Joshua and Esther Lederberg devised a simple technique, called the replica plati
ID: 193839 • Letter: J
Question
Joshua and Esther Lederberg devised a simple technique, called the replica plating method, to test colonies of microorganisms under different growth conditions. A master plate, containing the colonies to be tested, is pressed onto a sterile velvet surface, depositing some cells from each colony in the same pattern as on the master plate. Fresh culture plates are then pressed onto the velvet to pick up cells in the same pattern. The transferred cells can be grown on different media or at different temperatures than the original colonies. Suppose the plates below represent a master plate and two replica plates 1. 1 23 1 23 7 89 Master Plate YPD 30°C Replica Plate SD media 30°C Replica Plate YPD media 37°C NOTE: the numbers represent the colonies. If there is no number, it means that no colony grew in that spot Which of the colonies would you conclude have mutations? What kinds of mutations do you suspect they have (temp. sensitive or auxotrophic)? Explain your reasoning. (4 pts) You pick one of your auxotrophic mutants and test it for growth on minimal media supplemented with the following nutrient pools. (Each row and column is a separate pool. So for example, pool 1 contains alanine, tryptophan and phenylalanine, while pool 4 contains alanine, guanine and threonine.) 2) Pools threonine leucine histidine alanine uanine valine roline tophan 5 6 henylalanine The mutant colony grows on media supplemented with either nutrient pool 2 or 5. What single nutrient does this demonstrate that the mutant is auxotropic for? Explain your reasoning. (2 pts)Explanation / Answer
1.According to joshua and lederberg experiment ,the master plate with YPD media at 30 have 9 colonies but when replica plating done on SD media plate at 30 colony bo 3 and 4 are missing , because SD media is minimal media colony 3 and 4 will not get organic compound which is required for its growth from SD media plate ,.Colony 3 and 4 have auxotrophic mutation and they are not able to synthesize some of organic compound by itself which are important for there growth and sd is minimal media will not able to provide those organic compound .thats why colony 3 and 4 did not grow on SD plate.
On plate containgYPD media at temperature 37 colony 6 and 8 doesnot grow .YPD is providing all the organic compound to microorganisms ,the only thing diffrent is temperature 37 .so the colony 6 and 8 are temperature sensitive and they are not able to grow at 37.
2.According to the given information above the auxotrophic mutant is not able to synthesize valine . When the auxotroph was suplimented with pool 2 and pool 5 saperetly they survived so pool 2 and 5 have only one component similar which is valine, other pool dont have valine and that's why microorganisms will not able to survive. So the auxotroph is not able to synthesize valine.
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