1. Chapter 26: Genetics

2. Genes and chromosomes Chromosome Genes Eye color Hair color Skin color Nose size Nose shape Eye shape hair texture Ear size widow’s peak Ear lobes

3. Types of Chromosomes. Sex Cell Body Cell Chromosomes are paired and therefore have two genes for every trait Chromosomes NOT paired

4. A body cell has ___________ genes for every trait. Sex cells only have ________ gene for every trait two One

5. sperm egg Fertilized egg

6. B = b = Child has a gene for BLUE eyes and a gene for BROWN eyes… ???? B b B b Brown eyed Dad Blue eyed Mom

7. What happens when you have a gene for Brown eyes AND a gene for Blue eyes?? A gene that will SHOW the trait A gene that will NOT show the trait if a dominant gene is present. B B = ___________________ B b = ___________________ b b = Brown eyes Blue eyes

8. Terminology: = HOMOZYGOUS Dominant (pure dominant) = HETEROZYGOUS (hybrid) = HOMOZYGOUS recessive (pure recessive) GENOTYPE – a person’s genesPHENOTYPE (physical appearance) Brown eyes Blue eyes

9. B b B b Possible EggsPossible Sperm

10. B b B b Possible EggsPossible Sperm

11. Punnett Square A method for predicting the possible outcomes (offspring) of a genetic cross Mother’s Genes Father’s Genes Bb B b BB Bb Bb bb

12. egg offspring Sperm egg Sperm offspring

13. X B b BB b b B b

14. X b Bb b b B bb B bb B bb B b

15. X Bb B b B B b b B b B b

16. Gregor Mendel: 1865 Austrian monk Father of genetics Botanist Worked with pea plants. Discovered recessive and dominant genes using mathematics Genetics – study of how traits are passed from parent to offspring

17. Mendel’s experiments: G g g GGgg G g G g GGGg gg yellowgreen P1 F1 F2 All green * yellow trait “disappeared”?? 3 green 1 yellow *yellow trait “re-appeared”

18. Mendel repeated this for all the traits of a pea plant. Since the results were the same, he concluded: Mendel used statistics and punnett squares to accurately predict the outcomes of all his possible genetic crosses. TT x TT = all tall TT x Tt = all tall Tt x Tt = ¾ tall, ¼ short Tt x tt = ½ tall, ½ short TT x tt = all tall tt x tt = all short

19. Proving Mendel’s work TT T T T TT TT TT t t t t t t t tt t t t T T T t t 4 tall 3 tall, 1 short 2 tall, 2 short All short