1. © Fall 2005, Pflugerville ISD, 7th Grade copyright cmassengale 1 Gregor Mendel (1822-1884) The Father of Genetics

2. © Fall 2005, Pflugerville ISD, 7th Grade Gregor Johann Mendel  Austrian monk  Studied the inheritance of traits in pea plants  Developed the laws of inheritance  Mendel's work was not recognized until the turn of the 20th century 2

3. © Fall 2005, Pflugerville ISD, 7th Grade Gregor Johann Mendel  Between 1856 and 1863, Mendel cultivated and tested thousands of pea plants  He found that the plants' offspring retained traits of the parents – this is now called “heredity” copyright cmassengale 3

4. © Fall 2005, Pflugerville ISD, 7th Grade copyright cmassengale 4  Mendel stated that physical traits are inherited as “particles”  Mendel did not know that the “particles” were actually Chromosomes & DNA Particulate Inheritance

5. © Fall 2005, Pflugerville ISD, 7th Grade Why peas, Pisum sativum?  Why Peas?  Produce lots of offspring  Grow quickly  Can be grown in a small area  Can be artificially cross- pollinated copyright cmassengale 5

6. © Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas Mendel tested 7 traits: 1.Flower color 2.Flower position 3.Seed color 4.Seed shape 5.Pod shape 6.Pod color 7.Plant height http://www.fieldmuseum.org/exhibits/traveling_mendel.htm p173 Life Science Textbook

7. © Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas Mendel crossed flowers that were true- breeding for each characteristic. He crossed a purple (PP) flowered plant with a white (pp) flowered plant. (Parent Generation) http://biology.kenyon.edu/courses/biol114/KH_lecture_images/Mendel/Mendel.html

8. © Fall 2005, Pflugerville ISD, 7th Grade Yes, copy the picture too. The first generation (F1) of plants all had purple flowers. Where did the white color go?? (Pp) (Pp) Purple Parent (PP) White Parent (pp)

9. © Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas Mendel took two of his first generation (F1 x F1) purple flowered plants and crossed them together. In the second generation (F2) he had 3 purple flowered plants, and 1 white flowered plant. (PP) (Pp) (pp) Purple Parent (Pp)

10. © Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas Mendel noticed in the first generation, all of the white flowers seemed to disappear. He called this a recessive trait. The white color faded into the background, and was not expressed physically. It showed up in the next generation when he pollinated the flowers.

11. © Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas The color (purple) that seemed to mask over the recessive color was named the dominant trait.

12. © Fall 2005, Pflugerville ISD, 7th Grade Mendel and His Peas Mendel found that each plant carried two sets of instructions for each characteristic (one from the “mom” and one from the “dad”). These sets of instructions are called alleles.

13. © Fall 2005, Pflugerville ISD, 7th Grade Vocabulary Heredity- the passing of traits from parent to offspring. Homozygous – both alleles are identical. Also known as True-breeding. Ex: PP or pp Heterozygous - each allele is different. Also known as hybrids. Ex: Pp

14. © Fall 2005, Pflugerville ISD, 7th Grade Vocabulary P generation- the parent generation. First-generation or F1- the very first set of offspring from two parents Second-generation or F2 – the offspring of the kids from the F1 generation (grandkids) Dominant trait- Represented with a capital letter, it overpowers the recessive trait.

15. © Fall 2005, Pflugerville ISD, 7th Grade Vocabulary Recessive trait- a trait that is apparent only when two recessive alleles for the same characteristic are inherited Genes- a segment of DNA that carries hereditary instructions and is passed from parent to offspring Alleles- multiple forms of the same gene

16. © Fall 2005, Pflugerville ISD, 7th Grade Vocabulary Genotype- the genetic code. Ex: Pp Phenotype- the physical appearance. Ex: Purple Flowers Pedigree – your family tree. Incomplete Dominance – a blend of the parents’ phenotypes. Ex: White flowering plant crossed with red flowering plant produces a pink flowering plant.

17. © Fall 2005, Pflugerville ISD, 7th Grade Vocabulary Codominance – When both phenotypes are visible. Ex: Hair that has both blond strands and brown strands. Karyotype – a chart of all your chromosomes lined up in order. Sex Chromosomes – chromosomes that determine a person’s gender. X-linked, or sex-linked inheritance – see p186 in Life Science Book.

18. © Fall 2005, Pflugerville ISD, 7th Grade Let’s Review 1. If you crossed a true-breeding black rabbit with a true-breeding white rabbit, all of the offspring would be black. Which trait is dominant in rabbits: black fur or white fur? 2. Which trait is recessive?

19. © Fall 2005, Pflugerville ISD, 7th Grade Answer The trait for black fur is dominant over the trait for white fur. The white fur trait is recessive. http://www.buckeyevalleyfarms.freeservers.com/photo.html (Bb) (Bb) (Bb) Black Rabbit (BB) White Rabbit (bb)

20. © Fall 2005, Pflugerville ISD, 7th Grade Google’s tribute to Mendel July 2011

21. © Fall 2005, Pflugerville ISD, 7th Grade Science Humor