Lack of Dominance

Lack of Dominance

Objectives:

After completing this section, you should:

1. Define lack of dominance

2. Contrast complete dominance with a lack of dominance

3. Recognize where the results from monohybrid crosses or pedigrees can be

explained by the concept that alleles controlling a trait show a lack of dominance

4. Predict the outcomes from crosses in families where the trait of interest is

controlled by alleles that have a lack of dominance

5. Apply the concepts of dominance and lack of dominance to explain how genes

control phenotypes at the molecular level.

6. Predict what happens to phenotype and genotype variation when there is a lack of dominance and multiple alleles controlling a trait in a family.

Some key terms:

Complete dominance

Lack of dominance

Incomplete dominance

Co-dominance

Over dominance

Multiple alleles

Pleiotropy

On line lessons: none

Gene____: Controls which proteins are made and placed on the red blood cell surface

Allele: Different versions of this gene

A allele: ______B allele: ______O allele: ______

Phenotype: Type A is the genotype IA IA IA IO

Type B is the genotype IB IB IB IO

Type AB is the genotype IA IB

Type O is IO IO

Apply the term dominant allele to the above Apply the term lack of dominance to the above

Weed Genetics Example

Shattercane Story: Shattercane could be killed by a number of herbicides called ALS enzyme inhibitors

After a few years, many shattercane plants in farmers’ fields could resist the application of these ALS inhibitor herbicides.

Scientists at UNL collected the shattercane plants and did genetic studies.

ALS susceptible X ALS resistant (true breeding lines)

F1: All the F1s sprayed with the ALS inhibitor herbicide were hurt by the herbicide but did not die.

Explanation?

Experiment you would do to test your explanation?

Expected results