Just the Facts

Authors

• Donald Lee, University of Nebraska-LincolnFollow
• Patricia Hain, University of Nebraska-Lincoln

Document Type

Learning Object

Date of this Version

2001

Citation

Plant and Soil Sciences eLibrary (PASSeL) Lesson

Comments

Published 2001, Don Lee and Patricia Hain. Used by permission.

Development of this lesson was supported in part by Cooperative State Research, Education, & Extension Service, U.S. Dept. of Agriculture under Agreement Number 98-EATP-1-0403 administered by Cornell University and the American Distance Education Consortium (ADEC). Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the view of the U.S. Department of Agriculture.

Abstract

Description of the fundamental concepts of trait inheritance in sexually reproducing species.

Introduction

You have probably noticed that parents share many or most of their traits with their offspring. This observation came to the attention of humans long before scientific investigation developed. Human curiosity about the basis of trait inheritance is long standing, but most of what we know about genetics has emerged through research from the past 100 years. The fundamental concepts of trait inheritance in sexually reproducing species will be described in this lesson. The classical experimental approach that revealed these principles will be described in the following two lessons. For now, we will focus just on the facts of how variation is inherited.

Learning Objectives

1. Explain the role of gametes in sexual reproduction, including how meiosis produces haploid sex cells and how fertilization restores the diploid chromosome number in offspring.
2. Describe the relationship among DNA, genes, chromosomes, and traits, and explain how genes encode proteins that influence phenotype.
3. Differentiate between key genetic terms—including allele, genotype, phenotype, homozygous, heterozygous, dominant, recessive, segregation, and independent assortment—and apply them correctly in context.
4. Describe how dominance relationships (complete dominance and lack of dominance) influence phenotypic outcomes in successive generations of sexually reproducing organisms.

Modules:

1. Overview
2. Learning Objectives
3. Concept 1: Sexually reproducing organisms make sex cells or gametes
4. Concept 2: Genes are stable, passed on in sex cells and control traits
5. Concept 3: Genes are a part of the chromosome and are found in pairs in somatic cells
6. Concept 4: Genes can change on occasion and the alternative version or allele may control the trait
7. Concept 5: Individuals can be homozygous or heterozygous.
8. Concept 6: Gene pairs associate and then separate during gamete formation
9. Concept 7: Gametes combine at random to form the individuals in the next generation
10. Concept 8: One allele can be dominant over another or show a lack of dominance
11. Concept 9: The segregation of genes allows geneticists to make predictions
12. Concept 10: Segregation can be predicted based on independent assortment