Lecture 2.2 Competencies and Study Guide
Mendel’s Principle of Segregation
Vocabulary
- Gene
- Genetic locus
- Allele
- Homozygous
- Heterozygous
- Phenotype
- Genotype
- Dominant trait
- Recessive trait
- Random
- Stochastic
- Test cross
Competencies
- Describe the two key questions that Gregor Mendel addressed in his paper introducing his main contribution.
- Describe Mendel’s explanation of the results of his experiments on garden peas (now called the Principle of Segregation), including his answers to both questions identified in the previous competency.
- Explain what portion(s) of that explanation are still part of our modern theory of genetics.
- What is a random process, and how does it differ from a stochastic process?
- Huntington’s disease is a very rare, debilitating disease that affects approximately 1 in 10,000 people. The disease is caused by a particular type of genetic mutation (large number of CAG repeats) in a gene called huntingtin (HTT). Designate the disease-causing allele HTTD and the non-disease-causing allele HTTN. We know that individuals with genotype HTTN will not develop Huntington’s Disease, but people with either HTTD/HTTD or HTTN/HTTD will develop the disease.Which allele is dominant–HTTN or HTTD? Explain your reasoning thoroughly, using the correct definition of dominance.
- Describe Mendel’s Principle of Segregation and explain how his observations demonstrated them.
- Explain why Mendel observed nearly, but not exactly, a 3:1 ratio in the F2 generation.
- Lactase persistence (what people often mistakenly call “lactose intolerance”) is a dominant trait in all mammals, including humans. Mateo has lactase persistence, but his sister, Sophia, does not and neither does their father.What precisely can you say about the genotypes of Mateo and Sophia’s parents?
- Explain how Mendel tested his Principle of Segregation. What were his exact results, and did they support, contradict or say nothing about his hypothesized second principle?