Genetic Recombination and Gene Mapping

Mr. Andersen explains genetic recombination and gene mapping, focusing on Thomas Hunt Morgan's work with fruit flies. Morgan's experiments revealed that genes travel on chromosomes and undergo crossing over, leading to recombination. Despite expecting a 50% recombination rate, Morgan observed only 17%, prompting further investigation. Alfred Sturtevant discovered that genes on the same chromosome have lower recombination rates, leading to the concept of gene linkage. This understanding allowed for the creation of gene maps based on recombination frequencies. Today, DNA sequencing provides precise gene locations, validating Morgan and Sturtevant's findings.

What did Thomas Hunt Morgan use to demonstrate that genes travel on chromosomes?

• Pea plants

• Bacteria

• Fruit flies

• Mice

In Morgan's experiment, what was the genotype of the mutant fruit fly?

• Big B, Big B

• Little b, Little b

• Big B, Little b

• Little b, Big B

What percentage of recombinants did Morgan find in his cross experiment?

• 50%

• 25%

• 17%

• 83%

Who was the student that helped Morgan understand the concept of recombination frequency?

• James Watson

• Alfred Sturtevant

• Francis Crick

• Gregor Mendel

What does a recombination frequency of 17% imply about the distance between two genes on a chromosome?

• They are on different chromosomes

• They are not linked

• They are 17 map units apart

• They are 50 map units apart

What modern technique is used today to map genes on chromosomes?

• DNA sequencing

• Chromosome painting

• Gene cloning

• Gene splicing

What is the significance of a 50% recombination frequency?

• Genes are very close together

• Genes are on different chromosomes

• Genes are on the same chromosome

• Genes are not linked