arB: Applied Queshons You cred thou crente a Stram of ueast that hos mtations: a
ID: 194011 • Letter: A
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arB: Applied Queshons You cred thou crente a Stram of ueast that hos mtations: a mutation in a s tation ina pmem ond a mutor ne,botoin histidine or , growth ke methionine ON up a cuture of this dou to acroentration of 3.2x0qcel5ml rbrsion Induced revarsion AT 20 sec UV : met-1: 4 ×10-5 3 x 101 cquerry of Indeed, reversion | Rrporion % ) SurvivorS (PT). 5x 10-5 O 38 a) You Plate O.Iml from the 10-1 dilution onto each of the followirg platesHow many colonies do you Predict on each plhte f cels are rot exposed to uV light You Show your WorK Ilogic to get Full marks YM+ h You then Platc O-Iml from 10 diltion onto p Plates and expose the cels to 20 Stconds F UN lgIht POw many colonies do ypu expec? VEDP Plates and expose the cels 20Explanation / Answer
The following equations can be used for calculation :
colony forming unit (CFU)/ml = (no. of colonies x dilution factor)/ volume of culture plate -> (1)
propotion of survivors = no of colonies on UV exposed plate/ no of colonies on non UV exposed plate -> (2)
Let the volume of culture plate = 10 ml
a) using equation (1) : no of colonies of double mutant = (CFU/ml x volume of culture plate)/ dilution factor)
= (3.2 x 10^9 X 10)/10^-1) = 3.2x 10^11
No of colonies on YM animal media = 3.2 x 10^ 11
No of colonies on Ym media +methionine=no of colonies X frequency of spontaneous reversion with met= 1.6 x 10^4
No of colonies on YM media : by equation 2 : survival proportion = no of colonies on UV exposed plate/ no of colonies on non UV exposed plate
But, no of colonies on UV exposed reversion with his =3.2 x 10^ 11 x 3 x 10^ -7 = 9.6 x 10^4
hence by equation 2 : no of colonies on YM media + his = 2.52 x 10^ 3
no of colonies on YM media + met+ his = (1.6 x 10^4) + 2.52 X 10^ 3)= 1.85 x 10^-4
b) using equation (1) : no of colonies on non UV exposed = 3.2 x 10^15
using equation (2) : no of colonies when exposed to UV for 20 sec = 8.42 x 10^15
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