Biology Now, 2e

Dog Days of Science ■ 121

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When the planted seeds

grew into plants (F 1 ), he

allowed the plants to

self-fertilize, and once

again he harvested and

planted the seeds.

He harvested the seeds

from these matings and

planted them.

Mendel used a

paintbrush-like

instrument to

cross-fertilize

pea plants that

bred true for

flower color.

P generation

F 1 generation

F 2 generation

(^4) When these seeds grew into plants (F 2 ),
he observed and recorded the color of
their flowers—the trait of interest.
(^6) He repeated the experiment
for thousands of plants.
(^5) He analyzed his data using
statistics.

3

2

1

Figure 7.4

Mendel’s careful experiments

Mendel was meticulous in conducting his research and making observations, following a very careful protocol. Controlled breeding is

possible in flowering plants because they have both male and female reproductive structures. Mendel manipulated his P-generation

plants by removing all the female structures from one plant and all the male structures from the other, thus preventing self-

fertilization. He could then perform the initial cross by transferring pollen from the “male” plant to the flower of the “female” plant. M

Q1: What would you predict about the color of the F 1 plants’ flowers?

Q2: Why was it important that Mendel begin with pea plants that he knew bred true for flower color? Why couldn’t he

simply cross a purple-flowered plant and a white-flowered plant?

Q3: Over the years, Mendel experimented with more than 30,000 pea plants. Why did Mendel collect data on so many

plants? Why didn’t he study just one cross? Hint: Read “What Are the Odds?” on page 124 before answering.