They contain the information necessary for constructing and organising cells.
Explanation
Deoxyribonucleic Acid (DNA) is the fundamental hereditary material in humans and almost all other organisms. It acts as the blueprint for life, carrying the instructions required for the structure, function, and regulation of the body's cells.- They are found only in the nucleus and nowhere else. is Incorrect: While the majority of DNA is found in the cell nucleus (nuclear DNA), it is not restricted solely to this location. Small amounts of DNA are also present in mitochondria (mitochondrial DNA or mtDNA) and, in plant cells, within chloroplasts. These are known as semi-autonomous organelles.
- They contain the information necessary for constructing and organising cells. is Correct: The primary function of DNA is to store and transmit the genetic information necessary for constructing and organizing cells. This information is encoded in the sequence of nucleotides, which directs the synthesis of proteins and enzymes essential for cellular processes.
- They are composed of lipids and proteins. is Incorrect: DNA is a type of nucleic acid, not a lipid or protein. It is a polymer composed of nucleotide monomers (sugar, phosphate, and nitrogenous base). While DNA associates with histone proteins to form chromatin, the molecule itself is chemically distinct from lipids and proteins.
- They disappear completely during cell division. is Incorrect: DNA does not disappear during cell division. On the contrary, during cell division (mitosis or meiosis), the loose chromatin fibers condense into distinct, visible structures called chromosomes to ensure accurate distribution of genetic material to daughter cells.
Key Takeaway: DNA is a nucleic acid that serves as the genetic blueprint for cellular organization. While primarily located in the nucleus, it is also found in mitochondria and chloroplasts.