solve the calculations portion. How Big Is DNA....And How Can It Fit Into A Tiny
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solve the calculations portion.
How Big Is DNA....And How Can It Fit Into A Tiny Cell? Let's calculate how large a single bacterial chromosome is. To do this, we first need to know hovw much DNA there is in a bacterial cell. Then, knowing the average mass of a single base pair (dA:dT or dC:dG) the mass of the chromosome per cell can be calculated. With this information and some simple conversions, the length of the chromosome (in um, mm, cm or meters) can be calculated. It seems that is what just about all the researchers focused on in the early days of DNA work and it is not difficult to determine experimentally. Using a separate piece of paper show all calculations and circle your final results. Methods . Grow IL culture of E. coli bacterial cells and determine the cell density using a spectrophotometer and absorbance or serial dilutions and plate counts CFU/ml . Use a stage micrometer to measure the dimensions of an E. coli cell to the nearest yum . Determine total [DNA] using a colorimetric DNA assay (ex, diphenylamine which reacts with deoxyribose to produce a blue-colored product that can be easily detected and quantified). Criven: .Avogadro's number 6.02 x 10 molecules/mol . 650 Daltons (g/mol or grams/mole) per average DNA base pair (bp) 3.4 A per base pair (rise per base in B-DNA) Assumptions . One genome or chromosome per cell . One chromosome is a single (but very large) molecule . Cells lack plasmid or other extrachromosomal DNA Experimental results: . cell density 1.8 X 10 cells/iml [DNA]9.9 X 10 g DNA per ml Size of average E. coli cell 1 m x 2 um - Calculations 1) Mass of the E. coli genome a) [DNA] per cell (g/cell) b) [DN per chromosome (g/ chromosome) c) mass of E. coli chromosome (Daltons (g/mol or grams/mole) of chromosome 2) Linear length of E. coli genome a) Length in base pairs of a single chromosome (as calculated from measured data)Explanation / Answer
1) Mass of E.coli genome:
A) DNA per cell is calculated as follows,
Cell density = 1.8 × 10^8 cells/ml
Volume occupied by one cell,
= 1/1.8 × 10^8
= 0.556 x 10^-8 ml
1 ml contains 9.9 x 10^-7 g of DNA
So, 0.556 x 10^-8 ml contains,
= 9.9 × 10^-7 × 0.556 × 10^-8
= 5.504 x 10^-15 g of DNA per cell
B) One cell contains one chromosome. So, the mass of DNA in a chromosome is 5.504 x 10^-15 g.
C) 1 gram is 6.022 x 10^23 dalton
So, the mass of E.coli chromosome in dalton is,
= 5.504 × 10^-15 × 6.022 × 10^23
= 33.145 x 10^8
= 3.3145 × 10^9 dalton
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