Exploring Crossing-Over in Sordaria Fimicola

Mr. Anderson explains the Sordaria cross, a common experiment in AP Biology. Sordaria is a fungus used to study meiosis and genetic recombination. The video covers the process of meiosis, the life cycle of Sordaria, and how crossing over can be observed in its spores. The lab procedure involves counting spores to determine crossover frequency, which helps calculate gene distance. The importance of crossing over in genetic variation is highlighted, referencing historical figures like Thomas Hunt Morgan.

What type of organism is Sordaria?

• Virus

• Bacteria

• Algae

• Fungi

What is the ploidy of the cells formed at the end of meiosis?

• Tetraploid

• Triploid

• Haploid

• Diploid

What happens if no crossing over occurs in Sordaria?

• All spores are of the same type

• A 4 to 4 spore ratio is observed

• No spores are formed

• A 2 to 2 to 2 to 2 spore ratio is observed

What is the result of a mitotic division following meiosis in Sordaria?

• Reduction of genetic material

• Doubling the number of spores

• Formation of haploid cells

• Formation of diploid cells

How can crossing over affect the genetic makeup of spores?

• It increases the ploidy level

• It does not affect the genetic makeup

• It creates new combinations of genes

• It reduces the number of spores

What is indicated by a 2 to 2 to 4 to 2 spore arrangement?

• No crossing over occurred

• Crossing over occurred at one chiasma

• Crossing over occurred at two chiasmata

• The spores are mutated

What does a high frequency of crossing over indicate about the distance between genes?

• The genes do not influence each other

• The genes are far apart

• The genes are on different chromosomes

• The genes are closely linked

How is the frequency of crossing over calculated in Sordaria?

• By observing the spore color

• By dividing the number of crossing over events by the total number of cells

• By dividing the number of crossing over events by two

• By counting the total number of spores

What is the purpose of pressing the ascus under a glass slide?

• To induce spore formation

• To view the spores more clearly

• To count the spores

• To measure the size of spores

What does the presence of linked genes imply about their genetic behavior?

• They undergo frequent mutations

• They are inherited together

• They are always recessive

• They assort independently