1. Probability and Genetics pg. 656-666
Objectives:
Describe the principles of probability and how Mendel applied them to inheritance
State how geneticists use Punnett squares

2. Vocabulary probability Punnett square phenotype genotype homozygous
heterozygous
codominance

3. How are punnet squares useful to geneticists?
Questions
How are punnet squares useful to geneticists?
What is the difference between a genotype and a phenotype?
A white cow is crossed with a red bull. The calf is neither white nor red, but roan. Explain how this happens!

4. What was the chance of Pettygrove winnng the coin toss?
Probability-the liklihood that a particular event will occur.

5. Heads up Tails up -equally likely to occur

6. Math terms Probability that coin will land heads up is 1 in 2
Probability that coin will land tails up is in 2
1/2 or 50 %

7. Laws of probability is what is ‘likely’ to occur.
Toss a coin 20 times
Likely or Expect: heads up / 10 tails up
Will occur: heads / 9 tails or
8 heads / 12 tails
Laws of probability is what is ‘likely’ to occur.

8. ? Is it more likely to land tails ?
When you toss a coin more than once the results of one toss do not affect the results of the next toss. ?
Is it more
likely to
land tails ?

9. -Still have a 1 in 2 or 50% chance of landing heads.

10. Is ‘Probability’ related to ‘Genetics’ ?
Yes!
It can help predict the results of ‘Genetic Crosses’
Remember Mendel ? (the guy in a dress)
T x T = T T T T
t x t = t t t t
T x t = T T T t /4 will be short , /4 will be Tall

11. Possible combination of alleles that parents can pass on
Cool Tool Punnett Square-shows all the possible combinations of alleles that can result from a genetic cross.
Possible combination of alleles that parents can pass on
Possible combinations of alleles that offspring can inherit
All by chance
4 possible combinations T t T
T T
25%
T t
25% t
T t
25%
t t
25%

12. You can predict 100 % will be RedAA aa

13. Organism with Bb alleles

14. Other Genetic Terms to use
Phenotype-physical appearance, visible traits ex: traits you can see
Genotype-genetic make-up ex: traits you can’t see
Homozygous-identical alleles ex: T T or t t, Not purebred
Heterozygous-two different alleles ex: Tt or hybrid
Phenotype
Genotype
Tall
T T
T t
Short
t t

15. EXCEPTION Remember Mendel only found Dominant and recessive genes
Codominance-alleles are neither dominant or recessive
no masking takes place
Sooooo……..
Red Reindeer + white Reindeer =

16. Pink Reindeer !
YIKES !

17. Probability Quiz
1. An organisms’ genetic makeup , or allele combinations.
2. An organism’s physical appearance, or visible traits.
3. The likelihood that a particular event will occur.
4. Having two identical alleles for a trait.
5. A chart that shows all the possible combinations of alleles that can result from a genetic cross.
6. Having two different alleles for a trait.
7. A condition in which neither of two alleles of a gene is dominant or recessive.

18. 8. How are punnet squares useful to geneticists?
Questions:
8. How are punnet squares useful to geneticists?
9. What is the difference between a genotype and a phenotype?
10. A white cow is crossed with a red bull. The calf is neither white nor red, but roan. Explain how this happens?

19. Answers to Probability Quiz
1. genotype
2. phenotype
3. probability
4. homozygous
5. punnett square
6. heterozygous
7. codominance

20. Answers:
8. Shows possible genetic outcomes of offspring and the probability of each outcome.
9. Phenotype is the physical appearance, Genotype is the genetic makeup.
10. Co dominance.
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