5-24-13
Genetic Notes
Gregor Mendel also continued to experiment on inheritance patterns. He wondered if certain traits depended on other traits. He wondered wether two traits would always appear together or would they segregate differently.
Mendel then ran a separate experiment to see whether two traits are connected. He cross-bred two pure traits (i.e. yellow, round seeds and green, wrinkled seed). He then got the yellow-round seeds in the F1 generation, and the following ratios in the F2 generation: 9RY (round yellow), 3 rY (wrinkled yellow), 3Ry (round green), 1 ry ( wrinkled yellow). This data led to the law of independent assortment. This mean that the traits are not dependent on the others.
Punnett squares can also be used to predict dihybrid cross (two traits). However in this type of punnett squares there are four alleles and sixteen boxes that need to be done. There are usually four phenotypes and four genotypes that can be created.
Mendel then ran a separate experiment to see whether two traits are connected. He cross-bred two pure traits (i.e. yellow, round seeds and green, wrinkled seed). He then got the yellow-round seeds in the F1 generation, and the following ratios in the F2 generation: 9RY (round yellow), 3 rY (wrinkled yellow), 3Ry (round green), 1 ry ( wrinkled yellow). This data led to the law of independent assortment. This mean that the traits are not dependent on the others.
Punnett squares can also be used to predict dihybrid cross (two traits). However in this type of punnett squares there are four alleles and sixteen boxes that need to be done. There are usually four phenotypes and four genotypes that can be created.
Discussion Questions
- What is the law of independent assortment?
- How is a dihybrid cross different from a monohybrid cross?
- Short legs and polydactyly are dominant traits in cats. Show the cross between a cat that is heterozygous for short legs and heterozygous for polydactyly. What is the probability that an offspring will have long legs and more than eighteen toes?
- What is the expected phenotypic ratios of a cross between two organisms that are heterozygous for two traits?
Discussion Answers
- This states that each allele is separate and independent form each other.
- Dihybrid has two genotypes, while monohybrid has one genotypes.
- 1/16th chance.
- 9:3:3:1 of (short, polydactyly):(long, polydactyly):(short, eighteen toes):(long, eighteen toes).