Introduction to Genetics

1. Introduction to Genetics

2. He was known as the “FATHER OF GENETICS” • He discovered how traits were inherited Who was Gregor Mendel? HEREDITY – the passing of traits from parents to offspring

3. Genetics The study of heredity, how traits are passed from parent to offspring or x = or

4. Mendel did his study on pea plants • Pea plants have many traits (tall/short, purple flowers/white flowers) • Pea plants can beself-fertilized or cross-fertilized Mendel’s Peas

5. Mendel crossed (bred) tall pea plants with short pea plants. Predict what the offspring were like. Tall x Short ?

7. Mendel allowed the F1 plants to self-pollinate

9. True-Breeding - these plants always create plants that look like themselves • Hybrids – offspring of true-breeding plants • Tall x Short = Hybrid Types of Plants

10. Some traits are dominant over others. Tall x Short = all tall offspring (hybrids) *Tall is the dominant trait * Short is recessive Dominance

11. Mendel discovered that each trait is controlled by two factors (alleles) Genes – factors that determine your traits Genes and Alleles

13. GENOTYPE  -  what genes, letters, the organism has (TT, Tt, tt) PHENOTYPE   - what it looks like (tall or short)

14. There are three basic kinds of genes: • Dominant - A gene that is always expressed and hides others • Recessive - A gene that is only expressed when a dominant gene isn’t present • Codominant - Genes that work together to produce a third trait

15. Dominant and Recessive Genes • A dominant gene will always mask a recessive gene. • A “widows peak” is dominant, not • having a widows peak is recessive. • If one parent contributes a • gene for a widows peak, and • the other parent doesn’t, the • offspring will have a widows • peak. Widows Peak

16. Punnett Square - A tool we use for predicting the traits of an offspring • Letters are used as symbols to designate genes • Capital letters are used for dominant genes • Lower case letters are used for recessive genes • Genes always exist in pairs

17. A Widows Peak, dominant, would be symbolized with a capital “W”, while no widows peak, recessive, would be symbolized with a lower case “w”. Father - No Widows Peak - w Mother - Has a Widows Peak - W

18. All organisms have two copies of each gene, one contributed by the father, the other contributed by the mother. Homozygous - Two copies of the same gene Heterozygous - Two different genes

19. For the widows peak: WW - has a widows peak Homozygous dominant Ww - has a widows peak Heterozygous ww - no widows peak Homozygous recessive

20. Since Herman has no widows peak, he must be “ww”, since Lilly has a widows peak she could be either “WW” or “Ww” Definitely ww Homozygous recessive Either Ww Heterozygous or WW Homozygous dominant

21. We can use a “Punnet Square” to determine what pairs of genes Lilly has • A Punnet Square begins with a box 2 x 2 • One gene is called an “allele” • One parents pair is split into alleles on top, the other along the side • Each allele is crossed with the other allele to predict the traits of the offspring Assume Lilly is heterozygous Ww W w Assume Herman is homoozygous recessive ww w Ww ww w Ww ww

22. Notice that when Lilly is crossed with Herman, we would predict that half the offspring would be “Ww”, the other half would be “ww” Half “Ww”, Heterozygous, and will have a widows peak Half “ww”, Homozygous, and will not have a widows peak W w w Ww ww w Ww ww

23. Genetics Another possibility is that Lilly might be “WW”, homozygous dominant. Assume Lilly is homozygous dominant WW W W Assume Herman is homoozygous ww Notice that all the offspring are heterozygous and will have a widows peak w Ww Ww w Ww Ww

24. So which is true? Is Lilly homozygous dominant (WW) or is she heterozygous (Ww)? W w W W w Ww ww w Ww Ww w Ww ww w Ww Ww

25. If Lilly were heterozygous, then 1/2 of their offspring should have a widows peak, 1/2 shouldn’t If Lilly were homozygous, all of their children will have a widows peak W w W W w Ww ww w Ww Ww w Ww ww w Ww Ww

26. Recall that Herman and Lilly had another offspring, Marylin. She had no widows peak, therefore, Lilly must be heterozygous.

27. Hair color is a perfect example of a trait What color hair should their children have? Snow White has dark hair Prince Charming is blond

28. Hair color is different from widows peak, no color is truly dominant. • Brown and blond are the two, true traits • Homozygous conditions produce either brown or blond hair • Heterozygous conditions produce red hair

29. For Snow White to have brown hair she must be homozygous dominant, “BB”, a blond Prince Charming must be homozygous recessive, “bb”. B B b Bb Bb b Bb Bb

30. All the offspring from Prince Charming and Snow White will therefore be heterozygous, “Bb”, and since hair color is codominant….. all their children will have red hair. +

31. Let's review what you know about genetics......

32. Check for understanding 1.  A one-eyed purple people eater is crossed with a two eyed purple people eater.  All of their offspring have two eyes.   Which trait is dominant? 2.  If you use the letter E for this gene.   What is the genotype of the offspring?  Are these offspring the F1 or F2 generation? 4.  If you crossed the offspring with each other?  How many ofthe new offspring would you expect to have two eyes?

33. More checking 5.   The passing of traits from parents to offspring is known as  ________________ 6.  Who was the father of genetics?  ______ 7.  A single gene will code for a _______________, such as flower color. 8.  Every gene is made of two __________