Question

Blood stains are found at the site of a murderer. If DNA profiling technique is to be used for identifying the criminal , which of the following is ideal for use.
A. Serum
B. Erythrocytes
C. Leucocytes
D. Platelets

Answer 1

Hint: DNA profiling techniques of blood require DNA sample. Cell which is nucleated is the right option as DNA is present in the nucleus and now you have to crack which is nucleated.

Complete answer:
DNA is the genetic material which is unique to each individual and it is present in the nucleus of the organisms and due to this reason, it is used for DNA profiling technique. Now if we look at the options we need to find the cells which are nucleated which means that there should be presence of nucleus.

Let's start from the above options:
> Option A which is serum, it is the plasma component of blood which does not play a role in clotting. It includes all those proteins which are not used in blood clotting like all electrolytes, antibodies, antigens, hormones etc. Serum is enucleated which means that it does not contain nucleus and therefore this cannot be the correct option as DNA is present in the nucleus,

> Option B which is Erythrocytes. Erythrocytes are red blood cells (RBCs) whose structure is biconcave disc-like and it is without nucleus or you can say it is enucleated. It contains haemoglobin pigment which impart red colour to the blood and it transports oxygen and carbon dioxide to and from the tissues. Since erythrocytes are enucleated therefore it does not have DNA and hence this option cannot be the correct one.

> Option C which Leucocytes. Leucocytes are white blood cells (RBCs) and they are colourless cells which circulate in blood and the body fluids and it is involved to protect the body against illness or diseases. These are responsible for your immunity and you can call them immunity cells. These are nucleated or there is presence of nucleus in it. This option seems correct as Leucocytes are nucleated and DNA is present in the nucleus of organisms.

> Option D is Platelets. Platelets are small colourless cell fragments which are present in our blood, it is responsible to form a clot and to prevent the bleeding too. These are made in bone marrow as bone marrow consists of stem cells which develop into RBCs, WBCs and platelets. Platelets are enucleated i.e., there is absence of nucleus in them. So this option cannot be the correct one.

Hence, the correct answer is option (C).

Note: DNA is present in the nucleus and it is really simple that those cells which are nucleated can only be ideal for DNA profiling. Therefore, from all the above given options only Leucocytes are nucleated as they are large cells with nucleus and all the other cells given are enucleated.