Content Objective: Describe methods for conducting genetic crosses in flowering plants, including the roles of P, F1, and F2 generations, and explain how a Punnett grid is used to predict outcomes. Discuss the mechanisms of pollination and the implications for breeding new plant varieties.
Language Objective: Use scientific terms such as “homozygous,” “heterozygous,” and “alleles” to explain the genotype of an organism and differentiate between genes and alleles when describing inherited traits.
Syllabus Details:
D3.2.16 (HL) —Segregation and independent assortment of unlinked genes in meiosis - "Students should understand the link between the movements of chromosomes in meiosis and the outcome of dihybrid crosses involving pairs of unlinked genes."
D3.2.17 (HL) - Punnett grids for predicting genotypic and phenotypic ratios in dihybrid crosses involving pairs of unlinked autosomal genes - "Students should understand how the 9:3:3:1 and 1:1:1:1 ratios are derived."
D3.2.18 (HL)—Loci of human genes and the polypeptide products
D3.2.19 (HL)—Autosomal gene linkage- "In crosses involving linkage, the symbols used to denote alleles should be shown alongside vertical lines representing homologous chromosomes. Students should understand the reason that alleles of linked genes can fail to assort independently."
D3.2.20 (HL) —Recombinants in crosses involving two linked or unlinked genes - "Students should understand how to determine the outcomes of crosses between an individual heterozygous for both genes and an individual homozygous recessive for both genes. Identify recombinants in gametes, in genotypes of offspring and in phenotypes of offspring."
D3.2.21 (HL)—Use of a chi-squared test on data from dihybrid crosses - "Students should unfderstand the concept of statistical significance the p=0.05 level, null / alternative hypothesis and idea of observed versus expected results."
Activity 1 - Dihybrid Crosses
Activity 3 - Recombinants
Crossing Over Answers from the Lesson Notes
How to Identify Recombinants Video
A. Strengthen Your Skills
B. Expand Your Knowledge