Question

1. The Lederbergs’ experiment was critical in providing the first evidence to support that mutations occur randomly and not as a response to an outside force or need.
   1. Outline the experiment that the Lederbergs conducted including the replica plating data that supported random mutation theory.

2. Explain what the data would have looked like if their experiment supported the physiological adaptation theory.

Answer 1

a) Antibiotics resistance in bacteria is shown by Lederberg replica platting Experiment

Steps:-

1) Petridish was taken in which nutritive medium that is agar is placed.

2) On this agar they cultured bacterial colony , a Master plate is formed in which different type of bacterial colonies was seen.

3)On this master plate , they touched a wooden block with velvet cloth and then put into another plate with only agar.It was like inoculation process.

4) They saw some colonies of bacteria , they are shifted to another plate with only agar and nutritive medium was also there so they will multiply , a replica of masterplate is generated.

5) When they added this new colonies with same process above into new plate , they added penicillin ( antibiotic) with agar.

6) They found some Bacteria that transferred here are multiplyed and some are died.This indicates bacteria that are survived and multiplied here are having resisitance gene against penicillin and died ones are not having this gene.

This Experiment clearly indicates that nature selects that particular orgainsm that are most suited for that particular condition. In this it can be clearly seen that mutations are random not directed It supports Random mutation theory

b) Nature have different types of variation these variations can be advantageous, can not be seen in normal conditions.Penicillin resistance bacteria was there in population before penicillin was added. These did not evolve resistance by exposure of antibiotics.This pre resistance property of bacteria indicates physiological adaptation.