i need help wth #12 and #13 both. please answer all parts throughly! thank you (

Question

i need help wth #12 and #13 both. please answer all parts throughly! thank you (:



Alt NEUBAUER You are preparing to plate yeast that you have been growing overnight in your laboratory and you want to determine the cell concentration of the culture. After diluting a small amount of culture 1:10 and loading your hemocytometer, you observe the grid pictured above with your light microscope. 12. What is the cell concentration (cells/ml) of the initial culture pictured in the hemocytometer grid above? (Count the cells on the diagram above, represented by dots.) Show your work, Include al unit 13. Using the culture in #12 above, you want to make 10 plates for UV treatment so you will need 1 ml of final plating culture (100ul of final culture per plate). Estimating that only 10% of yeast cells will survive your UV protocol, calculate the amount of initial cell culture and additional liquid media required to obtain 250 living cells/plate after UV treatment. (Hint: think about this problem in reverse. you need 250 cells/plate after UV, how many do you need per plate befor UV?) ShONyourwort

Explanation / Answer

12) volume of each large square = 1mm x 1mm x 0.1mm = 0.1 mm3 = 10-4cm3

now we know that 1cm3 = 1ml

so 10-4cm3 = 10-4ml

now number of dots(cells) in each large square is A=43 , B=28, C= 38 and D=39

so average number of cells or dots = (43+28+38+39)/4 = 37

that means 10-4ml of sample contain 37 cells

therefore, 1ml of sample will contain =37 x 104 cells

as we have diluted out sample into 1:10

that means dilution factor is 10

Hence initial concentation of cells will be = 37 x 104 x 10 = 37x 105 cells/ml

13) this problem is saying that only 10% of yeast cell will survive upto UV treatment. and we need 250 cells per plate so let us assume we initially used x number of cells per plate, out of which only 250 survive

that means 10% of x = 250 or x= (250x 100)/10 = 2500 cells per plate we need

as we are preparing 10 plates so total cell we need = 2500 x 10 = 25000cells

now from problem 12 we know our primary culture cocentration is 37x 105 cells/ml

so, amount of primary culture we will have to pipette out = 25000/37x 105 = 6.75x10-3ml = 6.75ul

and additional media will required = 1000-6.75 = 993.25ul

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