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Genetics

Genetics . BY: BRIANNA SHIELDS. DO NOW. 1. How are the chromosomes organized in a cell undergoing the metaphase stage of mitosis? 2. What is the name of the process that creates body cells?

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Genetics

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  1. Genetics BY: BRIANNA SHIELDS

  2. DO NOW • 1. How are the chromosomes organized in a cell undergoing the metaphase stage of mitosis? • 2. What is the name of the process that creates body cells? • 3. If an organism has 30 chromosomes in each of its body cells, how many chromosomes must its sex cells contain?

  3. GOAL • To recognize differences between genes, DNA and chromosomes • To use a punnett square to predict the traits of offspring

  4. What Makes You, You • After watching the web interactive, “What Makes You, You?”, create a drawing relating the following terms: • Cell • Nucleus • Genes • DNA • Chromosomes • Sister Chromatids • Centromere • Allele

  5. Finding DNA Where is DNA found? 1. Tiny rod-like chromosomes are housed in the cell’s nucleus

  6. DNA- What is it? Where is DNA found? 2. Chromosomes are found in butterfly-shaped pairs (sister chromatid) Connected by a centromere

  7. DNA- What is it? Where is DNA found? 3. Inside each chromosomes is a coil of DNA

  8. DNA- What is it? Where is DNA found? 4. DNA is a double helix Ladder-like with rungs called bases

  9. DNA- What is it? Where is DNA found? 5. Several bases in DNA make-up a gene DNA is a long string of genes

  10. DNA- What is it? Where is DNA found? 6. Genes determine an individual’s inherited traits

  11. DNA-Chromosomes-Genes

  12. DNA-Chromosomes-Genes

  13. Human Karyotype

  14. Mendel’s Study of Genetics Gregor Mendel Father of Genetics (heredity) Crossed pea plants, counted offspring

  15. Mendel’s Study of Genetics Gregor Mendel Knew pea plants could self pollinate Forced pollination: Removed stamens from one plant Used brush to dust pistil with pollen from another plant

  16. Traits of Pea Plants

  17. History of Genetics Mendel’s Work He crossed tall ones and short ones to see what type of offspring they would have X

  18. History of Genetics Mendel’s Work He crossed tall ones and other tall ones Some short offspring, others tall Tall plants are not true breeders X

  19. History of Genetics Mendel’s Work Short plants x short plants = short offspring Short plants = true breeders X

  20. History of Genetics Mendel’s Findings Offspring produced had to do with the genes involved Inherit 2 genes for each trait- one from each parent 2 for eye color 2 for hair color 2 for widow’s peak 2 for tongue rolling 2 for ear shape

  21. Genetics Rules Rules of genetics 1. Genes are inherited in pairs 2. Dominant genes- expressed trait (capital letter) 3. Recessive genes- unexpressed trait (lowercase letter) 4. WHENEVER PRESENT, DOMINANT GENES HIDE/MASK RECESSIVE GENES

  22. Genetics Rules Example T= tall t = short TT = tall Tt = tall tt = short

  23. Genetics Rules Example G= green g= yellow GG = green Gg= green gg= yellow

  24. Genetics Rules Genotypes What are the possible gene combinations? TT = homozygous dominant True breeder tt= homozygous recessive True breeder Tt= heterozygous Hybrid

  25. Genetics Rules Genotypes Examples Bb Heterozygous rr Homozygous recessive LL Homozygous dominant mm Homozygous recessive Pp Heterozygous

  26. Genetics Rules Phenotypes What possible gene combinations will look like Ex: TT = tall

  27. Genetics Rules Punnett Squares Used to figure out the probability of having offspring with certain gene combinations

  28. G = Clear Skin g= Freckles

  29. Genetics Rules Creating Punnett Squares 1. Set up boxes 2. Create dominant and recessive key 3. Write out the cross 4. Add parent labels to punnett 5. Perform cross (2 genes per box) 6. Record genotype percentages Ex: 100% TT (Homozygous dominant) 7. Record phenotype percentages Ex: 100 % Tall

  30. Punnett Example: TT x Tt T T Genotypes: 50% TT Homozygous Dominant 50% Tt Heterozygous TT TT T Tt Tt t Phenotypes 100% Tall T= Tall t=Short

  31. Punnett Example: Tt x tt T t Genotypes: 50% tt Homozygous recessive 50% Tt Heterozygous Tt tt t Tt tt t Phenotypes 50% Short 50% Tall T= Tall t=Short

  32. Example • Brown eyes is dominant. Blue eyes is recessive. Cross a homozygous dominant and a homozygous recessive. • What percentages of blue-eyed and brown eyed offspring will you get?

  33. Punnett Example: BB x bb B B Genotypes: 100 % Heterozygous Bb Bb b Bb Bb b Phenotypes 100% Brown Eyed B= Brown b=Blue

  34. Example • A couple is hoping their child will have the tongue rolling ability when it is born. • Tongue rolling is a dominant trait. Non tongue rolling is recessive. • If the mother is heterozygous and the father is heterozygous- what are their chances of having a child with the tongue rolling ability?

  35. Punnett Example: Rr x Rr R r Genotypes: 25% Homozygous Dominant 50% Heterozygous 25% Homozygous Recessive RR Rr R Rr rr r Phenotypes 75% Tongue Rolling 25% Non-tongue Rolling R= Tongue Rolling r= Non-tongue Rolling

  36. Genetics Websites • OLogy: The Gene Scene

  37. Genetics: Practice • Complete p. 15: Is there a Black Sheep in the Family?

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