Module 6 Mendelian Genetics

Introduction

You expect to look like your parents and your other ancestors, yet you are a little bit different. A monk in a garden discovered how species and individual traits are inherited. If it weren’t for Gregor Mendel and the garden pea, genetics might still be in the Dark Ages. Using this simple organism, Mendel developed evidence for the basic principles of genetics. In this Module, you will explore the concepts of dominance, segregation, and independent assortment. You will analyze ratios and probabilities of genotypes and phenotypes to examine many other possible ways of transmission of traits from generation to generation. You will discover how variability can be dependent on the number of genes involved in a trait, crossing over, and gene linkage. You will also learn why some traits like hemophilia are more common in males than in females. There are many tools that can be used to study the transmission of traits, and you will have the opportunity to use these tools in your study of some common heritable traits.

Think about the following question as you complete this module:

• What are the basic rules and steps involved that effect the transmission of genetic characteristics to the next generation?

• In This Module

• Lesson 1: Theories and Terminology of Inheritance

  In this lesson you will explore and become familiar with the language of genetics. You will be introduced to a nineteenth century monk, Gregory Mendel, and learn why he is considered the Father of Genetics.

  You will consider the following essential questions:

  • What is the basic language of genetics?
  • How does the work of Mendel explain the basics of Classical Genetics?

  Lesson 2: Mendel’s Laws and Monohybrid Crosses

  In this lesson, you will learn the patterns of inheritance that Mendel first discovered in pea plants. You will become familiar with techniques and conventions used by geneticists to trace the inheritance of traits from one generation to the next.

  You will consider the following essential questions:

  • What are the simple principles of single trait inheritance?
  • How can genotype be determined from phenotype?

• Lesson 3: Multiple Alleles and Incomplete Dominance Crosses

• In this lesson, you will explore traits that do not follow Mendel’s patterns of simple dominance, but can still be explained by his laws. You will understand how genes can have more than two alternate forms.

  You will consider the following essential questions:

  • What happens when one allele is not completely dominant over another?
  • How does having more than two alleles for a gene affect the possible phenotypes for a trait?

  Lesson 4: Dihybrid Crosses

  In this lesson, you will learn how to follow the inheritance of two separate traits at the same time. As you follow two traits at once, you understand how the movement of alleles for one trait, does not effect the other trait during the formation of gametes.

  You will consider the following essential questions:

  • How do scientists track the inheritance of more than one trait at a time?

  Lesson 5: Probability

  In this lesson, you will learn how to predict the genetic outcome of future generations by examining numbers and ratios. Patterns can give the likelihood of a trait remaining hidden or being expressed.

  You will consider the following essential questions:

  • How can ratios be used to analyze types of inheritance or to predict the possibility of a trait appearing in the next generation?

  Lesson 6: Chromosomal Theory and Sex-linked Inheritance

  In this lesson, you will begin to explore inheritance patterns that do not follow Mendel’s laws. You will see how some traits occur more frequently in one gender over another, and are said to be linked.

  You will consider the following essential questions:

  • Why do some traits appear more frequently in one gender than the other?
  • How did Thomas Hunt Morgan’s work provide experimental support for the chromosomal theory of inheritance?

  Lesson 7: Genes and the Environment

  In this lesson, you will examine the effect the environment may have on the expression of genes.

   

  You will consider the following essential questions:

  • How does the environment affect the expression of genes?

  Lesson 8: Polygenetic Traits

  In this lesson, you will study traits that are controlled by many genes. You will recognize inheritance patterns that have gradual changes in phenotypes, and you will understand that the expression of one gene can turn the expression of another on or off.

  You will consider the following essential questions:

  • How might multiple genes combine to form a single trait?

  Lesson 9: Crossing Over Frequencies and Gene Mapping

  In this lesson, you will learn how genes that are found on the same chromosome tend to move together, and are thus said to be linked. Using your understanding of crossing over from meiosis, you will learn how this allows scientists to map the relative location of genes that are found on the same chromosome.

  You will consider the following essential questions:

  • How does crossing-over in chromosomes relate to finding the position of genes?
  • What is the importance of knowing the location of specific genes on a chromosome?

  Lesson 10: Plant, Animal, and Human Genetics

  In this lesson, by learning to create and analyze pedigrees you will be able to track the inheritance of rare genetic diseases through families.

  You will consider the following essential questions:

  • What technologies exist to help us explain and predict the inheritance of traits in breeding programs and/or family histories?