Dna And Rna Macromolecules

DNA and RNA Introduction

DNA and RNA are one of the most significant macromolecules in a cell. The transition of information from DNA to RNA and protein determines absolutely all features of a living cell: its size, shape, function and time of death. There are three main sequential mechanisms, by which this transferring of information occurs within a cell: DNA replication, transcription and translation.

DNA Replication

DNA is a double-stranded macromolecule, which consists of sugar (deoxyribose), phosphate groups, and four types of nucleotides: adenine, thymine, cytosine, and guanine. This molecule also has two different ends: 3’ and 5’; its strands are antiparallel. It is a main storage of genetic information in a cell. Each cell division requires DNA replication. In this process, each strand of a DNA molecule acts as a template for replication. In the result, two new molecules of DNA are synthesized, in which one strand is new and one strand is old.

RNA. Transcription and Translation

Expression of information coded in DNA requires synthesis of RNA molecules. Though, there are some similarities in the structure of both macromolecules, there are significant differences which determine their different functions. For instance, sugar molecule in RNA is ribose, not deoxyribose, thymine is replaced by uracil, and RNA functions mostly as a single stranded molecule in a cell.

RNA molecules derive from DNA in a process called transcription. There are three main types of RNA: messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA). Information in mRNAs converted from DNA defines the amino acid sequence of a peptide or several peptides. tRNAs deliver amino acids to the growing polypeptide chain during translation according to the mRNA sequence. rRNAs form ribosomes – special organelles, where a protein synthesis takes place (Lehninger,