# What would be the molar concentration of human DNA in a human cell? Consult your teacher.

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**Hint:**Molar concentration is also known as molarity, amount concentration, or substance concentration. It is a procurement to measure the concentration of a chemical species, in particular of a solute in a solution in terms of the amount of substance per unit volume of solution.

**Complete answer:**

Molarity is a standard expression of solution concentration. It utilises the gram molecular weight of a solute to calculate the molar concentration in per litre of solution. Molarity is the number of moles per litre of solution. It holds the unit symbol ${\text{mol}}/{\text{L}}\;$or

\[\;{\text{mol}} \times {\text{ d}}{{\text{m}}^{ - 3}}\]

in the SI unit.

The gram molecular weight of a substance which can be also defined as the term the formula weight is the sum of the combined atomic weights of all atoms present in the molecule and described in grams. As an example, the gram molecular weight of ${\text{NaCl}}$ is equal to the atomic weight. These atomic weights can be found on a periodic table or as a formula weight on the bottle of substance. The atomic weight of ${\text{Na}}$ $22 \cdot 99{\text{g}}$and the atomic weight of ${\text{Cl}}$is $35 \cdot 45{\text{g}}$then the total is $58 \cdot 44{\text{g}}$.

To make one litre of the final solution, one molar $\left( {\text{M}} \right)$solution contains $1 \cdot 0{\text{ GMW}}$ of a substance that is dissolved in water. Hence, a $1{\text{M}}$solution of${\text{NaCl}}$contains

\[58.44{\text{ }}g.\]

So, it can be said a solution with a concentration of $1{\text{mol}}/{\text{L}}$is said to be one molar.

The average molecular weight of a single base pair in a double-stranded DNA is $650{\text{ daltons}}$ and a human DNA contains $3 \cdot 3 \times {10^9}{\text{ base pair}}$. Now the total molecular weight of a DNA will be the multiplication of the number of base pairs with the molecular weight of a single base pair DNA i.e. the molecular weight of Human DNA is $\left( {3 \cdot 3 \times {{10}^9}} \right) \times 650 = 2 \cdot 15 \times {10^{12}}{\text{ daltons}}$ , which is equivalent to $3 \cdot 59 \times {10^{ - 12}}$.

Avogadro number of molecules is one mole. The next is to convert the amount of DNA into moles. As $3 \cdot 3 \times {10^9}{\text{ base pair}}$ of nucleotides are present in Human DNA.

So, the number of moles is $3 \cdot 3 \times {10^9}{\text{ base pair}}$molecules divided by Avogadro number

${\text{Number of moles }} = {\text{ }}\dfrac{{3 \cdot 3 \times {{10}^9}}}{{6 \times {{10}^{23}}}} = 5.5 \times {10^{ - 15}}$

According to the definition of molarity, it is defined as the number of moles of solute per litre of solution hence the molar concentration of human DNA can be calculated by knowing the volume of liquid present in the cell. The volume varies in different cells. The average volume is $5{\text{ picolitres}}$ $(5 \times {10^{12}})$

So, the molarity of DNA in a human cell can be calculated as follows:

**$\dfrac{{5.5 \times {{10}^{ - 15}}}}{{5 \times {{10}^{ - 12}}}} = 0.0011M$**

**Note:**

The molar solution is in a chemical laboratory for the analysis of raw material. Using the molarity or molar concentration the chemical concentration can be measured. Generally, to calculate a molar concentration gram molecular weight is used. Through the above mentioned calculation process, the calculation of the molar concentration of human DNA in a human cell can be done.