1. Genetics: The Study of Heredity I.Review A.Why do you look like your parents? They gave you your DNA B.How is this information transferred? Through sexual reproduction (gametes and fertilization) C. What do we call a segment of DNA that codes for a protein? Gene D. Where are genes located? On chromosomes E. How many chromosomes do humans have? 46 (23 from Mom, 23 from Dad) F. How many genes are on human chromosomes? Estimated at about 20,000 - 25,000 genes in the human genome, containing 3 million base pairs

2. II.General Info A.Genetics is the study of heredity 1.Heredity – passing of traits from parent to offspring (baby) 2.Another word for “trait” is characteristic. A trait is something that can be scientifically observed, such as: What determines our traits? What determines our traits? Our genes!

3. Another genetic trait we can investigate is called hitchhikers thumb:

4. B.Gene - a segment of DNA that codes for a protein. It controls an organism’s form and function.

5.  Each gene can control one or more trait (ex. human eye color is controlled by at least 5 different genes!)  Human DNA is made of ~ 20,000 - 25,000 genes  A gene can have different forms or physical expressions of a trait known as an allele (ex. You have a gene for little finger type with two alleles: bent and straight)

6. C. Organisms get half of their genes from each parent when sperm and egg meet

7. Our genes influence how we look

8. And in many cases genes influence how we act

9. III. Gregor Mendel: “Father of Modern Genetics” (1824-1884) A.Mendel’s Life 1. Austrian monk born in current Czech Republic 2. Joined a monastery, then studied math and science at the U. of Vienna 3. As a monk he taught high school and cared for the monastery garden, which is where he developed his ideas on genetics 4. Significance of his work was not recognized until the early 1900’s

10. B.Mendel’s Experiment 1.He cross-bred pea plants with different characteristics, then studied 7 plant traits (seed/pea shape, color, height, etc.) of the hybrid offspring Seed Shape Flower Position Seed Coat Color Seed Color Pod Color Plant Height Pod Shape Round Wrinkled Round Yellow Green Gray White Smooth Constricted Green Yellow Axial Terminal Tall Short YellowGraySmoothGreenAxialTall

11. 2.All of the first generation offspring (F 1 ) had the characteristics of only one of the parent plants(P) DRAW THIS  Why did the “short” trait appear in the F 2 generation but not in the F 1 generation? P Generation F 1 Generation F 2 Generation TallShortTall Short

12. Although Mendel did most of his genetics work on pea plants, his ideas about genetics also apply to humans…

13. IV.Mendel’s Basic Principles of Genetics A.Every trait is determined by a pair of “units” B.Each parent provides one unit (allele) C.Each gene has forms called an allele. 1.If an organism has 2 of the same alleles for a trait, it is purebred. 2.If the organism has different alleles for a trait, it is hybrid 3.Example in pea plants: Height a.T = tall allele t = short allele b.Purebred plant is TT or tt c.Hybrid plant is Tt

14. D.Some alleles can cover-up the expression of the other a.Dominant allele always show b.Recessive allele is hidden when it is with a dominant allele

15. E.In the formation of sperm and eggs (gametes), one member of each allele separates into different gametes. This is called segregation F.How the alleles segregate during gamete formation is determined by chance. This is called Independent Assortment

16. V.Important Terms A.Genotypes are the letters used to describe the two alleles of a gene (ex. TT, Tt, tt) 1.Homozygous genotype means both alleles are the same (purebred) therefore we use the same letters a.Dominant alleles are represented by Capital letters (ex. a plant that has two dominant alleles is homozygous dominant = TT) b.Recessive alleles are represented by the same letter but lower case (ex. a plant that has two recessive alleles is homozygous recessive = tt) 2.Heterozygous genotype (hybrid) means one dominant and one recessive allele (ex. heterozygous = Tt)

17. B.Phenotype  The physical expression of the genotype (Ex. Eye, hair, skin color. Flower color, shape and location)

18.  Probability and Punnett Squares A. Genetics & Probability 1.Probability is the likelihood that a particular event will occur (e.g. coin toss) 2.Can be used to predict the outcomes of genetic crosses 3.Probability does not predict precise outcomes 4.The larger the number of events, the more accurate the probability 5.In genetics, the larger the number of offspring, the closer the resulting offspring will be to what was predicted

19. B. Punnett squares 1.Punnett square is a diagram used to determine the gene combinations that might result from a cross 2.Used to predict genetic variations that will result from a cross

20. Monohybrid Cross (cross for only one trait) Draw