Mendel’s Laws of Heredity

1. Mendel’s Laws of Heredity • . Mendel, was the first person to trace the characteristics of successive generations of a living thing. • Genetics • Gametes • Traits • Dominant • Recessive

2. Define the following: • Homozygous • Heterozygous • Dominant • Recessive • Monohybrid cross • Dihybrid cross • Phenotype • Genotype

3. IN HUMANS BROWN EYES (B) ARE DOMINANT OVER BLUE EYES (b).Using a Punnett square, predict the genotypes and phenotypes of the offspring whose parents are both Bb or have heterozygous brown eyes. ______% of homozygous brown eyes _____% of heterozygous brown eyes ______% of homozygous blue eyes Phenotypes ______ % brown eyes ______ % blue eyes

4. Do the same when one parent is homozygous brown and the other is homozygous blue. • ______% of homozygous brown eyes • _____% of heterozygous brown eyes • ______% of homozygous blue eyes • Phenotypes ______ % brown eyes • ______ % blue eyes

5. Do the same thing when one parent is heterozygous brown and the other is homozygous blue. ______% of homozygous brown eyes _____% of heterozygous brown eyes ______% of homozygous blue eyes Phenotypes ______ % brown eyes ______ % blue eyes

6. Problem 1: Predicting combinations of alleles in gametes of plants heterozygous for two traits. • A pea plant is heterozygous for both seed shape and seed color. S is the allele for the dominant, spherical shape characteristic; s is the allele for the recessive, dented shape characteristic. Y is the allele for the dominant, yellow color characteristic; y is the allele for the recessive, green color characteristic. What will be the distribution of these two alleles in this plant's gametes?

7. A. 50% of gametes are Sy; 50% of gametes are sY B. 25% of gametes are SY; 25% of gametes are Sy;25% of gametes are sY; 25% of gametes are sy. C. 50% of gametes are sy; 50% of gametes are SY D. 100% of the gametes are SsYy E. 50% of gametes are SsYy; 50% of gametes are SSYY.

8. A. 50% of gametes are Sy; 50% of gametes are sY • B. Correct! 25% of gametes are SY; 25% of gametes are Sy;25% of gametes are sY; 25% of gametes are sy. Alleles of different genes are assorted independently of each other during the formation of gametes. • C. 50% of gametes are sy; 50% of gametes are SY • D. 100% of the gametes are SsYy • E. 50% of gametes are SsYy; 50% of gametes are SSYY.

9. Which of the following genetic crosses would be predicted to give a phenotypic ratio of 9:3:3:1? A. SSYY x ssyy B. SsYY x SSYy C. SsYy x SsYy D. SSyy x ssYY E. ssYY x ssyy

10. A. SSYY x ssyy All offspring would have genotype of SsYy and a phenotype dominant for both traits. B. SsYY x SSYy All offspring would have genotype of either SSYY, SSYy, SsYY, or SsYy, and a phenotype dominant for both traits. C. SsYy x SsYy Correct!!! D. SSyy x ssYY All offspring would inherit dominant S allele from first parent and dominant Y allele from second parent. All offspring would have genotype of SsYy and a phenotype dominant for both traits. E. ssYY x ssyy All offspring would have the genotype ssYy and a phenotype of dented, yellow-seeded plants.

11. How does this apply to you?Are there other factors? • What does this suggest for observable genetic traits? • Does this apply to certain dispositions in humans for health problems. Cancer, heart disease, diabetes…others? • Write a one page paper on these questions.