Key Concepts in Genetics and Molecular Biology
Preformationism
In the 18th century, rudimentary microscopic observation of spermatozoa led to the belief that they contained tiny, fully formed humans called homunculi. It was thought that fertilization simply initiated the growth of these homunculi into individuals.
Epigenesis
With the development of the microscope, it became clear that fertilization involved not only growth but also a series of structural changes leading to the development of a complex organism.
Pangenesis
This theory proposed that every organ in the body of the parents produced small particles, or “gemmules,” that traveled through the blood to the genitals and were then passed on to the offspring.
Germplasm
Germplasm was considered the fluid composed of reproductive tissues. It was believed that this fluid perpetuated the same formation by determining the characteristics of the whole body. A small change in the germplasm would lead to changes in the body.
Mendel’s Laws
Act of Uniformity
When starting with pure breeds (e.g., yellow and green plants), all individuals of the first generation are identical with respect to the character studied.
Law of Segregation
Hereditary factors present in a hybrid separate when gametes form, giving rise to new combinations in subsequent generations.
Independent Transmission Act
When considering two characters at once (e.g., color and texture), the transmission of these characters is independent of each other.
Molecular Biology
Molecular biology studies life at the molecular level. It elucidates the structure of DNA and the processes involved in executing the instructions encoded within it to construct every living organism.
DNA
DNA is a double helix structure formed by two antiparallel strands of nucleotides: adenine (A), thymine (T), cytosine (C), and guanine (G). These bases pair specifically (A with T, and C with G) and are always facing each other.
Gene
A gene is a fragment of DNA that encodes a particular protein.
Recombinant DNA
Recombinant DNA is a molecule formed by joining two heterologous molecules, i.e., from different sources. This term is usually applied to molecules produced artificially and deliberately in vitro by joining DNA from two different organisms that are not normally found together. Introducing recombinant DNA into an organism produces a genetic modification that allows the addition of new DNA, leading to the modification of existing traits or the expression of new ones. For example, it can lead to the production of a protein not normally present in the organism. These proteins produced from recombinant DNA are called recombinant proteins. This process is driven by genetic engineering and differs from genetic recombination that occurs naturally within the cell.
Transcription
Transcription is the synthesis of messenger RNA (mRNA). During this process, the base thymine (T) in DNA is replaced by uracil (U) in RNA. The mRNA undergoes maturation in the nucleus by removing non-coding sequences (introns) and then moves to the ribosomes.
Protein Synthesis (Translation)
Protein synthesis, or translation, is the anabolic process by which proteins are formed from amino acids. It is the next step after the transcription of DNA into RNA. Since there are twenty different amino acids and only four nucleotides in RNA (adenine, uracil, cytosine, and guanine), it is clear that the relationship cannot be one amino acid for each nucleotide, nor for every two nucleotides. The four nucleotides, taken two at a time, yield only sixteen possibilities.
Replication
Replication is the synthesis of two identical copies of DNA, using another DNA chain as a template.
Artificial Insemination
Artificial insemination is any method of reproduction in which sperm is placed in a female using specialized instruments and techniques that replace copulation. The sperm can be placed in the eggs (intrafollicular), uterus, or fallopian tubes.
Genetic Engineering
Genetic engineering involves modifying and manipulating DNA, thereby altering the genome. Techniques exist to modify and manipulate DNA, thus modifying the genome.
Cloning
Cloning is the process of making two identical copies of DNA. Bacteria are often used for this purpose due to their rapid replication rate. However, a drawback is that not all factors can be controlled.
Polymerase
A polymerase is an enzyme capable of transcribing or replicating nucleic acids. They are crucial in cell division (DNA polymerase) and DNA transcription (RNA polymerase).
Gene Mutations
Gene mutations affect a single gene and are caused by changes in one or more nucleotides, or by the loss or gain of nucleotides.
Chromosome Mutations
Chromosome mutations affect the structure of chromosomes. If these mutations occur in somatic cells, they may lead to tumors but will not affect offspring. However, if they occur in reproductive cells, the changes will be passed on to the next generation.
Human Genome
On June 26, 2000, the human genome sequence was discovered after a 10-year project called G4. This is of great importance because genes and diseases are directly linked. The human genome consists of 46 chromosomes, divided into 2 sets of 23. 44 are autosomes, and 2 are sex chromosomes. Approximately 95% of the DNA has no known activity but likely plays an important regulatory role.
Biotechnology
Biotechnology is the science based on the use of living organisms or their components to obtain or modify products, improve plants and animals, and develop microorganisms for specific purposes.
Cloning
Cloning involves creating genetically identical copies. DNA, cells, and organisms can be cloned. DNA cloning can be natural (replication) or performed in the laboratory using polymerase chain reactions. Cell cloning can be natural (mitosis) or performed in the laboratory through cell culture. Organism cloning can be natural (asexual reproduction) or performed in the laboratory through nuclear transfer.
Therapeutic Cloning
Therapeutic cloning, legal in several countries, involves implanting the genetic material of an individual into an egg to obtain stem cells through laboratory culture.
Materials Science
Raw Material
Raw material is the material extracted directly from nature, and its direct use is often impossible.
Processed Material
Processed material is the result of transforming raw materials into useful materials, often considered fixed assets.
Synthetic Materials
Synthetic materials are obtained through a series of artificial transformations.
Search for New Materials
The search for new materials aims to improve the properties of existing materials to facilitate their use, considering economic and environmental factors.
Metals
Metals are chemical elements that are solid at room temperature and good conductors of heat and electricity. All metals rust (except gold, platinum, and nickel) and can be used in pure or alloyed forms. The processes and techniques involved in the extraction of metals are collectively called metallurgy.
Polymers
Polymers are macromolecules consisting of simple molecules repeated thousands of times. They can be classified as:
- Natural: Derived directly from plants and animals.
- Artificial: Modified natural polymers through chemical processes.
- Synthetic: Obtained through controlled polymerization processes.
Nanotechnology
Nanotechnology is the science used to manufacture and control structures and machines at the molecular size. It is capable of building materials atom by atom. Applications include nanocomputers, medical applications, and energy cooperation to combat environmental deterioration.