| Activity #5 Genes come in Pairs Ok, so now we know that for a particular trait such as height in pea plants, one way which it may be expressed (tall) can dominate over another way (short). But how can we explain the ratio of � long plants to � short plants which Mendel got in the F2 generation? The only possible answer must be that these traits are determined by a PAIR of factors. Although Mendel didn�t use the word, today we call those factors Genes. Think back to meiosis and fertilization. The offspring receives half of it�s nuclear material from each parent and would therefor get one gene of each pair from one parent and the other gene of the pair from the other parent. The Different forms of genes, which give contrasting expressions to the same trait, are called alleles. They are always located at the same position or locas on the chromosome pair. A. What is Genotype: Example: B. What is Phenotype: Example: Activity #6 Phenotypes and Genotypes Make a chart similar to the one below: Refer to Mendel�s pea experiment (pg. 156 Fig. 10-5) Use any letter to represent each trait, but follow the rules for phenotypes and genotypes. Trait Dom Phenotype Dom Genotype Dom Genotype Rec Phenotype Rec Genotype Plant Height Tall TT Tt Short tt Activity #7 The Punnett-Square Method (pg. 157 Text) A. What is a punnett-square? B. Create a punnett-square for the �P� generation for Act. #3. How many % are tall? How many % in the offspring are short? Phenotype Ratio Genotype Ratio C. Create a punnett-square for the F1 generation cross (same as question above) D. Create a punnett-square for the F2 generation Activity #8 Should this Dog be called spot? Imagine this: A sperm cell from a male dog fuses with an egg cell from a female dog. Each dog�s gamete carries chromosomes. The zygote that results from the fusion of the gametes contains 78 chromosomes on set of 39 chromosomes from each parent. One pair of zygotes� chromosomes are shown below. L L H A Chromosome from a female dog l T H a Chromosomes from a male dog Trait Dominant Gene Recessive Gene Hair Length Short (L) Long (l) Hair Texture Wavy (T) Silky (t) Hair Curliness Curly (H) Straight (h) Coat Pattern Spotted (A) Solid (a) A. Will the new puppy have a spotted coat? Explain. B. Does the female dog have a spotted coat? Explain. C. Does the male dog have a spotted coat? Explain. |