1. Gene loci are said to be linked if on the same chromosome.

• State the difference between independent assortment of genes and segregation of alleles.

• Describe segregation of alleles and independent assortment of unlinked genes in meiosis.

2. Unlinked genes segregate independently as a result of meiosis.

• Define autosome and sex chromosome.

• Describe what makes genes “linked.”

3. Variation can be discrete or continuous.

• Contrast discrete with continuous variation.

• State an example of a discrete variation,

• State an example of a continuous variation.

4. The phenotypes of polygenic characteristics tend to show continuous variation.

• Explain polygenetic inheritance using an example of a two gene cross with codominant alleles.

• Outline the use of Pascal’s triangle to determine phenotype frequencies that results from polygenic crosses.

• State that a normal distribution of variation is often the result of polygenic inheritance.

• State example human characteristics that are associated with polygenic inheritance.

5. Chi-squared tests are used to determine whether the difference between an observed and expected frequency distribution is statistically significant.

• State the two possible hypotheses of a statistical test.

• Calculate the chi square value to determine the significance of differences between the observed and expected results of a genetic cross.

• Determine the degrees of freedom and critical value for the chi-square test.

• Draw a conclusion of significance by comparing the calculated and critical chi-square values.

1. Morgan’s discovery of non-Mendelian ratios in Drosophila.

• Determine possible allele combinations in gametes for crosses involving two genes.

• Use correct notation to depict a dihybrid cross between two unlinked genes.

• Construct a Punnett square to show the possible genotype and phenotype outcomes in a dihybrid cross.

2. Completion and analysis of Punnett squares for dihybrid traits. [Alleles are usually shown side by side in dihybrid crosses, for example, TtBb.]

• Describe how Morgan discovered relationship between eye color and sex in Drosophila.

3. Polygenic traits such as human height may also be influenced by environmental factors.

• Outline two example environmental factors that can influence phenotypes.

• Compare continuous to discrete variation.

1. Calculation of the predicted genotypic and phenotypic ratio of offspring of dihybrid crosses involving unlinked autosomal genes.

• Determine the predicted genotype and phenotype ratios of F1 and F2 offspring of dihybrid crosses.

2. Identification of recombinants in crosses involving two linked genes. [In representing crosses involving linkage, show genotypes as vertical pairs seperated by horizontal lines repesenting the chromosomes.]

• Use correct notation to show alleles of linked genes.

• Construct a Punnett square to show the possible genotype and phenotype outcomes in a dihybrid cross involving linked genes.

• Explain how crossing over between linked genes can lead to genetic recombinants.

3. Use of a chi-squared test on data from dihybrid crosses.

• Calculate a chi-square value to compare observed and expected results of a dihybrid genetic cross.

• Using the df and critical chi-square value, determine if there is a significant difference between observed and expected results of a dihybrid cross.