1. Punnett Squares Part1
Unit 10 Lesson 2

2. Remember? Gregor Mendel = Father of Genetics
Used peas to study heredity
Cross fertilization: he crossed two parent plants (P) (purple X white) and got all purple in the first generation (F1)
Self fertilization: he allowed two purple flowers from the first generation (F1) to self-pollinate to produce the second generation (F2)
The end result = 3 purple and 1 white
Purple is dominant and white is recessive.

3. So what?
Mendel concluded that each flower has two alleles (genes) that determine the appearance.
One allele inherited from each parent.
We use letters to represent the alleles:
Uppercase letter = dominant
P = purple
Lowercase letter = recessive
p = white
PP = purple Pp = purple pp = white

4. Allele combinations homozygous: the alleles are the same (identical)
PP = purple pp = white
Other examples: HH hh AA aa
heterozygous: two different alleles for a trait
Pp (in this case the dominant allele P is expressed… so the flower is purple)
Other examples: Hh Tt Aa

5. Alleles continued…
Alleles can be explained in two ways…
genotype: the letters that are used to show the genes.
Examples: PP, Pp, pp
phenotype: what the organism looks like.
Examples: purple or white flowers

6. brown eyes, tall, narrow nose, bald
Now you try!
heterozygous
homozygous
Hh, Aa, Tt, Ww, Aa
genotype
phenotype
brown eyes, tall, narrow nose, bald
hh, aa, TT, WW, AA, aa, BB, bb

7. Punnett squares

8. T = tall plant t = short plant
T T X Tt
T T
T T
T T
T t
T t
T t

9. T T T t T T X Tt 50% T T 50% Tt 100% Tall T T T T T t T t
T = tall plant t = short plant
T T X Tt
T T
50% T T
50% Tt
100% Tall
T T
T T
T t
T t
T t

10. Punnett squares a a