Molecular Biology and Genetic Inheritance Principles

The Central Dogma of Molecular Biology

Replication: The process by which exact copies are made from DNA.
Transcription: The generation of RNA from DNA.
Translation: Decoding the RNA into proteins.

Once processed in the cell nucleus, RNA molecules may leave for the cytoplasm for subsequent use. There are three types of RNA:

• Messenger RNA (mRNA): This is translated on ribosomes to form a protein.
• Ribosomal RNA (rRNA): This is part of the ribosome and is responsible for reading the message that the messenger RNA brings.
• Transfer RNA (tRNA): This brings amino acids to the ribosomes to be joined to form the new protein.

The Genetic Code and Protein Synthesis

The genetic information—essentially, what proteins are produced at every moment of the life cycle of a cell—is encoded in the nucleotide sequences and must be translated to be used. The information contained in messenger RNA is interpreted using the genetic code. This information is determined by the nitrogen bases.

A sequence of three nucleotide bases (a triplet) is called a codon and carries specific information for an amino acid. For example, the GUA triplet or codon is translated as the amino acid valine, and the CAU triplet is translated as the amino acid histidine.

The transfer RNA carrying the complementary codon, known as the anticodon, will call the corresponding amino acid to the ribosome to form the protein.

Foundations of Basic Genetics

Gene: The basic unit of heredity in living things. It is the set of elements that determine a biological characteristic of an organism. From a molecular standpoint, a gene is a DNA fragment responsible for carrying out a particular function, such as the synthesis of a protein. The gene carries the information for the formation of a protein or a specific character.

Genome: The complete set of genes of an organism.

Alleles: Each form is defined as different information that a gene may represent.

Genotype: The set of alleles of an individual for one or more characters.

Phenotype: Each of the aspects or specific manifestations of a character. It is due to the specific information (alleles) that a living being has and the relationship between them. This information is modified by the action of other alleles and, above all, by the action of the environment.

Phenotype, Genotype, and Environmental Factors

Phenotype = Genotype + Environment

The genotype is broader than the phenotype since not all alleles in our possession are expressed; many are hidden. In this sense, there could be cases of phenotypes that our grandparents possessed, which our parents do not have, and then we manifest again. This indicates the existence of alleles that remained hidden in our parents.