1. Genetic Probabilities
A Day: 5/11
B Day: 5/12

2. Review – Slide 1
Your phenotype is made up of observable traits (your phenotype is showing!)
Traits are characteristics that are inherited (ex: eye color, ear wax consistency)
You receive two alleles for each trait
One allele is from your mom, one allele is from your dad
Dominant alleles are represented using capital letters
Recessive alleles are represented using lower case letters

3. Review – Slide 2
When you receive two of the same alleles, you are homozygous or purebred for that trait
Ex: HH or hh
When you receive two different alleles, you are heterozygous for that trait
Ex: Hh
The representation of your alleles using letters is called a genotype

4. Review – Slide 3
We can use Punnett Squares to make predictions about which traits offspring will receive if we know the genotype of the parents
Meiosis creates genetically unique gametes
The combination of chromosomes in each gamete is RANDOMLY determined due to independent assortment and segregation
Punnett Squares help predict RATIOS of traits within a POPULATION

5. Crossing Organisms
In genetics, the mating of two organisms is called a cross
Examples:
Crossing a purebred white flowered pea plant with a purebred purple flowered pea plant
Crossing a hairless guinea pig with a furry guinea pig
Crossing a population of people with runny ear wax and a population of people with dry ear wax 

6. Crossing Organisms
The parent organisms are called the “Parental Generation” or the “P Generation”
The offspring are called the “First Filial Generation” or the “F1 Generation”
Filia in Latin means “daughter”
When the First Filial Generation is crossed with itself, this creates a Second Filial Generation, or the “F2 Generation”

7. R r R R R R r r R r r r Crossing Organisms
Mom and dad both have the genotype Rr for earwax. Runny earwax is dominant to dry earwax.
Are they heterozygous or homozygous?
Are they purebred or hybrid for the trait?
Does dad have runny or dry earwax?
Fill in the Punnett Square
What RATIO of the offspring have runny earwax?
Identify the P Generation in your Punnett Square
Identify the F1 Generation in your Punnett Square
Identify the Filial Generation in your Punnett Square R r R R R R r r R r r r

8. Carrier Status Brown eyes are dominant to blue eyes
B = Brown Eye Allele
b = Blue Eye Allele
What is the PHENOTYPE for the following GENOTYPES:
Homozygous Dominant?
Heterozygous?
Homozygous Recessive?

9. Carrier Status
When a person is HETEROZYGOUS for a trait, they CAN PASS ON the RECESSIVE allele even though they do NOT show the trait associated with it
A person with the genotype of Bb can pass the blue eyed allele to their gametes and as a result have blue eyed children
When this trait is associated with a disease, they are said to be a CARRIER of that disease

10. Carrier Status
Carriers often do not know that they have the allele associated with the recessive disease because the recessive allele is masked by the dominant allele
Can someone be a CARRIER for a DOMINANT trait or disease?
Genotypes for Huntington’s disease: HH or Hh

11. Monohybrid Crosses
Monohybrid crosses examine the inheritance of one specific trait
What does the root word “mono” mean?
Traits are reported using ratios for both genotype and phenotype

12. Monohybrid Crosses Phenotype Ratio
Purple to white flowers have a 3:1 ratio
75% of the flowers are purple
How many flowers are purple?
Answering “3” by itself is incorrect. Say, “3 out of 4” instead
Genotype Ratio
1:2:1
Homozygous Dominant : Heterozygous : Homozygous Recessive

13. Dihybrid Crosses
Dihybrid crosses examine the inheritance of TWO specific traits, together
What does the root word “di” mean?
Traits are reported using ratios for both genotype and phenotype

14. Dihybrid Crosses What do the “R” alleles represent? Round peas
What do the “Y” alleles represent?
Yellow peas
What do the “r” alleles represent?
Wrinkled peas
What is the phenotype of a plan that has a RRYY genotype?
Round pea that is also a yellow pea

15. Dihybrid Crosses
Video (starts at 6:47): m47s
Pause at about 9:05 & 9:11
Prepare to fill in your copy of the blank dihybrid cross on your notes!
In the example at the end, what does he mean when he says “you are doing too much work” if you set up a 4x4 Punnett Square?

16. Bikini Bottom Genetics

17. Bikini Bottom Genetics – Check your progress
Answer 1
A - long nose,
B - blue body,
C - squarepants,
D - round eyes,
E - round eyes,
F - stubby nose,
G - roundpants,
h - yellow body
Answer 2
A - Yy & YY,
B - ss,
C - rr,
D - LL & Ll,
E - ll,
F - RR & Rr,
G - SS & Ss,
H - yy
Answer 3
A - Rr,
B - SS,
C - LL,
D - Yy

18. Bikini Bottom Genetics – Check your progress
Answer 4
A - See square at right, Gerdy’s genotype = Ss,
B - BillyBob’s genotype = Ss
C - SS & Ss = squarepants and ss = roundpants
D – Use the Punnett square to answer
E - 75%
F – 25%

19. Bikini Bottom Genetics – Check your progress
Answer 6
The Punnett square shows that they would have a 50%
chance (2 out of 4) for a little sponge with a blue body
color.

20. Bikini Bottom Genetics – WHEN YOU ARE DONE
Keep the paper until next class
Get a book and answer the following EXTRA CREDIT questions
Do problem 4 on 187
Do the “quick lab” on 185
IF YOU FINISH EARLY, THE EXTRA CREDIT IS REQUIRED