Glossary of terms

Haematopoietic stem cell transplantation (HSCT), also known as bone marrow transplantation, is a medical procedure that involves the administration of healthy haematopoietic stem cells (blood stem cells) to patients with dysfunctional or depleted bone marrow. This procedure is used to generate functional cells that replace dysfunctional ones in cases like immune deficiency syndromes, hemoglobinopathies, blood cancers, and other blood diseases.

Hematopoietic stem cells (HSCs), also called blood stem cells, are a type of stem cell found in the bone marrow. They are responsible for producing all the blood cells in the body, including red blood cells, white blood cells, and platelets. These cells are unique because they can divide to produce new cells but also retain the ability to self-renew and differentiate into the various types of blood cells. This dual capability makes HSCs an important source for cellular therapies, including gene therapies. They can be used to treat a wide range of diseases by introducing genetic material into the patient's cells to correct or compensate for genetic defects.

Homologous chromosomes are a pairs of chromosomes inherited from your parents, one from mother (maternal) and one from father (paternal). The homologous chromosome pairs contain the same genes, at the same site (or loci). These genes can have different forms (or alleles) depending the inheritance.

Homology-Directed Repair (HDR) is a DNA repair mechanism. It is activated in a cell upon damage to double-stranded DNA. During HDR, the damaged DNA site is repaired using homologous DNA as template for precisely restoring the damaged DNA sequence. HDR enables the cells to maintain their genomic integrity (the 'accuracy' of the instructions they contain) and reduce accumulation of mutations.

Scientists can use HDR to introduce changes into the genome. This is done by designing a DNA 'template', and introducing it into the cell. This is usually done using a plasmid (a loop of bacterial DNA). This approach is used to model genetic diseases in the lab.

The Human Genome Project was a scientific effort that aimed to determine the DNA sequence of the entire human genome and to understand the instructions (genes) that make up a person, like reading a giant instruction manual for building a human being. The project begain in 1990, and was completed in 2003.