Genetics & Gregor Mendel

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The story of Austrian monk Gregor Mendel discovering the foundations of genetics, as well as some basic terms. Tailored for 7th grade Science.

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Genetics & Gregor Mendel

  1. 1. Gregor Mendel (1822-1884) The Father of Genetics copyright cmassengale © Fall 2005, Pflugerville ISD, 7th Grade 1
  2. 2. 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 © Fall 2005, Pflugerville ISD, 7th Grade
  3. 3. 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 © Fall 2005, Pflugerville ISD, 7th Grade 3
  4. 4. Particulate Inheritance Mendel stated that physical traits are inherited as “particles” Mendel did not know that the “particles” were actually Chromosomes & DNA copyright cmassengale © Fall 2005, Pflugerville ISD, 7th Grade 4
  5. 5. Unit A : Chapter 1 : Section 1 © Fall 2005, Pflugerville ISD, 7th Grade
  6. 6. Mendel and His Peas • Mendel tested 7 traits: 1. 2. 3. 4. 5. 6. 7. Flower color Flower position Seed color Seed shape Pod shape Pod color Plant height p173 Life Science Textbook © Fall 2005, Pflugerville ISD, 7th Grade http://www.fieldmuseum.org/exhibits/traveling_mendel.htm
  7. 7. Mendel and His Peas • Mendel crossed flowers that were truebreeding 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 © Fall 2005, Pflugerville ISD, 7th Grade
  8. 8. Yes, copy the picture too.  • The first generation (F1) of plants all had purple flowers. (pp) Purple Parent (PP) © Fall 2005, Pflugerville ISD, 7th Grade White Parent (Pp) (Pp) • Where did the white color go?? (Pp) (Pp)
  9. 9. Mendel and His Peas • In the second generation (F2) he had 3 purple flowered plants, and 1 white flowered plant. Purple Parent (Pp) Purple Parent (Pp) • Mendel took two of his first generation (F1 x F1) purple flowered plants and crossed them together. (Pp) (Pp) © Fall 2005, Pflugerville ISD, 7th Grade (PP) (pp)
  10. 10. 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. © Fall 2005, Pflugerville ISD, 7th Grade
  11. 11. Mendel and His Peas • The color (purple) that seemed to mask over the recessive color was named the dominant trait. © Fall 2005, Pflugerville ISD, 7th Grade
  12. 12. 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. © Fall 2005, Pflugerville ISD, 7th Grade
  13. 13. 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 © Fall 2005, Pflugerville ISD, 7th Grade
  14. 14. 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. © Fall 2005, Pflugerville ISD, 7th Grade
  15. 15. 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 © Fall 2005, Pflugerville ISD, 7th Grade
  16. 16. 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. © Fall 2005, Pflugerville ISD, 7th Grade
  17. 17. 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. © Fall 2005, Pflugerville ISD, 7th Grade
  18. 18. 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? © Fall 2005, Pflugerville ISD, 7th Grade
  19. 19. Answer White Rabbit (bb) • The trait for black fur is dominant over the trait for white fur. The white fur trait is recessive. Black Rabbit (BB) (Bb) (Bb) (Bb) (Bb) http://www.buckeyevalleyfarms.freeservers.com/photo.html © Fall 2005, Pflugerville ISD, 7th Grade
  20. 20. Google’s tribute to Mendel July 2011 © Fall 2005, Pflugerville ISD, 7th Grade
  21. 21. Science Humor © Fall 2005, Pflugerville ISD, 7th Grade

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