and X chromosome
15 A mammalian zygote with which of the following chromosomal abnormalities will NEVER develop into a viable embryo? YO
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.
17 What does independent assortment refer to? . the random arrangement of chromosomal tetrads at metaphase I
18 A Barr body (sex chromatin) is normally found in the nucleus of which kind of human cell? somatic cells of a female only
19 Which of the following is associated with being a metafemale? an extra sex chromosome
20 The particular position of a gene on a chromosome is known as a(n) locus
21 The frequency of crossing over between any two linked genes is proportional to the distance between them.
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%
23 A man who carries an X-linked allele will pass it on to all of his daughters.
24 Down syndrome may be caused by three copies of chromosome 21.and a translocation involving chromosomes 15 and 21.
25 Which of the following is a sex-influenced trait? male-pattern baldness
26 Which of these syndromes afflicts males only? Duchenne's muscular dystrophy
27 Thomas Hunt Morgan is best remembered for his discovery and explanation of sex-linkage
28 There is good evidence for linkage when genes located on two different loci do not segregate independently during meiosis..T
29 If a pair of homologous chromosomes fail to separate during anaphase of meiosis I, what will be the chromosomes number (N) of the four resulting gametes? N+1; N+1; N1; N1
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%
31 A man is brought to court in a paternity case. The alleged father has blood group B, Rh positive. The mother has blood group A, Rh negative. Which blood group of the child will exclude the alleged father from possible paternity? none
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
33. Kleinefelter's syndrome results from a zygote having XXY
34. Failure of chromosomes to separate during meiosis.is nondisjunction
35 If a normal human egg is fertilized by a sperm lacking the sex chromosome, the offspring will show a combination of defects known as Turner syndrome
36. The inheritance of the ABO blood type in humans is an example of multiple alleles
ch 21 Web Extras from handout
37 All of the following are facts or inferences of natural selection there is heritable variation among individuals, since only a fraction of offspring survive, there is a struggle for limited resources. , individuals whose inherited characteristics best fit them to the environment will leave more offspring. ,unequal reproductive success leads to adaptations.
38 The gene pool can best be described as the total aggregate of genes in a population at any time.
39 What may cause a gene pool to move and shift randomly and by chance? genetic drift
40 Through time the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing gene flow.
41 Natural selection is most closely related to differential reproductive success.
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
43 Which of the following is one important evolutionary feature of the diploid condition? Diploid organisms express less of their genetic variability than haploid organisms.
44 Natural selection tends to reduce variation in gene pools. Which process serves to balance natural selection by creating new alleles? mutation
45 What can cause change in allelic frequencies due to an influx of new members into a population? gene flow
46. Cattle breeders have improved the quality of meat over the years by which process? artificial selection