11.1 The Work of Gregor Mendel

Understand Key Concepts

1. Different forms of a gene are called

   1. hybrids.

   2. dominant factors.

   3. alleles.

   4. recessive factors.

2. Organisms that have two identical alleles for a particular trait are said to be

   1. hybrid.

   2. heterozygous.

   3. homozygous.

   4. dominant.

3. Mendel had many stocks of pea plants that were true-breeding. What is meant by this term?

4. Explain how Mendel kept his pea plants from self-pollinating.

Think Critically

5. Design an Experiment In sheep, the allele for white wool (A) is dominant over the allele for black wool (a). A ram is a male sheep. How would you determine the genotype of a white ram?

6. Infer Suppose Mendel crossed two pea plants and got both tall and short offspring. What could have been the genotypes of the two original plants? What genotype could not have been present?

11.2 Applying Mendel's Principles

Understand Key Concepts

7. A Punnett square is used to determine the

   1. probable outcome of a cross.

   2. actual outcome of a cross.

   3. result of incomplete dominance.

   4. result of meiosis.

8. The physical characteristics of an organism are called its

   1. genetics.

   2. heredity.

   3. phenotype.

   4. genotype.

9. The probability of flipping a coin twice and getting two heads is

   1. 1.

   2. 1/2.

   3. 1/4.

   4. 3/4.

10. List the four basic principles of genetics that Mendel discovered in his experiments. Briefly describe each of these principles.

11. In pea plants, the allele for yellow seeds is dominant over the allele for green seeds. Predict the genotypic ratio of offspring produced by crossing two parents that are heterozygous for this trait. Draw a Punnett square to illustrate your prediction.

Think Critically

12. Apply Concepts In guinea pigs, the allele for a rough coat (R) is dominant over the allele for a smooth coat (r). A heterozygous guinea pig (Rr) and a homozygous recessive guinea pig (rr) have a total of nine offspring. The Punnett square for this cross shows a 50 percent chance that any particular offspring will have a smooth coat. Explain how all nine offspring can have smooth coats.

11.3 Other Patterns of Inheritance

Understand Key Concepts

13. A situation in which a gene has more than two alleles is known as

    1. complete dominance.

    2. codominance.

    3. polygenic dominance.

    4. multiple alleles.

14. A pink-flowered Mirabilis plant (RW) is crossed with a white-flowered Mirabilis (WW). What is the chance that a seed from this cross will produce a red-flowered plant?

    1. 0

    2. 1/4

    3. 1/2

    4. 1

15. What is the difference between multiple alleles and polygenic traits?

16. Why can multiple alleles result in many different phenotypes for a trait?

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