The Sordaria Cross

Mr. Andersen explains the Sordaria cross, a biological experiment involving the fungi Sordaria fimicola. The video covers the process of meiosis, the life cycle of Sordaria, and the significance of crossing over. It also includes a lab procedure for analyzing genetic recombination and calculating gene distance. The importance of crossing over in genetic variation is highlighted, referencing historical figures like Thomas Hunt Morgan and Alfred Sturtevant.

What is the primary reason Sordaria fimicola is used in AP biology classrooms?

• It is a rare species.

• It is found only in specific regions.

• It is easy to grow and observe meiosis.

• It has a complex life cycle.

In Sordaria, what is the result of meiosis when no crossing over occurs?

• A 2:2:2:2 spore ratio

• A 1:1:1:1 spore ratio

• A 4:4 spore ratio

• A 3:3:2 spore ratio

What is the significance of crossing over in genetic recombination?

• It reduces genetic diversity.

• It eliminates mutations.

• It creates new chromosomes.

• It prevents gene linkage.

Which pattern indicates crossing over has occurred in Sordaria?

• 5:3 spore ratio

• 3:3:2 spore ratio

• 2:2:2:2 spore ratio

• 4:4 spore ratio

How is the gene distance from the centromere calculated in Sordaria?

• By dividing the crossover percentage by 2

• By subtracting the crossover percentage from 100

• By multiplying the crossover percentage by 2

• By adding the crossover percentage to 50

Why is a larger sample size important in the Sordaria lab experiment?

• To simplify the calculations

• To reduce the time needed for the experiment

• To ensure the spores are visible

• To increase the accuracy of the data

What is the accepted value for the gene distance from the centromere in the lab book?

• 20 map units

• 26 map units

• 30 map units

• 35 map units