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In this chapter

(^1818)

The Basis of Heredity

chapter

The Basis of Heredity

Exploration: Similarities

and Differences

Mini Investigation:

Cross-Pollination

Web Activity: Creating a

Personal Profile

Explore an Issue: Genetic

Screening

Web Activity: Pedigree

Analysis

Investigation 18.1: How

Do Environmental Factors

Affect Gene Expression?

Case Study: A Mystery of

Blood Types

Investigation 18.2:

Genetics of Corn

Explore an Issue:

Drought-Tolerant and

Salt-Tolerant Plants

Have you ever been able to identify a person as a member of a particular family by cer-

tain physical traits? Some traits, such as curly hair or a prominent nose, can be traced

through a family’s lineage. Heredity is the transmission of biological traits from par-

ents to offspring. When the members of different generations all share a particular trait,

this is evidence that the trait is inherited. Genetics is the study of inheritance of biolog-

ical traits.

Biological traits are determined by genes, which are specific segments of DNA. During

reproduction, genes of the parent or parents are transmitted to the next generation.

Long before we knew of genes and DNA, humans were able to use knowledge of trans-

mission of biological traits to their advantage. Domesticated animals, such as cows and

dogs, were produced by choosing parents having traits that were desired in the offspring.

Crop plants were also developed by selecting parents with desirable traits.

Every person inherits one of about eight million possible combinations of his or her

parents’ chromosomes. Your set of genes and your traits are therefore all your own. Even

twins who are genetically identical may not share all the same traits.

What patterns can be found in the transmission of genetic traits? How do these relate

to the transmission of genes? In this chapter, you will explore patterns of inheritance of

biological traits and explain how these patterns arise.

596 Chapter 18 NEL

Answer these questions as best you can with your current knowledge. Then, using

the concepts and skills you have learned, you will revise your answers at the end of

the chapter.

1. Is it possible for two parents with black hair to have a child with red hair?
   Why or why not?
   2.Sometimes, when breeders cross two individuals with valuable traits, the offspring
   do not show the same traits. Suggest a reason why this may be so.
   3.A team of researchers at the University of Alberta studied sets of identical twins to
   see if driving a truck or other heavy machinery was related to back pain. Each set of
   twins included one individual who drove for a living and another who did not. They
   found that the amount of back pain experienced by a truck-driving twin was the
   same as for the non-driving twin.
   (a) Why was it important to study identical twins?
   (b) Could the study have used fraternal twins instead? Why or why not?

STARTING Points

Career Connections:

Veterinarian; Agrologist