Ring chromosome

A **ring chromosome** is when two ends of a chromosome come together and look like a ring. This can happen to any chromosome. It was first discovered in 1926 by American biologist Lilian Vaughan Morgan. There are many different symptoms someone may have if they have a ring chromosome. The most common symptom is a delay in growth. Most of the time, ring chromosomes happen randomly. About 1 in 50,000 people have a ring chromosome.

## Formation

Most of the time, a ring chromosome will happen if the two ends of one chromosome are missing. This allows the ends to combine together to form a ring. Sometimes, the ends of the chromosomes won't be missing, but this is very rare. When this happens, the phenotype (appearance and body) of someone is usually normal. They usually do not know they have a ring chromosome.

Ring chromosomes can be very complicated. Sometimes, small parts of the chromosome may be missing (microdeletion) or there may be a copy of it (microduplication).  Sometimes, someone may have three chromosomes (trisomy) instead of two with the extra chromosome being a ring chromosome.

Any chromosome can be a ring chromosome.

## Ring chromosome syndromes

A **ring chromosome syndrome** is any genetic disorder that is caused by a ring chromosome. About 1 in 50,000 people have a ring chromosome syndrome. The symptoms vary based on which chromosome is the ring chromosome. Most of the time, the symptoms vary widely, even in the same ring chromosome syndrome. However, most syndromes with a ring chromosome affect the way someone's body grows.

### List of ring chromosome syndromes

|Chromosome|Common symptoms|Prevalence|
| --- | --- | --- |
|Ring chromosome 1|Microcephaly (small head), intellectual disability, developmental delay|<1 in 1,000,000|
|Ring chromosome 2|Developmental delay, skeleton issues, genital issues, deformities|<1 in 1,000,000|
|Ring chromosome 3|Developmental delay, intellectual disability, deformities|<1 in 1,000,000|
|Ring chromosome 4|Low birth weight, deformities, heart defects|<1 in 1,000,000|
|Ring chromosome 5|Deformities, heart issues, skeletal issues, intellectual disability|Unknown|
|Ring chromosome 6|Deformities, small eyes, intellectual disability|<1 in 1,000,000|
|Ring chromosome 7|Intellectual disability, genital issues, skin issues, deformities|<1 in 1,000,000|
|Ring chromosome 8|Minor deformities, intellectual disability|<1 in 1,000,000|
|Ring chromosome 9|Developmental delay, intellectual disability, deformities|<1 in 1,000,000|
|Ring chromosome 10|Developmental delay, intellectual disability, microcephaly|<1 in 1,000,000|
|Ring chromosome 11|Developmental delay, intellectual disability, microcephaly|<1 in 1,000,000|
|Ring chromosome 12|Heart issues, intellectual disability, developmental delay, microcephaly|<1 in 1,000,000|
|Ring chromosome 13|Deformities, intellectual disability, developmental delay, genital issues||
|Ring chromosome 14|Epilepsy, intellectual disability|<1 in 1,000,000|
|Ring chromosome 15|Intellectual disability, developmental delay, heart issues, spots of different colored skin|<1 in 1,000,000|
|Ring chromosome 16|Developmental delay, intellectual disability, deformities|<1 in 1,000,000|
|Ring chromosome 17|Intellectual disability, deformities, seizures|<1 in 1,000,000|
|Ring chromosome 18|Developmental delay, intellectual disability, deformities|<1 in 1,000,000|
|Ring chromosome 19|Physical issues, learning disability, intellectual disability|<1 in 1,000,000|
|Ring chromosome 20|Epilepsy|<1 in 1,000,000|
|Ring chromosome 21|Physical issues, intellectual disability, epilepsy|Unknown|
|Ring chromosome X|Symptoms of Turner synrdome||
|Ring chromosome Y|Short height, infertility, ambiguous genitalia, bipolar disorder|Unknown|