Chromosome 16 Disorders and Health
Chromosome 16 contains thousands of genes. The role of genes is to guide protein production, which impacts a variety of functions in the body. Unfortunately, many genetic diseases are linked to problems with the genes on chromosome 16.
Changes in the structure or copy number of a chromosome can cause health and developmental problems.
Basics of chromosomes
Chromosomes are the structures that contain your genes, which provide instructions that guide the development and functioning of the body. There are 46 chromosomes, divided into 23 pairs and containing thousands of genes. Within each pair, one is inherited from the mother and the other from the father.
While everyone should have 46 chromosomes in every cell in the body, in rare cases chromosomes can be missing or duplicated, resulting in missing or extra genes. These aberrations can cause health and developmental problems.
The following chromosomal conditions are associated with abnormalities in chromosome 16. These can include an extra copy of chromosome 16, deletions (a section of the chromosome is missing), or duplications (extra parts of the chromosome are present).
In trisomy 16, instead of the normal pair, there are three copies of chromosome 16. Trisomy 16 is estimated to occur in more than 1% of pregnancies, making it the most common trisomy in humans .
Trisomy 16 is incompatible with life and most pregnancies do not progress beyond the first trimester. It is the most common trisomy resulting in miscarriage and the second chromosomal cause of miscarriage, after X-chromosome monosomy (only one copy of the X or Y sex genes).
Trisomy 16 Mosaicism
Sometimes there may be three copies of chromosome 16, but not in all cells of the body (some have both normal copies). This is called mosaicism.
Trisomy 16 mosaicism is compatible with life. Children born with this condition will develop many malformations due to the extra genetic material.
Symptoms of trisomy 16 mosaicism include:
- Poor fetal growth during pregnancy
- Congenital heart defects, such as ventricular septal defect (16% of individuals) or atrial septal defect (10% of individuals)
- Unusual facial features
- Underdeveloped lungs or airway problems
- Musculoskeletal abnormalities
- Hypospadias (urethral opening too low) in 7.6% of boys
There is also an increased risk of preterm birth in infants with trisomy 16 mosaicism.
16p13.3 (16p-) deletion syndrome
In this disorder, part of the short (p) arm of chromosome 16 is missing. Deletion of 16p13.3 has been reported in people with tuberous sclerosis, Rubnstein-Taybi syndrome, and alpha-thalassemia.
Duplicating 16p11.2 (16p+)
Duplication of all or part of the short arm (p) of chromosome 16 can cause:
- Poor growth of the fetus during pregnancy and the infant after birth
- small round skull
- Rare eyelashes and eyebrows
- Round flat face
- Prominent upper jaw with small lower jaw
- Low rounded ears with deformities
- Thumb abnormalities
- Severe mental retardation
16 Q Minus (16q-)
In this disorder, part of the long arm (q) of chromosome 16 is missing. Some people with 16q- may have severe growth and developmental disorders, as well as abnormalities of the face, head, internal organs, and musculoskeletal system.
16q Plus (16q+)
Duplication of all or part of the long arm (q) of chromosome 16 can produce the following symptoms:
- poor growth
- Mental impairment
- Asymmetrical head
- High forehead with prominent or beaked short nose and thin upper lip
- Joint abnormalities
- Genitourinary abnormalities.
16p11.2 Deletion syndrome
This is the deletion of a segment of the short arm of the chromosome of about 25 genes, affecting one copy of chromosome 16 in each cell. People born with this syndrome often have developmental delay, intellectual disability and autism spectrum disorder.
However, some have no symptoms. They can pass this disorder on to their children, which can have more serious effects.
It is a duplication of the same segment 11.2 and may have similar symptoms as the deletion. However, more people with duplication have no symptoms.
As with deletion syndrome, they can pass the abnormal chromosome on to their children who may experience more severe effects.
There are many other combinations of deletions or duplications of parts of chromosome 16.
Further research needs to be conducted on all chromosome 16 disorders to better understand all of their implications for those affected.