Are you Unique?

1. Are you Unique? • Dimples? • Able to roll your tongue or not? • Curly or straight hair?

2. Are You Unique? • Widow’s Peak or not? • Free or attached lobes?

3. Traits • Individuals have many characteristics or traits that make each of us unique. • Trait = specific characteristic that varies from one individual to another

4. Genetics – The Study of Heredity • Interest in the passing of traits from one generation to the next is not new • Agriculture was developed around 12,000 years ago. People selected the plants and animals with the best traits to raise. • Example: Farmers selected wild grass plants with the largest seeds to produce corn

5. Gregor Mendel – Father of Genetics • Born in 1822 in what is today the Czech Republic. • At university he studied for the priesthood, as well as, math and science. • He wanted to become a teacher, but he had TERRIBLE test taking anxiety—and was unable to pass the teacher’s exam.

6. Gregor Mendel – Father of Genetics • Mendel became a monk • He taught high school (part-time) and worked in the monastery garden. • Between 1856-1868, Mendel conducted experiments on inheritance with the common garden pea. .

7. Pea Plants

8. Mendel’s Genetic Work • Mendel experimented with 7 different traits of peas.

9. Reproduce sexually Large number of offspring (peas on a pod) easily produced Genetic crosses are easily controlled What made the Pea a Good Organism to Work with?

10. Peas are True Breeding plants (=the parent plant normally produces offspring identical to itself), because they self-pollinate. Mendelian Genetics

11. Mendelian Genetics Tall plant x Tall plant All Tall plants • Mendel studied each of the 7 different traits one at a time • He began his work by breeding together two True Breeding plants. • A True Breeding plant self-pollinates and always has offspring that share its traits. • Example: Tall plants always produce tall plants. Short plants always produce short plants. Short plant x Short plant All Short plants

12. Mendel’s Experiments • Mendel asked, “What happens if I cross a true breeding tall plant with a true breeding short plant?”

13. Mendel’s Experiment • Mendel asked, “What happens if I cross a true breeding tall plant with a true breeding short plant?” • The plants produced seeds. • The seeds were planted • Every seed produced a TALL plant F1 generation P generation

14. Mendel’s Results • Mendel’s First Conclusion: biological inheritance is determined by factors that are passed form one generation to the next. • Today we know these factors as genes.

15. Mendel’s Second Experiment • Mendel crossed plants from the F1 generation together. • He created thousands of crosses this way. • Each flower produced seeds. • Thousands of these seeds were planted and grew into the F2 generation.

16. Mendel’s Results of the F1 Cross • Mendel observed the thousands of plants he grew from seeds. • He found the missing trait had reappeared!! • Among the new F2 generation there was a 3:1 ratio of Tall to Short Plants P generation F1 generation F2 Generation

17. Mendel’s Second Conclusion • Second Conclusion: Principle of dominance – Some alleles are dominant and some are recessive. An organism with one or two dominant alleles for a particular form of a trait will always have that form. ********************** • An organism inherits TWO alleles for every trait. One from its mother and one from its father.

18. Vocabulary • Gene – • Allele – • Dominant - • Recessive - • Hybrid = • Pure = • True breeding =

19. Vocabulary • Gene - unit of heredity information • Allele – form of a gene (Tall/Short). • Dominant - stronger of two alleles • Recessive - weaker of two alleles • Hybrid = offspring of parents with different traits. A hybrid has one recessive gene and one dominant gene • Pure = both genes are the same (2 recessive or 2 dominant) = homozygous • True breeding = P generation = pure

20. Rules for Genetic Problems • Two alleles for a gene are represented with the same letter. • Dominant alleles are represented with an uppercase letter, and recessive alleles are represented with a lower case letter. • The letter representing the gene is usually the first letter of the dominant trait. • For example: Tall allele = T; Short allele = t

21. Rules for Genetic Problems • Try this: • A pea plant has two alleles for seed color. • Yellow is the dominant seed color • Green is the recessive seed color. • What is the symbol for yellow seed color?_____________ • What is the symbol for green seed color? _____________ Y y

22. Rules for Genetic Problems • Since a plant inherits two alleles for seed color it may be • YY = yellow seeded plant • Yy = yellow seeded plant • yy = green seeded plant. 

23. More Vocabulary • Homozygous genes = same alleles for the trait (YY, yy) = pure • Heterozygous genes = different alleles for the trait (Yy) = hybrid • Genotype = genetic make-up of an organism. • Phenotype = physical characteristic of an organism.

24. Punnett Squares • Named after R.C. Punnett, British geneticist, 1875-1967 • Used to understand the probability of the outcome of a genetic cross.

25. Punnett Square F1 generation cross

26. Practice • Cross 1 - Make a Punnett Square of a cross between the P generation of a yellow seeded plant (YY) and the F1 generation (Yy) • Cross 2 - Make a Punnett Square of a cross between the P generation of a green seeded plant (yy) and the F1 generation (Yy) • What is the phenotype and genotype for the offspring in cross 1? Cross 2?