Catalyst 1.What is an example of genotype? 1.What is an example of phenotype? 2.Define homozygous. 3.Define heterozygous. BB Bb bb Blue eyes curly hair short Having 2 of the same alleles = BB or bb Having 2 DIFFERENT alleles = Bb

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How can we predict what the offspring of two parents look like?

The principles of probability can be used to predict the outcomes of genetic crosses. What is the probability of landing on heads both times if you flip a penny twice?

H/T First we must figure out all the possible combi- nations of coin flips. Which combos meet our criteria? ¼ = 25% H/T HH HHTT T T

The allele combinations that might result from a genetic cross can be determined by drawing a Punnett Square. How to complete a Punnett Square: 1. Draw the Punnett Square. 2. Place the father's alleles on the top of the Punnett square, one letter per box. 3. Place the mother's alleles on the left side of the square, one letter per box. 4. Drop the father's alleles down into the squares and bring the mother's across. Now you have all possible allele combinations for the offspring. Bb b bB b b B b b b b father = Bb, mother = bb

Solving Genetics Word Problems The steps:The problem: Black fur in guinea pigs is dominant over white fur. If two heterozygous guinea pigs are crossed, what percentage of their children will be black? 1. Read the problem. Underline the known alleles. 3. Circle and/or write down the genotypes of the parents. 4. Set up and solve Punnett Square. 5. Highlight and answer what the question is asking. 2. Choose a letter to represent the alleles in the problem. B = black (dominant) b = white (recessive) parents: Bb x Bb 25% black

Step 5: Highlight and answer what the question is asking. The problem: Black fur in guinea pigs is dominant over white fur. If two heterozygous guinea pigs are crossed, what is the genotypic ratio of their offspring? genotypic ratio = the proportion of offspring with each genotype BB = Bb = bb = 1/4 = 2/4 = 1/4 = 25% 50% There is a 1:2:1 ratio of genotypes

Step 5: Highlight and answer what the question is asking. The problem: Black fur in guinea pigs is dominant over white fur. If two heterozygous guinea pigs are crossed, what is the phenotypic ratio of their offspring? phenotypic ratio = the proportion of offspring with each phenotype black = white = 3/4 = 2/4 = 75% 25% There is a 1:3 ratio of white to black offspring. Phenotypic ratios only care about what the offspring look like!

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Red flowers (R) are dominant to white flowers (r). If a homozygous red flower is crossed with a white flower, what percent of the offspring would be white?

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