Question

Strain A of bacteria is an Hfr strain that can grow on minimal media without added nutrients, but is sensitive to killing by Ampicillin (genotype Hfr Amp^S bob⁺ billy⁺ joe⁺). Strain B of bacteria is an F- strain that is resistant to Ampicillin, and needs the nutrients BOB, BILLY, and JOE added to minimal media in order to grow (genotype Amp^R bob^- billy^- joe^-). You mate these two strains and then interrupt the mating with a blender at various times and plate the bacteria onto different kinds of media.

After 5 minutes of mating, you see bacteria growing on minimal media with Amp, BOB and BILLY (but no JOE).

After 12 minutes you see colonies growing on minimal media with Amp, JOE, and BILLY (but no BOB).

After 22 minutes you see colonies growing on minimal media with Amp, JOE and BOB.

How far apart are the joe and bob genes? Explain your reasoning.

Answer 1

Ans: The joe and bob genes are (12-5) = 7 min far apart.

Ans. Hfr strain 1. Aups. bob + billyt ain Amps. bobt billy Joen joet, & sturin AmpR bob- billy Joe- After 5 min - AMPR Joe + bob billy- 5 After $2 min f t Amp R Joe- bobt billy- Afture 22 min tampr Joe-bob- billyt 22 So, fare The yoe and bob genes are (12-5) = 7 min apart