Chromosomes carry genes that tell the body on how to grow, develop and work. The usual number of chromosomes in each body cell is 46, or 23 pairs. A child inherits half from their birth mother and half from their birth father.
Chromosome diseases are genetic conditions caused by changes in a person’s chromosomes. They happen when the number or structure of chromosomes changes or when some cells have a different chromosome makeup. These changes can impact how the body grows, develops and works. They can lead to many different health conditions.
Below is a summary of how chromosome changes occur.
Changes in chromosome number:
- Trisomy: This is when there is an extra chromosome. A person has three copies of one chromosome instead of the usual two. That is a total of 47 chromosomes in each cell.
- Monosomy: This is when a chromosome is missing. A person has only one copy of a chromosome instead of two. This is a total of 45 chromosomes in each cell.
Changes in chromosome structure:
- Deletion: When a section of a chromosome is missing or lost.
- Duplication: When a section of a chromosome is copied. This results in extra genetic material.
- Inversion: When a chromosome breaks in two places and the piece between turns upside down and reattaches.
- Ring: When the ends of a chromosome have broken off, then attach to form a circle or ring.
- Translocation: When chromosome material moves to a different location. This happens either by swapping parts with another chromosome or when a whole chromosome attaches to another.
- Mosaicism: This happens when a person has two or more types of cells with different chromosome numbers. For example, some cells may have the usual 46 chromosomes, while others have 47.