DSW

1. DSW True or False- Dominant traits are the most common traits in a population. Explain your answer

2. When people hear the word “dominant”, often they incorrectly believe that the majority of the population expresses this trait. Describing a trait as dominant does not mean it is the most common; it means that it is expressed over the recessive trait.  • How frequently a trait is observed in a population is not related to whether or not it is dominant or recessive. Instead, it is a reflection of how frequently the gene responsible for causing a trait is found in people. For example, polydactyl, the presence of extra fingers and/or toes, can be caused by a dominant mutation. However, polydactyl only occurs in 0.31-6.18 births in 1,000, depending on ethnic background. This means it is very rare for a person to have the gene mutation that causes polydactyl, even though it is dominant.

3. Beyond Dominant and Recessive • Not all genes show dominant and recessive alleles • Genetics is complicated- the majority of genes have more than two alleles • Many traits are controlled by more than one gene • Height- 7 to 20 genes • Skin color- 100 genes • Eye color- 8 genes • Not a distinct class but a wide range Some alleles are neither dominant or recessive, many traits are controlled by multiple alleles or multiple genes

4. Incomplete Dominance • One allele is not completely dominant over another • The heterozygous phenotype is somewhere in between the two homozygous phenotypes

5. Codominance • Both alleles contribute to the phenotype of the organism

7. Wrap-up • 1 minute power write • Share with someone NOT sitting by you • Student developed test questions • To deepen your understanding, develop test questions that identify the most important concepts • Prepare and answer 3 of your own test questions- turn in to me  • Practice- Codominance and Incomplete dominance