Mendel's First Law

Variations to Mendel's First Law

Pedigree Analysis

Mendel's Second Law

Chi-Square Test



Modifier Genes

Penetrance and Expressivity

Study Questions

Mendelian Genetics Overheads

Mendelian Genetics WWW Links

Genetic Topics

Study Questions

1. What two experimental innovations did Mendel use that allowed him to discovery the laws of genetics?

2. What did Mendel conclude from his experiments?

3. Why is Mendel's First Law of Genetics called the Law of Segregation?

4. Why is Mendel's Second Law of Genetics called the Law of Independent Assortment?

5. What type of cross would produce the following genetic ratios?

  • 3:1
  • 1:1
  • 1:2:1
  • 9:3:3:1
  • 1:1:1:1
  • 2:1
6. A short-tailed mutant of mouse was discovered. Multiple crosses of this mouse to normal mice produced 27 normal, long-talied mice and 25 short-tailed mice. A series of crosses among short tailed mice were made and and 21 short-tailed mice and 11 long-tailed mice were produced? Study these results and determine which phenotype is dominant and explain the ratios observed with regards to the genotypes of the parents in each cross.

7. You hypothesized that snapdragon flower color is controlled in a co-dominant manner. You created an F1 population by crossing red and white parents. You selfed the F1 plants and obtained the following ratio: 31 red, 66 pink, and 27 white flowered plants. Perform an analysis of this data to determine if co-dominant gene action is the correct hypothesis.

8. What is the difference between epistasis and pleiotropy?

9. Two corn homozygous, white-seeded corn lines were crossed and all progeny were red-seeded. These red-seeded F1 progeny were selfed, and the population segregated 9 red-seeded:7 white-seeded. Explain these results by determining the number of genes controlling seed coat colors and giving the genotypes of the parents.

10. How does a modifier gene influence the expression of a phenotype?

11. How are penetrance and expressivity related?

Copyright © 2000. Phillip McClean