Exploring Mendel's Laws of Inheritance and Genetic Patterns

1. Chapter 88.1 Mini Lecture AP Biology Inheritance, Genes and Chromosomes

2. Gregor Mendel • 1822-1884 • Father of genetics • Famous experiment in which he proved heredity by cultivating many varieties of a garden pea

3. Mendel’s Experiment Self fertilized For many generations Cross fertilized He removed stamens off 1 parent and then collected pollen from the other parent and placed it on the pistils Self fertilized

4. Mendel’s conclusions • Traits are passed down from generation to generation • Each trait contains 2 factors (genes) – 1 from each parent • These factors can be represented by letters called alleles • Alleles that are the same are homozygous • Alleles that are different are heterozygous • Dominant traits can mask recessive traits • Dominant traits are represented by capitol letters (you need at least 1 capitol letter) • Recessive traits must have both lowercase letters

5. 2 important terms • Phenotype – physical appearance of the trait (Example – brown hair) • Genotype – alleles that represent the trait (Example – BB, Bb and bb)

6. Mendel’s Law of Segregation • “When any individual produces gametes, the two copies of a gene separate, so that each gamete receives only one copy”

7. Mendel’s Law of Independent Assortment • “Alleles of different genes assort independently of one another during gamete formation”

8. Punnett Squares • Method devised by Reginald Punnett in 1905 that is used to predict allele combinations of offspring.

10. testcross • Is used to determine whether an individual showing a dominant trait is homozygous or heterozygous • The individual in question is crossed with an individual with the recessive trait • Mendel used this method to verify his hypotheses

11. Dihybrid Crosses • Crosses two individuals and two traits • 16 squared punnett square • To get gamete combinations, FOIL needs to be used. • For example if your parent’s genotype is BbHh, then your gamete combinations are • F = BH • O = Bh • I = bH • L = bh This is what Goes on the Outside of Your Punnett Square

12. Dihybrid Example • Example: Cross a homozygous purple flowered, heterozygous green pod pea plant with a white flowered, yellow pod pea plant. (Green is dominant over yellow) (purple is dominant over white) • PPGg x ppgg • Must do Foil to get the gametes! • First, Outer, Inner, Last • PPGg • F = PG • O = Pg • I = PG • L = Pg • FOIL for ppgg are pg, pg, pg and pg • So now take these gametes and place them in the Punnett Square

13. Dihybrid Example PG Pg PG Pg Ppgg Ppgg PpGg PpGg pg PpGg PpGg pg Ppgg Ppgg PpGg PpGg Ppgg pg Ppgg Ppgg pg PpGg PpGg Ppgg Phenotype: 50% Purple Green 50% Purple Yellow Genotype: 50% PpGg, 50% Ppgg

14. Probability • If an event is absolutely certain to happen, its probability is 1 • If it cannot possibly happen, its probability is 0 • All other events have a probability between 0 and 1

16. Every person with an abnormal phenotype has an affected parent. Either all or about half of the offspring in an affected family are affected.

17. Affected people often have 2 parents who are not affected. In affected families, about ¼ of the children of unaffected parents are affected