Lab 02 - Epistasis and hypothesis testing

We developed lab guide 02 of this quarter.

We used F2 genetic corn (corn cobs with yellow, red and purple kernels)  to test whether the phenotypic ratios  (yellow or red/purple kernels) follow the ratios expected from  Mendelian inheritance.  Any statistically significant departure from the expected values is considered as evidence of epistasis.

The hypothesis (no difference between observed and expected values) was tested using the chi-square statistic (χ^2):

χ^2 = Σ [(O-E)^2 / E ],

where O is the observed value, and E the expected value.  The degrees of freedom (d.f.) are defined as n-1, where n is the number of phenotypic categories.  The level of significance was 0.05.

The result (p < 0.05) showed a great departure from the expected values, indicating a strong epistasis.

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Lecture - Mendelian Genetics: Theme variations

We covered the last part of chapter 3, regarding variations to the Mendelian inheritance theme:

• Incomplete dominance
  
• Codominance
  
• Multiple alleles
  
• Gene interactions (including epistasis)
  

We also started talking about chapter 4: Pedigree analyses...

Quiz #2 Qs & As:

1. State Mendel’s principle of segregation

Alleles segregate during gamete formation so that only one allele per gene will be allocated in a gamete

2. State Mendel’s principle of independent assortment

During gamete formation alleles of different genes are assorted independently from each other, so that at zygote formation all possible combinations of alleles are possible (true for genes in different chromosomes)

3. What is recombinant DNA technology?

Using restriction enzymes to isolate fragments of DNA and recombine them with other fragments (usually plasmids to transform bacteria sand clone the DNA fragment) to be studied through a variety of techniques, or used in industry applications

4. What is he goal of a pedigree analysis?

Determine who is in risk of having a genetic condition (providing that it's not obvious) and determining what is the probability of having children affected by that condition (trait)

5. What is codominance?

When two different alleles of a gene are fully expressed in the phenotype

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Lecture - Mendelian genetics (and some theme variations)

We continued talking about Mendelian genetics with the overview of Mendel's classic experiments, and how they lead him to postulate the second of his famous principles

• Principle of Independent Assortment
  

We also mentioned briefly how Mendelian inheritance is studied in humans and how some complex genotypes have to be considered to make sure that some traits inherited in a Mendelian fashion are properly observed.

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