DNA Replication, Gene Expression, and Recombinant DNA

DNA Replication Process

DNA replicates just before cell division, ensuring daughter cells inherit the same genetic information as the stem cell. Genetic information is transmitted via genes. In general, each DNA strand serves as a template. Specific enzymes, known as DNA polymerases, join nucleotides one by one. A new chain is formed that is complementary to the template and identical to the chain that was previously attached to it. This process results in two double-stranded DNA molecules.

On occasion, errors occur during DNA replication that give rise to mutations. Some mutations can lead to certain types of diseases. The extraordinary importance of base complementarity allows DNA strands to be copied from a stem cell to a daughter cell, and this property is largely the basis for many current molecular biology techniques.

DNA and Genetic Information

Proteins are large molecules formed by the joining of amino acids. Each protein is characterized by its unique sequence, structure, and various functions: some form structural components, while others regulate and coordinate the functions of organs. Proteins are biologically active molecules responsible for the characteristics that give each individual their specificity.

Gene Expression: Transcription and Translation

Protein synthesis takes place in ribosomes located in the cell's cytoplasm. RNA consists of single-stranded nucleotides and has the same bases as DNA, except that thymine is replaced by uracil. Uracil pairs with adenine.

The RNA synthesis process is called transcription. RNA leaves the nucleus carrying the genetic message to direct the synthesis of proteins; this RNA is called messenger RNA (mRNA).

Once in the cytoplasm, the mRNA binds to a ribosome, which reads and translates the message to synthesize a protein. This process, known as translation, uses a genetic code that maps the equivalence between the language of RNA and the language of proteins. Each group of three RNA bases is called a codon, and each codon corresponds to one of the 20 amino acids.

Recombinant DNA Technology

Recombinant DNA technology encompasses techniques that allow for the manipulation of DNA. A DNA fragment of interest, originating from a donor organism, can be inserted into another DNA molecule, known as a vector. The resulting molecule, with a new combination of the inserted DNA and the vector, is called recombinant DNA. Essentially, recombinant DNA is any DNA molecule formed by joining DNA segments of different origins.