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Visualizing Human Biology 5th Edition

Visualizing Human Biology (5th Edition)

Book Edition5th Edition
PublisherJohn Wiley & Sons
Section 21.1: Traits Are Inherited in Specific Patterns
Think Critically
Section 21.2: Modern Genetics Uncovers a Molecular Picture
Think Critically
Section 21.3: Genetic Theory Is Put to Practical Use
What a Scientist Sees
Section 21.5: Biotechnology Assists in Medical and Societal Issues
Ethics and Issues

Chapter 21, Section 21.1, Think Critically, Exercise 01

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There are certain traits in a pea plant that occur in pairs. These traits are never expressed in a blended manner. For example, the seed will either be round or wrinkled and not both. 

A cross between two plants, one having a round (Rr) seed, and another having a wrinkled (rr) seed will result into:


rRr (round)rr (wrinkled)
rRr (round)rr (wrinkled)


Since the allele for round seed is dominant over the wrinkled seed. Thus the genotype Rr produces round seeds. The cross produces 50% round seed and 50% wrinkled seed. Thus the traits appeared singly and never as a blend of two. The frequency of the traits occurring in the next generation was constant.

Verified Answer

  • M hypothesized that the proportion of traits occurring in the next generation was constant.
  • The hypothesis was tested by breeding a purple-flowered pea plant with a white flower pea plant. 
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