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Homework Help: Biochemisty
Posted by Rin on Thursday, March 20, 2014 at 10:47am.

The DNA alpha-helix structure has 566900 complete turns. The average molar mass of one base pair of nucleotides in DNA is approximately 469 g/mol. If the spacing between successive base pairs is about 0.69 nm, and a complete turn in the helical structure of DNA occurs every 6.9 nm, calculate molar mass of DNA molecule. [Answer: 2.66 x 10^9 g/mol]

I just need the steps on how to solve problems like this. Please help and thanks in advance.

molar massDNA=massonebase*6.9/.69*566900

To solve this problem, you will need to use some basic formulas and conversion factors. Here are the steps to solve this problem:

Step 1: Determine the number of base pairs in the DNA molecule.
The number of base pairs can be determined by dividing the total length of the DNA helix by the spacing between successive base pairs. In this case, the total length of the helix is given as 566900 complete turns, and each turn occurs every 6.9 nm. Therefore, the total length is:
Total Length = Number of turns x Spacing between turns
Total Length = 566900 x 6.9 nm

Step 2: Convert the total length to meters.
Since the molar mass of the nucleotides is given in grams per mole, it is important to convert the total length from nanometers to meters. This can be done by dividing by a conversion factor:
Total Length in meters = Total Length in nm / 10^9 nm/m

Step 3: Calculate the mass of the DNA molecule.
The mass of the DNA molecule can be calculated by multiplying the total length (in meters) by the average molar mass of one base pair of nucleotides. In this case, the molar mass is given as 469 g/mol, so the mass of the DNA molecule is:
Mass of DNA molecule = Total Length in meters x Molar mass of one base pair

Step 4: Convert the mass of the DNA molecule to grams.
Since the molar mass is given in grams per mole, you may need to convert the mass of the DNA molecule to grams by dividing by a conversion factor:
Mass of DNA molecule in grams = Mass of DNA molecule in g/mol / 10^9 g/mol

Step 5: Calculate the molar mass of the DNA molecule.
Finally, divide the mass of the DNA molecule in grams by the number of moles to find the molar mass of the DNA molecule, which is your answer.

By following these steps and plugging in the given values, you should be able to calculate the molar mass of the DNA molecule as 2.66 x 10^9 g/mol.