Human Evolution and Genetics
Hominid Evolution
Around 1 to 2 million years ago, the first toolmaker, Homo habilis, appeared in East Africa, marking the dawn of humankind. Following Homo habilis, another hominid, Homo ergaster, emerged and migrated from Africa to Indonesia and China around 1.5 million years ago. This migration led to the evolution of Homo erectus, a hominid reaching heights of up to 1.80 meters, possessing a large head, a carnivorous diet, and mastery of fire. Homo erectus persisted until about 50,000 years ago. Finally, the Neanderthals (Homo neanderthalensis) and Homo sapiens (our species) appeared around 200,000 years ago in Europe. Homo sapiens eventually spread throughout Europe, replacing the Neanderthals.
Protein Synthesis
A protein’s blueprint is encoded within its corresponding gene. Ribosomes in the cytoplasm synthesize proteins based on information carried by RNA. This RNA delivers instructions to the cell for protein production, which carry out cellular functions. The process of protein creation is known as protein synthesis. The initial step is transcription, where information stored in DNA is transferred to an RNA molecule. Messenger RNA (mRNA) is formed based on the two DNA strands and serves as the template for protein synthesis.
Cancer
Cancer encompasses a group of diseases characterized by the excessive production of malignant cells. Most cancers form tumors. Metastasis refers to the spread of cancer cells to distant locations, primarily through the lymphatic or circulatory systems, leading to the growth of new tumors. Invasiveness is the ability of cancer cells to penetrate and spread into surrounding tissues. A malignant tumor is one whose cells can migrate from their original site to establish new tumors elsewhere in the body.
AIDS
The AIDS virus, or HIV, is a retrovirus with RNA instead of DNA. This deadly virus gradually weakens the immune system, which normally protects the body against diseases. HIV is present in bodily fluids such as blood, semen, vaginal fluids, and breast milk. AZT is a drug used to treat individuals infected with HIV. One type of vaccine under evaluation is the DNA vaccine, which involves inserting DNA from the infectious agent into a plasmid and injecting it into the individual to provide protection.
Genes
A gene is a linear sequence of nucleotides in a DNA molecule (or RNA in some viruses). It contains the information needed to synthesize a macromolecule with a specific cellular function, typically a protein, but also mRNA, rRNA, and tRNA. Many genes consist of coding regions (exons) interspersed with non-coding regions (introns) that are removed during RNA processing.
Chromosomes
Chromosomes carry most of the genetic material and determine the organization of life and the inherited traits of each species. All individuals of a species have the same number of chromosomes. Chromosomes are duplicated during cell division and revert to their original state afterward. Chromosomes within a cell vary in size and shape, and each type exists in two copies (2N). During the formation of sex cells, the chromosome number reduces to N. Fertilization of the egg by sperm restores the 2N chromosome number, with N from each parent. In addition to paired chromosomes, there are X and Y chromosomes that determine sex. Females have two X chromosomes, while males have one X and one Y. Sex determination by a single pair of chromosomes explains the roughly equal proportion of males and females.
DNA Structure
DNA is a whitish molecule composed of two long, parallel chains twisted together to form a double helix. Each DNA strand consists of phosphate groups, sugars, and nitrogenous bases. There are four types of bases: adenine, thymine, guanine, and cytosine. The order of these base pairs along the DNA molecule is the key to storing biological information.
Human Genome Project
The Human Genome Project is an international research initiative with the scientific goal of determining the sequence of chemical base pairs that make up human DNA and identifying all human genes from a functional perspective. The human genome is the complete DNA sequence of a human and is divided into 24 fragments. It contains approximately 25,000 to 30,000 different genes. Each gene carries the information necessary for the synthesis of one or more proteins.
GMOs
A transgenic organism, or GMO, is one whose genetic material has been altered by artificially introducing a foreign gene from a completely different organism. Creating transgenic organisms involves mixing genes from different species. Advantages: Targeted gene insertion without affecting other genes, new food production, increased productivity, disease resistance. Disadvantages: Higher levels of toxic residues in food, potential for new allergies, ecological impact on crops.