Name Class Date
SECTION 9-1 REVIEW
MENDEL’S LEGACY
VOCABULARY REVIEW Distinguish between the terms in each of the following pairs of terms.
1. F1 generation, F2 generation
2. dominant, recessive
3. self-pollination, cross-pollination
MULTIPLE CHOICE Write the correct letter in the blank.
1. Mendel obtained plants that were true-breeding for particular traits by
a. growing plants from the seeds of c. allowing plants to self-
other plants that showed that trait. pollinate for several
generations.
b. discarding plants that showed d. allowing plants to cross-
others traits. pollinate for one generation.
2. When Mendel crossed a strain of tall pea plants with a strain of short pea plants, he observed that all of the plants in the F1 generation were tall. This suggests that
a. the tall trait was controlled by a c. both traits were controlled by dominant factor. a recessive factor.
b. the short trait was controlled by a d. the strain of short plants was dominant factor. capable of pollinating the strain of tall plants.
3. A cross between true-breeding green-podded pea plants and true-breeding yellow-podded pea plants produces only green-podded plants. When the F1 generation is allowed to self-pollinate, the F2 generation consists of
a. only green-podded plants.
b. only yellow-podded plants.
c. about three-quarters yellow-podded plants and one-quarter green-podded plants.
d. about three-quarters green-podded plants and one-quarter yellow-podded plants.
4. When alleles for different characteristics are on separate chromosomes, they are distributed to gametes independently. This observation is summarized by the law of
a. cross-pollination. c. segregation.
b. independent assortment. d. molecular genetics.
SHORT ANSWER Answer the questions in the space provided.
1. What does the term allele mean as it is used in genetic crosses?
2. Explain how the events of meiosis account for the law of segregation and the law of independent assortment.
3. If orange flower color in a plant is controlled by an allele F and red flower color is controlled by an allele f, which flower color is dominant?
If true-breeding orange-flowered plants are crossed with true-breeding red-flowered plants, what will be the flower color(s) of the F1 plants?
4. Critical Thinking How would Mendel’s observations and conclusions have been different if many of the characteristics he studied, such as seed color and seed texture, had been controlled by genes located close together on the same chromosome?
STRUCTURES AND FUNCTIONS In the spaces inside each gamete, indicate the four possible combinations of alleles the gametes could receive.
The diagram below shows the assortment of two pairs of homologous chromosomes during meiosis. One pair has a gene for flower color (R allele = red, r allele = white). The other pair has a gene for seed color (B allele = brown, b allele = gray).
SECTION 9-2 REVIEW
GENETIC CROSSES
VOCABULARY REVIEW Define the following terms, and provide one example for each.
1. complete dominance
2. incomplete dominance
3. codominance
MULTIPLE CHOICE Write the correct letter in the blank.
1. The appearance of an organism is its
a. genotype. b. phenotype. c. genotypic ratio. d. phenotypic ratio.
2. A genetic cross performed many times produces 798 long-stemmed plants and 266 short-stemmed plants. The probability of obtaining a short-stemmed plant in a similar cross is
a. 266/1,064. b. 266/798. c. 798/266. d. 798/1,064.
3. A monohybrid cross of two individuals that are heterozygous for a trait exhibiting complete dominance would probably result in a phenotypic ratio of
a. 4 dominant:0 recessive. c. 3 dominant:1 recessive.
b. 1 dominant:3 recessive. d. 1 dominant:1 recessive.
4. To determine the genotype of an individual that shows the dominant phenotype, you would cross that individual with one that is
a. heterozygous dominant. c. homozygous dominant.
b. heterozygous recessive. d. homozygous recessive.
5. In a dihybrid cross between an individual with the genotype RRYY and an individual with the genotype rryy, all of the offspring will have the genotype
a. RRYY. b. RrYY. c. RrYy. d. rryy.
SHORT ANSWER Answer the questions in the space provided.
1. What is the difference between a homozygous individual and a heterozygous individual?
2. If the probability that a specific trait will appear in the generation is 0.25, how many individuals would be expected to show that trait in an generation consisting of 80 individuals?
3. A homozygous dominant individual (AA) is crossed with an individual that is heterozygous for the same trait (Aa). What are the possible genotypes of the offspring, and what percentage of the offspring is likely to show the dominant phenotype?
4. Critical Thinking Some animals, such as cows, normally produce only one offspring from each mating. If a cow showed a dominant phenotype, why would a typical testcross be a difficult way to determine the genotype of that animal?
STRUCTURES AND FUNCTIONS Write the possible genotypes of the offspring in the Punnett square below. Then answer the questions in the spaces provided.
A plant with the genotype WwRr is crossed with another plant with the same genotype.
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Modern Biology 47 Mendel’s Legacy