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Structure and function of genetic information (DNA)

Structure and function of genetic information (DNA)

Nucleic acids play an important role in transmitting genetic information.
There are two types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are pentanucleotides and are made up of nitrogen-containing bases and phosphate groups.

Nucleic acids and the role of genetic information (DNA)

Nucleic acids

Nucleic acids play an important role in transmitting genetic information. There are two types of nucleic acids: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). Nucleic acids are pentose carbohydrates and are composed of nitrogen-containing bases and phosphate groups.

The bases that make up nucleic acids are composed of carbon and nitrogen atoms and come in two types: purines and pyrimidines. both DNA and RNA are made up of four combinations of bases.

  • There are two types of purines, adenine (A) and guanine (G), found in both DNA and RNA.
  • There are two types of pyridines: cytosine (C) and thymine (T) for DNA and cytosine (C) and uracil (U) for RNA.

Gene Structure and Function

The main body of genes is DNA, and RNA accurately reads the base sequence of DNA, which is then used as a template for protein synthesis. DNA, which carries genetic information, accurately duplicates the base sequence and transmits it to offspring.

DNA-protein complex chromatin

Structure of Chromatin

Long threads of DNA exist in the nucleus of the cell, folded and bound to proteins. This DNA-protein complex is called chromatin.

Chromatin plays an important role in gene expression by folding DNA in a regular and compact manner. During cell division, the nuclear membrane disappears and chromosomes are seen condensed.

In chromosomes, DNA is bound to histones in a coiling fashion. Histones come together two molecules at a time to form octamers (histone octamers); each histone octamer wraps around about 146 base pairs of DNA about 1.65 times in a left-handed direction. This structure is called a nucleosome and is the smallest unit of chromatin structure.

The nucleosome consists of eight histones, two each of the four types H2A, H2B, H3, and H4. 1.5 m long DNA is contained in a human cell, and this length of DNA is folded in layers with a certain regularity and exists in the nucleus.

Genetic Composition

DNA replication

DNA has a double helix structure; when DNA is replicated, one of the pairs of DNA strands creates a new piece of DNA. This is called semi-conservative replication.

Double-stranded DNA is linked by hydrogen bonds. During replication, the hydrogen bonds in the parental double-stranded DNA are first broken to form a single strand, which is then split in two to initiate the synthesis of two new strands of DNA. A daughter strand with a complementary sequence is synthesized (double-stranded) using the base sequence of the single-stranded portion as a template. At this time, two new DNA double-strands are formed.

Gene Composition

A gene is part of a single DNA molecule that contains introns, which are non-coding (non-coding portions) sequences between the regions that encode the amino acid sequence for the protein called exons. Intron sequences are not reflected in the protein product. Exons are the genetic parts that determine the amino acid sequence of the protein. The introns and exons are mutually exclusive.

Most genes in the human genome also have at least one (usually several) introns. For many genes, the length of all introns combined is longer than the length of all exons combined.