Question

There is no DNA in :
A. Hair root
B. An enucleated ovum
C. Mature RBCs
D. A mature spermatozoan

Answer 1

Hint:- In eukaryotes DNA is present within three organelles Nucleus, Mitochondria and Cytoplasm the nucleus present in cytoplasm and mitochondria is called extra nuclear DNA. While in prokaryotes DNA is present mostly in the nuclear region. In some cells initially nucleus is present but during maturation nucleus is removed for example in sieve tube cells.

Complete answer:
DNA is Bio-macromolecule. DNA in full form Deoxyribonucleic acid was discovered by Friedrich Miescher he named it nuclein DNA helps in storing, translating and preserving the genetic information. DNA exhibits all the properties of ideal genetic material. DNA provides scope for slow changes like mutation.
In eukaryotes DNA is present in three cell organelles
1. Nucleus
2. Mitochondria
3. Chloroplast
While in prokaryotes DNA is mostly located in the nuclear region with help of some basic proteins and called the nucleoid.
A) Hair root : Hair follicles present at the base of DNA contain cytoplasmic DNA.
B) An enucleated ovum : Chromatin material that is composed of DNA, RNA and some proteins.
In fact chromatin is a complex of DNA and proteins and chromatin material is present inside the nucleus, so if Nucleus is removed then nuclear DNA is absent in Cytoplasm but in eukaryotes DNA is also present in Mitochondria of ovum so this option is not correct.
C) Mature RBC : A mature RBC also known as erythrocyte is biconcave in shape except in camels RBC is oval in shape RBC is formed inside the bone marrow after the synthesis nucleus is removed this process is called enucleation. Enucleation is an adaptation of RBC for getting more space for accommodation of haemoglobin so that maximum transport of RBC is achieved.
D) A mature spermatozoan : The head region of the spermatozoan contains DNA so this option is not correct.
So the correct option is (C).

Note:-
- Most RBC’s are biconcave in shape and enucleated but in camels RBC is oval in shape and nucleated.
- In most of the organisms DNA is the genetic material but in some or other organisms RNA also acts as genetic material.
- The double stranded structure of DNA was given by Watson and Crick. The strands of DNA wound helically run antiparallel to each other.
- The structure of DNA contains Pentose sugar, Nitrogenous bases, Phosphate group.