1. Genetics
Notes 2

2. Monohybrid Crosses Traits can be dominant or recessive
Dominant traits are represented by a capital letter
Recessive traits are represented by a lower case letter
Crossing a single trait
Flower color
Seed shape
Has a predictable outcome
Can use a Punnett squares to show possible outcomes

3. Monohybrid Cross P P p Pp Pp Pp Pp p
Cross of true breeding (homozygous) flower color
Parent generation
Purple – PP
White – pp
All the flowers will be purple
Heterozygous
F1 generation p Pp Pp Pp Pp p

4. Monohybrid Crosses P p P PP Pp p Pp pp Cross between F1 generation
3:1 phenotypic ratio
Three will be purple
One will be white
1:2:1 genotypic ratio
One is homozygous dominant
Two are heterozygous
One is homozygous recessive
F2 generation P PP Pp p Pp pp

5. Monohybrid Crosses P p p Pp pp p Pp pp
Cross between F1 generation and a homozygous recessive plant
1:1 phenotypic and genotypic ratio
Half will be purple
Half will be white p Pp pp p Pp pp

7. Crosses Homozygous round seed and a heterozygous round seed
Two heterozygous stem length
Heterozygous green pod and homozygous yellow pod
Two homozygous flower location – one axial, one terminal
Two heterozygous pod shape

8. Probability Probability is used to predict random events Product Rule:
Multiply probabilities
Can only use in independent events
Sum Rule:
Either/Or
Add probabilities

9. Product Rule
What is the probability that you will roll a four and a five?
1/6  4 and 1/6  5
1/6 X 1/6 = 1/36

10. Sum Rule What’s the probability that you will roll a four or a five?
1/6  4 and 1/6  5
1/6 + 1/6 = 2/6 = 1/3

11. Examples
What is the probability of flipping heads and tails back to back?
What is the probability of rolling a 3, a 4, or a 5 at any one time?
What is the probability of a couple having two girls in a row or two boys in a row?

12. Probability from Punnett Squares
What is the probability that a pea plant will be both dominant and homozygous?
Pp X Pp
TT X tt
Yy X yy

13. Probability from Punnett Squares
What is the probability that a pea plant will be either homozygous or heterozygous dominant?
Pp X Pp
TT X tt
Yy X yy