Chapter 6

Genetics

6.1 Lesson 6.1: Gregor Mendel and the Foundations of Genetics

Lesson Objectives

• Explain Mendel’s law of segregation.


• Draw a Punnett square to make predictions about the traits of the offspring of a simple
  genetic cross.

Check Your Understanding

• What is the genetic material of our cells?


• How does meiosis affect the chromosome number in gametes?

Introduction

For centuries people have been fascinated with the inheritance of human traits. People
might say, “You have your father’s eyes.” or, “You have red hair like your granddad; it must
have skipped a generation.” These comments show an appreciation of the laws of human
inheritance. We inherit traits from our ancestors, and sometimes traits can stay hidden
and show up in later generations. Genetics,the study of inheritance, explains how traits
are passed on from one generation to the next. Due to recent developments in the field of
genetics, we can now seek to understand the inheritance of disease. People today may ask
“What are the chances my child will have cystic fibrosis?” and “What is the likelihood that I
may have breast cancer if my grandmother had it?” Genetic counselors are trained to address