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# Ss 10 ss70 ss20 assume that the offspring generation

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Ss= 10% Ss=70% ss=20% Assume that the offspring generation (generation 2) also consists of 1000 squirrels. Assume also that each kind of mating you listed for item 3 contributes equally to this population. Ss=100% SS=30% ss=70% 6. From the percents determined in step 5, what is the expected ratio of straight-haired squirrels to curly-haired squirrels in the offspring? How does this compare to the phenotype of squirrels in generation 1? Thirty percent is straight hair and seventy percent is curly hair, so it compare to it because the numbers are really close to being the same and it shows that a squirrel is more likely to have curly hair. 7. The frequency of any particular characteristic within a group is expressed as a fraction. Thus, in a group of 100 marbles containing 20 red and 80 blue ones, the frequency of red marbles is 20/100 or 1/5 or 20% or 0.2. The frequency of blue marbles is 80/100 or 4/5 or 80% or 0.8. Regardless of how the fractions are written, their sum must always equal 1;

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20/100 + 80/100 = 100/100 = 1 1/5 + 4/5= 5/5 = 1 20% + 80% = 100% = 1 0.2 + 0.8 = 1 In this example, each marble is a gamete and gametes unit randomly. Thus, the frequency of genotype red-red would be 0.2 x 0.2 = 0.04. The frequency of blue-blue would be 0.8 x 0.8 = 0.64. What would be the frequency of the red-blue genotype? The frequency of red-blue would be 0.8 x 0.2 = 0.16. We know that the total of the frequencies of all genotypes must equal 1.0. Therefore, 1.0 - .04 – 0.64 = .32. This means that in the next generation of 100 individuals, we would expect 32 % to be heterozygous. OPTIONAL SECTION 8. Now consider the 2 genes S and s. A. What were their frequencies (expressed as decimals less than one; ex. 0.25) in the original squirrel population? B. What were their frequencies in the offspring generation? (Generation 2) C. How do the gene frequencies in the original population compare with those in the offspring generation? 9. Now make the calculations for a 3 rd generation. A. List the possible genotypes of offspring produced in the 2 nd generation. (Remember heterozygous appears twice) B. Next to each genotype list the possible gametes produced by each. C. Now determine the frequency of all kinds of gametes in this 2 nd generation. Ex. S is what part of the total possible gametes? And s is what part of the total possible gametes? D. Now assume random combination of these gametes. The frequency of S _____ plus the frequency of s _____ represents (=) the total _____ sperm population. Likewise, the frequency of S _____ plus the frequency of s _____ represents (=) the total _____ egg population. Male Gametes Female Gamete 3 rd Generation Total S_____ x S_____ = SS S_____ x s_____ = Ss s_____ x S_____ = Ss s_____ x s_____ = ss 10. Answer the following questions: A. What are the frequencies of each of the 3 genotypes in the 3 rd generation/ B. Assuming that the 3 rd generation consists of 1000 individuals, how many would be homozygous dominant, heterozygous, and homozygous recessive?

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