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Introductions to Genetics

Explore the basics of genetics and Mendel's experiments with pea plants. Learn about traits, alleles, and dominant vs. recessive genes.

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Introductions to Genetics

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  1. Introductions to Genetics Mendel and all that…

  2. Questions for you In your notes, answer these ?s: • Who in your family do you most look like? • In what ways do you NOT looklike that person? • Who in your family has interestsand preferences most like yours?

  3. Who Is This??

  4. Mrs. Hunter’s relative…. Which relative?

  5. Yep, you guessed it… It’s Mrs. Hunter’s……. Grandmother!

  6. I. Some terms A. Genetics = study of heredity B. Heredity= passing traits to offspring

  7. C. Traits 1. = characteristics that parents can pass to offspring 2. Examples of traits: Eye color Hair color Shape of eyebrows

  8. What traits do you share? 3. What traits do share with your parents? siblings? cousins?

  9. II. Gregor Mendel(1822-1884) A. Who was he? • Austrian monk • Studied the traits of pea plants • “Father” of modern genetics http://www.scienceshorts.com/gmendel.htm

  10. B. Mendel’s Work1. Background a. In peas, ♂&♀parts are in every flower b. Pollen = plant sperm c. Self-pollination= flower fertilizes itself d. Cross-pollination= flower fertilized by another flower http://www.sciam.com/article.cfm?articleID=F4604E0F-E7F2-99DF-30C88C9489BD83A2

  11. 1. Background e. Peas have a lot of traits f. Can’t study them all at once g. Mendel studied one at a time http://fig.cox.miami.edu/~cmallery/150/mendel/heredity.htm

  12. 2. Mendel’s Experiments a. Mendel controlled the pea pollination b. ¿ How did he do this?

  13. 2. Mendel’s Experiments • Removed ♂parts from a flower • Dusted ♀parts with pollen from another flower • ¿Was this self-pollination or cross-pollination? • cross-pollination

  14. 2. Mendel’s Experiments c. First Mendel crossed: purebred purebred white flowered plant x purple flowered plant (P1 generation) (P1 generation) all offspring were purple (F1 generation)

  15. 2. Mendel’s Experiments d. Then, he crossed the F1 generation with itself (self-cross) F1 X F1 3 offspring werepurple 1 was white (F2 generation)

  16. 2. Mendel’s Experiments e. What happened? • Did the traits blend? • Why were all the F1 flowers purple? • Why did we get 3 purple & 1 white in F2? http://www.biology.iupui.edu/biocourses/N100/images/headernotes.gif

  17. 2. Mendel’s Experiments f. Vocabulary we need: • Gene = part of a chromosome that codes for a trait or a protein (we have two genes for every trait) • Allele = a form of a gene E.g. white or purple flowers http://www.healthsystem.virginia.edu/internet/huntdisease/geninfo.cfm http://www.csulb.edu/~kmacd/361-6-Ch2.htm

  18. Vocabulary • Dominant = if present, is always expressed • Recessive = both recessive alleles must be present for expression

  19. Let B = purple Let b = white P1 x P1 F1 g. Back to Mendel P1 BB bb Bb http://www.biology.iupui.edu/biocourses/N100/2k4ch10genetics.html

  20. g. Back to Mendel F1 x F1 (self-cross) Bb x Bb 1 BB (purple) 2 Bb (purple) 1 bb (white) 3 purple 1 white http://uz.wikipedia.org/wiki/Genetika

  21. Questions • Which allele is dominant? Purple flowers or white flowers? • Did the alleles blend? NO, flowers were either white or purple, but not in between • Why were all the F1 flowers purple? purple is dominant • Why did we get 3 purple & 1 white in F2? purple is dominant

  22. More Vocabulary • Homozygous = 2 of SAME alleles for the same trait (BB or bb) • Heterozygous = 2 different alleles for the same trait (Bb)

  23. Practice • Copy the table in the Quick Lab on page 166 of the textbook into your notes • Circle your phenotype (physical appearance) for each trait • Count the # in class with each trait • Write the numbers in the boxes

  24. Questions • How many cleft chins: no clefts? • How many dimples: no dimples • How many hair above knuckles : hairless fingers? • How many freckles: no freckles? • For which phenotypes do we know the genotype (which genes are present)?

  25. Bibliography Graphics • Mendel picture http://www.scienceshorts.com/gmendel.htm 11/3/07 • Garden pea picture http://www.sciam.com/article.cfm?articleID=F4604E0F-E7F2-99DF-30C88C9489BD83A2 11/3/07 • Pea characters http://fig.cox.miami.edu/~cmallery/150/mendel/heredity.htm 11/3/07 • F1 cross http://www.biology.iupui.edu/biocourses/N100/2k4ch10genetics.html 11/3/07 • Punnett Square http://uz.wikipedia.org/wiki/Genetika 11/3/07 • Alleles http://www.csulb.edu/~kmacd/361-6-Ch2.htm 11/4/07 • DNA, genes, chromosomes http://www.healthsystem.virginia.edu/internet/huntdisease/geninfo.cfm 11/4/07

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