Corn Genetic assignment

GENETIC INHERITANCE PROBLEMS

OBJECTIVES

Note:

A lleles

locus

P 1 generation

F 1 g eneration

Note:

Genetics Inheritance Problems

Instructions: Work in lab groups to count kernels and solve the genetics problems. Materials: Genetic corn cobs with kernels, calculator

1. CROSS # 1: corn kernels (seeds)

purple

yellow

F1 p lants that all had purple corn kernels

Po generation:

Genotype F1

The F1 corn plants with the purple corn kernels were interbred

2

F1 cross:

F2 generation:

e xpected F2

expected percentage

P rocedure: The F2 c ontainer in the lab labeled F2 of

C ross 1 observed

TABLE 1: Phenotypes of Corn Kernels for F2 Generation of Cross 1 (observed data)

6

4

2

2

TABLE 2: Observed and expected data for F2 generation of Cross 1

2

2. CROSS # 2: F1 purple corn kernels with yellow corn kernels.

F

F1

F2 generation:

e xpected F2

expected percentage

Procedure: of cross 2.

observed

TABLE 3: Phenotypes of Corn Kernels for F2 Generation of Cross 2 (observed data)

6

4

2

observed expected.

TABLE 4: Observed and expected data for F2 generation of Cross 2

3. CROSS # 3: purple, wrinkled seeds

(kernels) yellow, smooth seeds (kernels)

purple and smooth.

Write in the parents genotypes (Po generation) and the genotype of their

Po generation:

F1 generation:

2

F1 cross:

F2 generation:

e xpected F2

P rocedure: The F2 c ontainer in the lab labeled F2 of

C ross 3. t en observed

TABLE 5: Phenotypes of Corn Kernels for F2 Generation of Cross 3 (observed data)

TABLE 6: Number observed and expected data for F2 generation of Cross 3

TABLE 7: Percent observed and expected data for F2 generation of Cross 3

P ×

P ×

F

Lab Exercise 12

If two wavy-haired parents had twelve children, how many of their offspring would be expected to be curly? Wavy? Straight?

5. A woman with normal vision, whose father was color-blind, married a man who had normal vision. The genes for normal vision and color-blind vision are on the X chromosome. The color­

blind characteristic is recessive. What are the expected F1 genotypes and F1 phenotypic ratio from this mating?

P1 cross:

Gametes: Punnett Square:

F1 genotypes:

F1 phenotypic ratio:

Questions:

1. State Mendel's First Law. What part of meiosis is the basis for this law?

2. State Mendel's Second Law. What part of the meiotic process is the basis for this law?

287

Lab Exercise 12

3. Why do we use Punnett squares to solve genetics problems?

4. All of the genetics problems in this lab exercise involved monogenic traits. In reality however, most genetic traits are polygenic. Compare monogenic traits with polygenic traits. Which traits are easier to predict outcomes from matings?

5. (OPTIONAL) If genetic engineering (gene technology) is ever successful in curing people of a genetic disease, would the disease more likely be monogenic or polygenic? Why?

288