Human Genetics

  • Human genetics is the study of inheritance as it occurs in humans. It encompasses gene structures, functions and their interactions to cause various physiological traits and diseases.

  • Chromosomes are units of inheritance and humans typically have 23 pairs, a total of 46. These pairs are made up of 22 autosomes and a pair of sex chromosomes (XX for females, XY for males).

  • A gene is a segment of DNA that carries the code for a specific protein that functions in one or more types of cells in the body (blood cells, nerve cells, muscle cells, etc.). These genes are aligned along chromosomes.

  • Genotypes represent the genetic makeup of a human, comprising of all genes, while phenotypes represent observable traits influenced by both genotypes and environmental factors.

  • Humans carry two copies of each gene (one from each parent). If these copies do not match, which is often the case, some genes dominate over others to express certain traits. This forms the basis of dominant and recessive inheritance.

  • Genetic mutations occur when a DNA gene is damaged or changed, altering the genetic instructions. This could lead to diseases or disabilities.

  • Human genetic disorders can occur as a consequence of mutations in a single gene, these are known as monogenic disorders. Polygenic disorders (caused by the combined action of >1 genes) and Chromosomal disorders (caused by changes in the number or structure of chromosomes) are two other types of genetic conditions.

  • Genetic disorders could also be inherited in two main ways: Autosomal (non-sex chromosomes) and Sex-linked (sex chromosomes).

  • Meiosis is a type of cell division that reduces the number of chromosomes in a parent cell by half to produce four sex cells or gametes. This ensures that offspring inherit the correct number of chromosomes from each parent.

  • Mitosis, on the other hand, is the process by which a cell divides into two new identical daughter cells. This plays a key role in the growth and development of human bodies.

  • Genetic testing can identify changes in chromosomes, genes, or proteins that can lead to genetic conditions. Such tests are the basis for prenatal screening and diagnosing inherited diseases.

  • The Human Genome Project, completed in 2003, managed to map out all the genes in the human body, opening a gate towards personalised medicine and a better understanding of how our body works on a cellular level.