Chapter 3
Albinism, lack of pigmentation in humans, results from an autosomal recessive gene. Two parents with normal pigmentation have an albino child. What is the probability that their next two children will be albino? A. 1/16 B. 1/2 C. 1/3 D. 3/4
A. 1/16
Which phenotypic ratio is likely to occur in crosses of two completely dominant, independently segregating gene pairs when both parents are fully heterozygous? A. 9:3:3:1 B. 2:4:6:8 C. 1:1:1:1 D. 3:2:3:1
A. 9:3:3:1
A cross between two individuals with different phenotypes that resulted in approximately 50% of each type of offspring would indicate the cross was ________. A. a heterozygous dominant crossed to a homozygous recessive B. true breeding dominant to recessive C. a homozygous recessive crossed to a heterozygous recessive D. a heterozygous dominant crossed to a heterozygous recessive
A. a heterozygous dominant crossed to a homozygous recessive
What conditions are likely to apply if the progeny from the cross AaBb×AaBb appear in the 9:3:3:1 ratio? A. complete dominance, independent assortment, and no gene interaction B. incomplete segregation and complete dominance C. gene interaction and independent assortment D. dihybrid cross with incomplete dominance
A. complete dominance, independent assortment, and no gene interaction
Assuming independent assortment, what proportion of the offspring of the cross AaBbCcDd × AabbCCdd will have the aabbccdd genotype? A. 1/64 B. 0 C. 1/256 D. 1/512
B. 0
Polydactyly is expressed when an individual has extra fingers and/or toes, and is transmitted via an autosomal dominant allele. Assume that a man with six fingers on each hand and six toes on each foot marries a woman with a normal number of digits. The couple has a son with normal hands and feet, but the couple's second child has extra digits. What is the probability that their next child will have polydactyly? A. 1/8 B. 1/2 C. 3/4 D. 7/16
B. 1/2
Assuming a typical monohybrid cross in which one allele is completely dominant to the other, what phenotypic ratio is expected if the F1s are crossed? A. 2:1 B. 3:1 C. 3:2 D. 1:1
B. 3:1
Mendel indicated that traits were made up of unit factors. Today, we call unit factors ________. A. genes B. alleles C. characters D. genotypes
B. alleles
Mendel crossed two pea plants with round seeds. All seeds of the offspring were round. He then crossed a plant with round seeds to a plant with wrinkled seeds and all offspring had wrinkled seeds. Which of the following is true? A. round is dominant B. wrinkled is dominant C. the plants he used were not true-breeding D. a mutation occurred
B. wrinkled is dominant
A recessive allele in dogs causes white spots. If two solid colored dogs are mated and produce a spotted offspring, what is the percentage chance their next puppy would be solid colored? A. 50% B. about 90% C. 75% D. 25%
C. 75%
What is segregation? A. Fertilization is random. B. During gamete formation, segregating pairs of unit factors assort independently of each other. C. During gamete formation, allele pairs are separated to form haploid gametes. D. Chromosomes can swap information during meiosis.
C. During gamete formation, allele pairs are separated to form haploid gametes.
Which of the following describes the product law? A. The product of the sum of the probabilities of two simultaneous events describes the ability of those two events to occur together. B. The probably of two linked events occurring simultaneously is equal to the probabilities of each individual event. C. The probability of two or more independent events occurring simultaneously is equal to the product of their individual probabilities. D. The probability of two or more independent events occurring simultaneously is equal to the sum of their individual probabilities.
C. The probability of two or more independent events occurring simultaneously is equal to the product of their individual probabilities.
The autosomal (not X-linked) gene for brachydactyly, short fingers, is dominant to normal finger length. Assume that a female with brachydactyly in the heterozygous condition is married to a man with normal fingers. What is the probability that their first child will have brachydactyly? A. 1/4 B. 1/8 C. 3/4 D. 1/2
D. 1/2
Tightly curled or wooly hair is caused by a dominant gene in humans. If a heterozygous curly-haired person marries a person with straight hair, what percentage of their offspring would be expected to have straight hair? A. 0% B. 25% C. 75% D. 50%
D. 50%
How many different possible gametes can be obtained from an organism with the following genotype AaBbCc? A. 16 B. 9 C. 4 D. 8
D. 8
If an F2 generation from an F1 self-cross always yields offspring in a 3:1 phenotypic ratio, which of the following P crosses could have occurred? A. AA × AA B. aa × Aa C. Aa × AA D. AA × aa
D. AA × aa
A certain type of congenital deafness in humans is caused by a rare autosomal dominant gene. In a mating involving a deaf man and a deaf woman, could all the children have normal hearing? A. No, because children favor their parents. B. Yes, because traits assort independently. C. No, because it is dominant. Children always get the dominant alleles. D. Yes, assuming that the parents are heterozygotes (because the gene is rare), it is possible that all of the children could have normal hearing.
D. Yes, assuming that the parents are heterozygotes (because the gene is rare), it is possible that all of the children could have normal hearing.
Mendel utilized the garden pea, Pisum sativumfor his studies based on features that include all but ________. A. can generate a large number of progeny B. easy to grow C. reaches maturity in a single season D. has visible features with a wide spectrum of intermediates
D. has visible features with a wide spectrum of intermediates
The physical expression of a trait is referred to as a(n) ________. A. allele B. genotype C. gene D. phenotype
D. phenotype
The process that leads to the development of haploid gametes is best described as ________. A. replication B. independent assortment C. Mendelian inheritance D. segregation
D. segregation