Outcomes:  Students will be expected to:

  • demonstrate an understanding of Mendelian genetics (315-3)
    • explain the meaning of the Incomplete dominanc
  • interpret patterns and trends in genetic data (214-5)
  • state a prediction and a hypothesis based on available genetic evidence using genetic problems (212-4)
    • predict the outcome of monohybrid and dihybrid crosses for incomplete dominance

Introduction

text versionWhen you were first introduced to the topics of genetics and Mendel’s pea plant experiments, you might have been asked about the F1 generation of his peas with the example of height. What would the offspring have been like in a cross between a tall pea plant and a short pea plant? Earlier on you might have thought that the answer would have been medium height. Of course we now know that tall plants are dominant to short plants which are recessive.

Is this a case for all characteristics of all organisms! In fact, no, you are going to learn in this lesson that there are some instances in plants and animals when a dominant and a recessive are brought together in a heterozygous condition, there is a blending of the two-traits, this is called Incomplete Dominance. In the Introductory page, you will notice that for color in flowers, red and white do sometimes make pink and there are a number of ways that can be written. Pay attention to that because all of those may show up on a public exam.

There are a number of different methods to represent the alleles for incomplete dominance. For example, in incomplete dominance for flower colour in snapdragons the following can be used:

(i) R - red R’ - white

(ii) FR - red Fw - white

(iii) R - red W - white

References

Text Reference: 

Read the following reference page in the McGraw-Hill text: 541

Prerequisites

  • There is no prerequisite knowledge for this lesson.