Essential Idea:  Genes may be linked or unlinked and are inherited accordingly.

• Outline answer to each objective statement for topic 10.2 (coming soon)
• Quizlet study set for this topic (coming soon)

At SHS, Topic 10.2 is taught in the following class unit(s):​​​​​​​​​​​​​​

• Meiosis 
• More Complex Genetics ​
• Natural Selection

Statements & Objectives:

10.2.U1  Unlinked genes segregate independently as a result of meiosis.

• State the difference between independent assortment of genes and segregation of alleles.
• Describe segregation of alleles and independent assortment of unlinked genes in meiosis.

10.2.U2  Gene loci are said to be linked if on the same chromosome.

• Define autosome and sex chromosome.
• Describe what makes genes “linked.”

10.2.U3  Variations can be discrete or continuous.​

• Contrast discrete with continuous variation.
• State an example of a discrete variation,
• State an example of a continuous variation.

10.2.U4  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.

10.2.U5  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.

10.2.A1  Completion and analysis of Punnett squares for dihybrid traits.

• 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.
  

10.2.A2  Morgans’s discovery of non-Mendellian ratios in Drosophilia.

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

10.2.A3  Polygenic traits such as human height may be influenced by environmental factors.

• Outline two example environmental factors that can influence phenotypes.
• Compare continuous to discrete variation.

10.2.S1  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.

10.2.S2  Identification of recombinants in crosses involving two linked genes.

• 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.

10.2.S3  Use of 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.

10.2.NOS  Looking for patterns, trends and discrepancies- Mendel used observations of the natural world to find and explain patterns and tends, Since then, scientists have looked for discrepancies and asked questions based on further observations to show exceptions to the rules. For example, Morgan discovered non-Mendellian ratios in his experiments with Drosophilia.

• Describe the trends and discrepancies that led Morgan to propose the idea of linked genes.