Mendelian Genetics

1. Mendelian Genetics

2. What are some terms we must understand????? • Genetics – the study of heredity – how genes or traits are passed to generations • What are some examples of traits? • ______________ • ______________ • ______________ • Our genes code for these traits!!!!!

3. Terms Allele – a factor or gene One allele is from each parent.

4. Other terms • Phenotype – the physical appearance of a trait, what you actually see • Genotype – what your actual genes code for. It is the allele pair.

5. Gregor Mendel • Mendel is considered the father of Genetics. • An Austrian Monk • Used garden peas to study inheritance patterns

6. Mendel studied plants with different traits. One factor or trait he observed was tall plants and short plants. • He used pure (true breeding) plants. He crossed pollinated these plants. • He crossed true breeding tall plants (TT) with true breeding short (tt)plants. • Found that all plants in the F1 generation were tall. (Tt)

7. P (Parental) Generation F 1 (Filial ) Generation F 2 Generation

8. Then Mendel crossed the plants with the Tt genotype and it produced 75% short and 25% tall. From this he formed a law of dominance, because he knew that one allele was dominant over the other. In this case which is dominant, short or tall? Which is recessive?

9. Mendel’s Laws • 1st Law – Law of Dominance – Some alleles will be shown while some other alleles will not be shown. In other words some alleles are shown, will others are hidden. • The trait that is shown is considered dominant because it masked (dominated) over the other traits. • The trait that was hidden or masked is considered recessive.

10. Again allele are factors or genes. If TT was the genotype of a plant then one Tcame from one parent the other Tcame from the other parent. • Using a capital letter will always represent a dominant allele and a lower case letter will represent a recessive allele.

11. Homozygous Vs. Heterozygous • Homo- means same, Hetero – means different • Homozygous is two of the same allele • Heterozygous is two differentallele • What would be an example of Homozygous Dominant? ______ • Heterzygous Dominant? _____ ___ • Homozygous Recessive? ________

12. Mendel 2nd Law • 2nd Law – Law of Segregation – States that during meiosis two alleles will separate. • Recall Meiosis – you create gametes. Law of Segregation ensures that each gamete will have one allele from the allele pair. • The hapliodcell will combine with another hapliodcell to regain an allele pair

13. Mendel’s Third Law • Law of Independent Assortment – States that alleles distribute randomly or independently during meiosis. • YyRr – gametes __________ • ___________________________ • _____________________________ • _____________________________

14. Monohybrids • Monohybrids are used to view the outcomes in offspring examining only one trait • A punnett square is a visual aid that is used to view traits.

15. Punnett Square

16. Probability • The probabilityis the chance of a certain outcome. • Example: What is the chance of either having a girl or boy? • Each outcome will be independent of the other.

17. Ratios • Phenotypic Ratios - • Genotypic Ratios-

18. Dihybrids Looks at the possibilities of two Different traits.

19. More on Mendels Experiments • He also look at peas ___________ and __________ • Lets do a monohybrid cross look at color • Now lets look at color and shape

20. Now lets look at color and shape