DNA strand

DNA strand refers to one of the two polynucleotide chains that make up the structure of DNA (deoxyribonucleic acid), which is the hereditary material in humans and almost all other organisms. Each strand of DNA is a long, linear molecule that is composed of a series of nucleotides. These nucleotides consist of a nitrogenous base (adenine [A], thymine [T], cytosine [C], or guanine [G]), a sugar molecule (deoxyribose), and a phosphate group. The sequence of these bases along the DNA strand encodes the genetic information used in the development, functioning, growth, and reproduction of all known living organisms and many viruses.

Structure

DNA is famously known for its double helix structure, first described by James Watson and Francis Crick in 1953, based on the X-ray diffraction images taken by Rosalind Franklin. The two strands of DNA run in opposite directions (antiparallel) and are held together by hydrogen bonds between the paired bases. Adenine pairs with thymine (A-T) and cytosine pairs with guanine (C-G). This complementary base pairing allows for the DNA strands to be copied accurately during DNA replication.

Function

The primary function of DNA strands is to store genetic information. The sequence of nucleotides along a DNA strand is read by cellular machinery to synthesize proteins, which are the workhorses of the cell, carrying out most cellular functions. This process involves two key steps: transcription and translation. During transcription, a segment of the DNA strand is copied into RNA (ribonucleic acid), and during translation, the RNA is used to build proteins based on the sequence of nucleotides.

Replication

DNA replication is the process by which DNA makes a copy of itself during cell division. The double helix structure of DNA allows for a relatively simple replication mechanism. The two strands of the DNA helix are separated, and each serves as a template for the synthesis of a new complementary strand. This semi-conservative replication ensures that each new cell receives an exact copy of the DNA.

Repair

DNA strands can be damaged by various factors, including UV light, radiation, and certain chemicals. Cells have multiple DNA repair mechanisms to fix these damages and maintain the integrity of the genetic information. These repair processes are crucial for preventing mutations, which can lead to diseases such as cancer.