Exploring the Central Dogma, Genetic Engineering, and Immune Responses
Central Dogma of Molecular Biology
The central dogma describes how DNA replicates a part of its message using a messenger RNA (mRNA) molecule. This transcript carries the genetic information used by ribosomes for protein synthesis (translation). An exception to this dogma exists in some viruses, where RNA can produce DNA via reverse transcriptase.
Genetic Code
The genetic code defines the relationship between nucleotides (bases) of a polynucleotide and amino acids. Three bases form a codon, which specifies an amino acid. The genetic code is degenerate, meaning multiple codons can code for the same amino acid. Only methionine and tryptophan have a single corresponding codon. Stop codons (ochre, amber, and opal) signal the end of protein synthesis.
Transposons
Transposons are DNA sequences that can move to different parts of the genome. This can cause mutations and changes in the amount of DNA. There are simple and compound transposons.
Junk DNA
Junk DNA refers to DNA segments that appear to have no function.
Genetic Engineering
Genetic engineering involves isolating and manipulating genes to transfer them between organisms. This allows for the production of specific substances. Bacteria are commonly used, but the applications extend to higher organisms.
Cloning
Cloning is the process of creating genetically identical copies of a molecule, gene, cell, or organism. Molecular cloning involves inserting a DNA fragment into a bacterium’s DNA for replication and further study.
PCR (Polymerase Chain Reaction)
PCR is a technique used to repeatedly duplicate DNA fragments for analysis and use.
Genetic Fingerprinting
Genetic fingerprinting is a set of genetic characteristics that identify an individual with high reliability.
Assisted Reproduction
Assisted reproduction encompasses techniques used to aid reproduction in men and women, including in-vitro fertilization.
Gene Therapy
Gene therapy involves replacing defective or missing genes with functional ones, often using viruses as vectors.
Specific Defenses (Humoral and Cellular Response)
Lymphocytes are white blood cells that recognize specific antigens and produce a specific immune response.
B Lymphocytes
B lymphocytes synthesize antibodies in the presence of antigens. This is associated with the humoral response.
T Lymphocytes
T lymphocytes are responsible for the cellular response. They cause the death of altered cells and regulate the immune system.
Vaccines
Vaccines contain attenuated antigens that generate immunological memory, providing long-term immunity.
Autoimmunity
Autoimmunity occurs when the immune system attacks the body’s own cells. Examples include: serious illness affecting the thyroid, lupus erythematosus, rheumatoid arthritis, juvenile diabetes, multiple sclerosis, myasthenia gravis, and Addison’s disease.
Hypersensitivity
Hypersensitivity is an excessive immune response that damages the body’s tissues. There are four types: anaphylactic, cytotoxic, hypoII, and delayed hypersensitivity.
Cloning (Expanded Definition)
Cloning is the creation of identical copies of a molecule, gene, cell, or organism. Cloning vectors are small, self-replicating DNA molecules.
Humoral Response
The humoral response involves specific antibodies produced against foreign antigens. These antibodies are synthesized by B cells and circulate in body fluids. B cells differentiate in the bone marrow and can produce a vast array of antibodies. Upon antigen recognition, B cells activate and generate specific antibodies. Some activated B cells become plasma cells, producing large amounts of antibodies, while others become memory B cells for future antigen exposure. Cytokines secreted by macrophages enhance B cell activation.