# Probability and Genetics pg

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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

Vocabulary probability Punnett square phenotype genotype homozygous
heterozygous codominance

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!

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

Heads up Tails up -equally likely to occur

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 %

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.

? 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 ?

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

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

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%

You can predict 100 % will be Red
AA aa

Organism with Bb alleles

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

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 =

Pink Reindeer ! YIKES !

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.

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?