1. The Work of Gregor Mendel

2. Question Have you ever wondered why everyone in your family is tall, but you are short? Have you ever wondered why everyone in your family is tall, but you are short? Have you ever wondered why brothers and sisters can look different, or look so much alike? Have you ever wondered why brothers and sisters can look different, or look so much alike?

3. Mendel Called the “Father of Genetics” Called the “Father of Genetics” Studied patterns of heredity of pea plants. Studied patterns of heredity of pea plants. Genetics – the study of heredity Genetics – the study of heredity

4. Three Conclusions to His Research Principle of Dominance and Recessiveness One allele in a pair may mask the effect of the other Principle of Segregation The two alleles for a characteristic separate during the formation of eggs and sperm Principle of Independent Assortment The alleles for different characteristics are distributed to reproductive cells independently.

5. Mendelian genetics Character (heritable feature, i.e., fur color) Character (heritable feature, i.e., fur color) Trait (variant for a character, i.e., brown) Trait (variant for a character, i.e., brown) True-bred (all offspring of same variety) True-bred (all offspring of same variety) Hybridization Hybridization (crossing of 2 different true-breds) P generation (parents) P generation (parents) F 1 generation (first filial generation) F 1 generation (first filial generation)

6. Genetic vocabulary……. Punnett square: Punnett square: Gene: point on a chromosome that controls the trait Gene: point on a chromosome that controls the trait Allele: an alternate form of a gene A or a Allele: an alternate form of a gene A or a Homozygous: identical alleles for a character Homozygous: identical alleles for a character Heterozygous: different alleles for a gene Heterozygous: different alleles for a gene Phenotype: physical traits Phenotype: physical traits Genotype: genetic makeup Genotype: genetic makeup Testcross: breeding of a recessive homozygote X dominate phenotype (but unknown genotype) Testcross: breeding of a recessive homozygote X dominate phenotype (but unknown genotype)

7. How can the Chances of an Offspring’s Traits be Determined? BY USING A PUNNETT SQUARE BY USING A PUNNETT SQUARE Get out your Punnett Squares Problems Get out your Punnett Squares Problems

8. Bb X Bb Phenotypic Ratio 3:1 Genotypic Ratio 1:2:1 B b B b B B B b b B b b

9. What about two traits? What about two traits? Complete the second half of your Punnett Square Problems Complete the second half of your Punnett Square Problems Dihybrid Cross

10. BbTt x BbTt BTBtbTbt BT BBTTBBTTBBTTBBTTBBTtBbTTBbTt BtBBTtBBttBbTtBbtt bTBbTTBbTt bbTTbbTTbbTTbbTTbbTt btBbTtBbttbbTtbbtt

11. Exceptions to Mendel’s Rule

12. Incomplete Dominance The phenotype of the heterozygote is intermediate between those of the two homozygotes. The phenotype of the heterozygote is intermediate between those of the two homozygotes. Ex) Snap Dragon Color Ex) Snap Dragon Color Red, Pink, White Red, Pink, White

13. Co-dominance Phenotype of both homozygotes are produced in heterozygotes individuals. Phenotype of both homozygotes are produced in heterozygotes individuals. Both alleles are expressed equally. Both alleles are expressed equally. Ex)Roan Cattle Ex)Roan Cattle White-feathered birds are both homozygotes for both B and W alleles

14. Multiple Alleles Ex )Blood type Ex )Blood type Blood type A and B are co-dominant, while O is recessive. Blood type A and B are co-dominant, while O is recessive. Forms possible blood types of A, B, AB, and O. Forms possible blood types of A, B, AB, and O.

15. Blood Also Shows Codominance

16. Sex-Determination Chromosome pairs 1-22 are autosomes Chromosome pairs 1-22 are autosomes Chromosome pair 23 are sex chromosomes Chromosome pair 23 are sex chromosomes They determine the sex of an individual They determine the sex of an individual XX = femaleXY = male XX = femaleXY = male

17. Sex-Linked Inheritance Traits that are only found on the X chromosome Traits that are only found on the X chromosome Colorblindness and Hemophilia are examples of sex-linked traits. Colorblindness and Hemophilia are examples of sex-linked traits. These genes are recessive and found only on the X chromosome. These genes are recessive and found only on the X chromosome.

18. Polygenic Inheritance Inheritance pattern of a trait that is controlled by two or more genes. Inheritance pattern of a trait that is controlled by two or more genes. Gene may be on the same chromosome or on different chromosomes. Gene may be on the same chromosome or on different chromosomes. Ex) Skin color and Height Ex) Skin color and Height