Question

1). in what kind of buffer should a DNA sample that was isolated from human cheek cells be stored?

2).What is Lambda max and why is it important?

3) if the pH of a hot tub is too high, say pH 8.0, the. what should be added to bring it to a neutral pH?

4). what color of light has a wavelength of 530nm? if a molecule absorbs light at 530nm, what color could it be ? what color do we know that it is not ?

5). what happens to the absorbance of a sample as the concentration of a sample increases or decreases?

Answer 1

1. DNA sample should be stored in a TRIS buffer agent such as TE, TAE, or TBE. TAE buffer has better conductivity than TBE, so DNA fragments will migrate faster in TAE buffer than TBE. TBE buffer supports better agarose cross-linkage, so you'll get better resolution of large DNA fragments.

2. Lambda max refers to the wavelength in the absorption spectrum where the absorbance is maximum. Generally, molecules absorb in a wavelength range centred around the lambda max.

3. Neutral pH means pH 7 and if the pH is 8 then some acids should be added to reduce the pH to reach the pH 7 or neutral pH. These acids are -  muriatic acid and dry acid (also known as sodium bisulfate).

4. Green colour has a wavelength of 530nm. Thus the colour of the light would be green. Remaining visible spectrum would not pertain to this wavelength.

5. Beer's law relates to the concept of concentration and absorbance. According to this law, absorbance and concentration are directly proportional. Thus if the concentration of a sample increases, absorbance increases and if the concentration of a sample decreases, absorbance would decrease. The beer`s law equation is-

Absorbance = e L c

In this equation, e is the molar extinction coefficient. L is the path length of the cell holder. c is the concentration of the solution.