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Heredity, Genetics Punnett Squares & Probability Mr. Miller.

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Presentation on theme: "Heredity, Genetics Punnett Squares & Probability Mr. Miller."— Presentation transcript:

1 Heredity, Genetics Punnett Squares & Probability Mr. Miller

2 Lets find out if the two pigeons on the left produce offspring that have the traits of the pigeon on the right

3 To do this we must understand how to use a Punnet Square What is a Punnet Square? A chart that allows us to determine the different genotypes that offspring can inherit from their parents

4 Lets see how to use it First we must get the genotype of each parent Example: T: allele for tallness t: allele for shortness tt – mothers genotype Tt – fathers genotype

5 Now lets set up the Punnet Square Tt t t T T t t tt tt

6 What are the number of genotypes for the traits the offspring can inherit? Tttt Tttt Tt t t The offspring can inherit two sets of genes that will produce a tall phenotype The offspring can inherit two sets of genes that will produce a short phenotype

7 Now lets talk about probability What is probability? Probability is the chance that an event will occur How do you find the probability of an event? You must know: the number of specific events the number of possible events

8 Lets find the probability the child will be tall How many genotypes will produce a tall offspring? Tttt Tttt 2 What are number of possible genotypes? 4 Tt t t

9 Now lets find the probability! Probability = Number of specific event 2 1 Number of possible events 4 2 The probability of having a tall offspring is ½, 1:2, or 50%

10 Now try this one Determine the types of genes an offspring can inherit from parents that have the following genotypes: Zz - father’s genotype Zz - mother’s genotype Z: gene for gray feathers z: allele for white feathers Z Z z z z zz Z Z Z z Z

11 Now lets look at the possible genotypes and the phenotypes that will be expressed Z Z z z z zz Z Z Z z Z There is a single possibility of inheriting a homozygous (pure) dominant genotype which will produce a phenotype with grey feathers There are two possibilities of inheriting heterozygous (hybrid) genotypes which will produce a phenotype with grey feathers

12 Now lets look at the possible genotypes and the phenotypes that will be expressed Z Z z z z zz Z Z Z z Z There is a single possibility of inheriting a homozygous (pure) recessive genotype which will produce a phenotype with white feathers So two grey birds can produce a pigeon with white feathers!

13 Now lets find the probability Lets find the probability the offspring will have grey feathers. = ZZZz zz Z Z z z

14 Now lets find the probability Lets find the probability the offspring will have white feathers. = ZZZz zz Z Z z z


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