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Basic Genetics - the Study of Heredity -

Basic Genetics - the Study of Heredity -. Betsy Sanford 7 th Life Science Lost Mountain Middle School. trait – are hereditary (passed from parent to offspring through DNA) DNA – the chemical code for building proteins proteins – create cell structure and function

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Basic Genetics - the Study of Heredity -

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  1. Basic Genetics- the Study of Heredity - Betsy Sanford 7th Life Science Lost Mountain Middle School

  2. trait – are hereditary (passed from parent to offspring through DNA) • DNA – the chemical code for building proteins • proteins – create cell structure and function • chromosomes – threadlike strands of DNA • genes – sections of chromosomes that code for specific proteins • humans – about 20-25,000 genes on 46 chromosomes

  3. DNA Diagrams

  4. DNA Diagrams

  5. DNA Diagrams

  6. Human Chromosomes • 23 pair = 46 total • the last pair determines gender

  7. Gregor Mendel: The Father of Genetics • born 1822 in Austria • college & monastery; worked in gardens • wondered why similar plants had different characteristics. • decided to study pea plants because they grow fast, are self-pollinating, and come in many varieties. • did not know about DNA; made his theories based on the results of his experiments. • in eight years (1856-1864), he grew over 30,000 pea plants

  8. Gregor Mendel: The Father of Genetics

  9. cross-pollination - occurs when pollen from one plant pollinates the egg of another plant

  10. true-breeding – when a plant self-pollinates and always shows the same trait as the parent • Mendel crossed true-breeding plants

  11. Alleles • the different forms of a gene • flower color = purple or white • purple flower color • stronger, dominant • represented with a capital letter • white flower color • recessive, weaker • represented with a lower case letter

  12. Mendel’s Pea Plants

  13. Reginald Punnett • English zoologist and geneticist • created a table that predicts number and variety of genetic possibilities in offspring • the Punnett square is still used today in genetic counseling

  14. Punnett Square • the letters on the inside of the square show the possible offspring

  15. Genes • you get genes from each parent • each pair of genes is represented by a two letter combination • the letter combination shows the possible alleles (forms) of the genes • two capitals, PP • two lower case pp • or one capital and one lowercase Pp • always write the capital letter first

  16. Genotype • the exact genetic make up of the gene (the exact 2 alleles) • represented by the letter combinations • PP, Pp, pp

  17. Phenotype • the results of the genotype • what the letters show • what you can see of the trait • PP = purple flower color • Pp = purple flower color • pp = white flower color

  18. Homozygous • the alleles of a gene are exactly the same • PP = homozygous dominant • pp = homozygous recessive • also called purebred

  19. Heterozygous • the alleles of the gene are different • Pp = heterozygous dominant • also called hybrid

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