1. AP Biology Inheritance, Genes and Chromosomes
Chapter 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
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