Chromosome Structure Changes
Chromosome structure changes can cause problems with the development, function, and growth of body systems. These changes can disrupt the proteins that the genes make and affect several genes located along the chromosome. These changes can occur during early fetal development, during the formation of sperm or egg cell, or in any cell after birth. Pieces, or small parts, of DNA can be passed between two or more chromosomes or rearranged within a single chromosome. How much of an impact a structural change has will depend on their location and size, and whether or not any genetic material is lost or gained. Some changes will not impact a person’s health at all, while others cause medical problems.
Translocations
This change happens when a part of one chromosome breaks away and attaches itself to a different chromosome. If no genetic material is lost in the cell or gained in the cell, this rearrangement type is described as balance. It is described as unbalanced it there is a loss of genetic material or a gain of genetic material.
Deletions
This change happens when some genetic material is lost due to a chromosome breaking. This can happen anywhere along a chromosome, and can be large or small.
Duplications
This change happens when a piece of a chromosome is duplicated, or copied, too many times. It results in the duplicated segment causing extra copies of genetic material.
Inversions
This chromosome structure change happens when a chromosome breaks in two different places. It results in a part of DNA being re-inserted into the chromosome after being reversed. Genetic material can be lost or not lost after chromosome breakage. When the centromere is involved, is is known as pericentric inversion. When the centromere is not involved and inversion happens in the short arm or long arm, it is known as paracentric inversion.
Dicentric Chromosomes
This type of chromosome contains two centromeres. They occur due to two chromosome pieces abnormally fusing, and each piece contains a centromere. These structures typically include a loss of some genetic material and are unstable.
Isochromosomes
This type of chromosome has two identical arms. It will have two short arms or two long arms, instead of having one short arm and one long arm. Because of this, some chromosomes are lacking copies of other different genes, and some have an extra additional copy of other different genes.
Ring Chromosomes
This type of chromosomes happen when a circular structure is formed when the chromosome arms ends fuse together after a chromosome breaks in two places. The chromosome’s centromere may or may not be included in the ring. In many cases of ring chromosomes, the genetic material located close to the chromosome’s ends is lost.
Resources
University of California, San Francisco. (2010). Three Dimensional Structure of Chromosomes. Retrieved on August 14, 2010 from the University of California, San Francisco: https://www.rbvi.ucsf.edu/Research/sedat/
Genetics Home Reference. (2010). Can Changes in the Structure of Chromosomes Affect Health and Development? Retrieved on August 14, 2010 from Genetics Home Reference: https://ghr.nlm.nih.gov/handbook/mutationsanddisorders/structuralchanges
