1. Bell Question: Explain the difference between a phenotype and a genotype. The phenotype is what a trait looks like. The genotype is the specific alleles that code for the phenotype. Answer : Mendel and Genetics, Continued…

2. Last time we learned … Mendel and Genetics, Continued… … that Gregor Mendel is the Father of Genetics. … he looked at pea plants and studied various, discrete traits. … that there were ratios that seemed to consistently describe what happened in the plants. … how to use Punnett Squares to predict the ratios of phenotypes. … the difference between genotypes and phenotypes. … how different alleles affect the phenotype. We’re not done! Onward and upward!

3. Mendel and Genetics, Continued… We can continue to further describe genotypes. Dominant and recessive are helpful, but they help us more with phenotypes. For this, we say that GG is homozygous dominant. How could we describe gg?homozygous recessive GG and gg are homozygous. The alleles are the SAME. GG is for green, while gg is for yellow.

4. WordDefinitionPicture Homozygous having two of the same alleles for a gene GG gg Mendel and Genetics, Continued…

5. What about Gg? Its phenotype is for green peas. It has one allele for green peas and one allele for yellow peas. We call this genotype heterozygous. Heterozygous is one of each allele. We KNOW that one of the alleles is dominant, so the plant would grow green peas. Mendel and Genetics, Continued…

6. WordDefinitionPicture Heterozygous having two different alleles of a gene Gg Mendel and Genetics, Continued…

7. This is a German family tree from the 1500s. We can study the tree and learn about the relationships between members. We can also create a genetic tree to learn about the phenotypes and genotypes of families.

8. Mendel and Genetics, Continued… This special tree is called a pedigree. Looks a little different, doesn’t it? In a pedigree, we look at specific phenotypes which can lead to figuring out an individual’s genotype.

9. Mendel and Genetics, Continued… The circles are females. The squares are males. The red individuals are affected (have a specific phenotype). The blue individuals are not. Let’s take a closer look.

10. Mendel and Genetics, Continued… vertical lines mean offspring horizontal lines mean marriage Each row is a new generation second generation third generation first generation

11. Mendel and Genetics, Continued… If someone has the Ooga Booga disease, then he or she is considered affected (red). If you are in the third generation, who has Ooga Booga - your grandfather or your grandmother? your grandfather

12. Do you remember that when Mendel started his experiments, he began with mice but soon switched to pea plants? It was a great decision since pea plants reproduce quickly, have distinct traits, and the phenotypes are easily recognized. Mendel and Genetics, Continued…

13. Mendel and His Pea Plants Not all phenotypes are expressed so easily or clearly. Sometimes, it takes more than 2 alleles to express a trait. Sometimes, the phenotypes are a mixture. Sometimes, more than one trait is expressed. With Mendel, if the dominant allele was in the genotype, the dominant trait was the phenotype. Not so with these…

14. Mendel and Genetics, Continued… Some phenotypes are a blend of alleles. Camellia flowers are like this: R rr R Red flower White flower If you cross a red flower camellia with a white flower camellia, you get… PINK flowers! This is incomplete dominance.

15. WordDefinitionPicture Incomplete dominance offspring’s phenotype is a BLEND of the parents’ Mendel and Genetics, Continued… +

16. Codominance can also be expressed in offspring. Codominance is when the phenotypes of BOTH parents are seen in the offspring. When the red bull mates with the white cow, the offspring have BOTH red and white hair.

17. WordDefinitionPicture Codominance the phenotypes of BOTH parents are seen in the offspring Mendel and Genetics, Continued…

18. Sometimes there are more than two alleles. Blood types are like this. The three alleles to code for blood types are I A, I B, and i. I A and I B are codominant. What does that mean if a person is I A I B ? The person will show the phenotypes of BOTH alleles. I A and I B are both dominant over i. The i allele is recessive. The four blood types are A, B, O, and AB. The i allele is actually missing the markers that I A and I B have.

19. Mendel and Genetics, Continued… GenotypePhenotype Type A blood Type B blood Type O blood Type AB blood I A I A or I A i IAIBIAIB I B I B or I B i ii Can you figure out the phenotypes for these genotypes? Remember, I A and I B are codominant, and both these alleles are dominant to i.

20. Mendel and Genetics, Continued… Mendel thought that only one gene determines each trait. We now know that isn’t the case. Polygenic inheritance occurs when more than one gene determines the phenotype of a trait. Certain characteristics like height, eye color, and skin color are determined by more than one gene.

21. WordDefinitionPicture Polygenic inheritance when multiple genes determine a trait Mendel and Genetics, Continued… example: height

22. Mendel and Genetics, Continued… Genes are not the only thing that impact you. Your environment also affects your phenotype. Just because you may come from a long line of healthy hearts, doesn’t mean that you shouldn’t eat healthy foods and exercise. Your environment is an influence, too!

23. Mendel and Genetics, Continued… Exit question: When an offspring has a BLEND of its parents’ phenotypes, that is _______________ dominance.