1. POPULATIONS and the Bell curve

2. Section 15-1

3. An individual who produces as much melanin as humanly possible has genotype MMLLNN. That person’s phenotype would be to have very dark skin, so brown as to almost appear black. MMLLNN During meiosis the genotype MMLLNN, is reduced to the haploid genotype. As the alleles are segregated from each other, the only possibility for the sperm or egg is MLN. MLN

4. Add the alleles from the sperm (MLN) and the alleles from the egg (MLN) to determine the genotype of the zygote (and the new individual), (MMLLNN) The genotype of all the offspring is MMLLNN. All the offspring have the same phenotype—very dark skin. MMLLNN

5. An individual who produces as little melanin as humanly possible has genotype mmllnn. That person’s phenotype would be to have very light skin, so as to appear so white that the pink of the blood shows through. mmllnn During meiosis, the diploid mmllnn, is reduced to the haploid genotype. As the alleles are segregated from each other, the only possibility for the sperm or egg is mln. mln

6. Add the alleles from the sperm (mln) and the alleles from the egg (mln) to determine the genotype of the zygote (and the new individual) mmllnn The genotype of all the offspring is mmllnn. So all the offspring have the same phenotype—very light skin. Crossing homozygous parents results in offspring with no variation. What happens if the very dark mate with the very light?

7. The genotype of all the offspring is MmLlNn. So all the offspring have the same phenotype—medium skin. What happens if the medium-skinned mate with the medium skinned? MmLlNn Add the alleles from the sperm (MLN) and the alleles from the egg (mln) to determine the genotype of the zygote (and the new individual)

8. MmLlNn MLN MLn MlN Mln mLN mLn mlN mln During meiosis, the diploid (2n) genotype, MmLlNn is reduced to the haploid genotype. As the alleles segregate and assort independently, maximum diversity results.

9. Add the alleles from the sperm (MLN) and the alleles from the egg (MLN) to determine the genotype of the zygote (and the new individual), (MMLLNN)

10. If you count up the number of alleles represented by capital letters, you get the number of alleles that code to make a person’s hair, eyes, or skin darker, because each allele represented by a capital letter causes skin cells to make more melanin (brown pigment)

11. The number of alleles coding for the cells to make melanin determine how genetically dark the individual’s hair, skin, or eyes will be. Count up the alleles and total them in the first square

12. The number of alleles coding for the cells to make melanin determine how genetically dark the individual’s hair, skin, or eyes will be. Count up the alleles and total them in each square.

13. Now, count up the alleles coding for melanin production and total them in each square of the Punnet square

14. Now, fill in the rest of the squares in the Punnet square. Notice there is a pattern to the numbers.

15. Count how many sixes, fives, fours, threes, twos, ones, and zeroes, out of 64, and write the totals in the data table on the next slide.

16. Now, plot the data on the graph, with the numbers of alleles on the x-axis and the number of individuals on the y-axis.

17. 1 6 15 20 15 6 1 Now, plot the data on the graph, with the numbers of alleles on the x-axis and the number of individuals on the y-axis.