Chromosome 7
Duplication syndrome 7q11.23, a condition that can cause a variety of neurological and behavioral problems, as well as other abnormalities, results from an extra copy of a region on the long arm (q) of chromosome 7. This region is called Williams-Beuren syndrome region (WBSCR) and its elimination causes Williams Syndrome, also known as Williams-Beuren Syndrome. The region, which has a length of 1.5 to 1.8 million base pairs of DNA (Mb), includes 26 to 28 genes. Symptoms include circulatory system problems, language delay and motor and coordination problems accompanied by hypotonia, weak muscle tone, involuntary movements, seizures. They may also present anguish, aggressiveness, challenging behavior, autism, mutism which implies problems of social adaptation.
Alterations in chromosome 7 occur frequently and are responsible for the development of several types of cancer, in particular, changes in this chromosome have been identified in cancers of blood-forming tissue (leukemia) and in cancers of system cells immune (lymphomas). A loss of part or all of a copy of chromosome 7 is common in myelodysplastic syndrome, which is a disease of the blood and bone marrow. People with this disorder have an increased risk of developing leukemia. Mutations occur during the life of the individual. Studies suggest that some genes on chromosome 7 may play critical roles in growth control and cell division. Without these genes, cells could grow and divide too quickly or uncontrollably, resulting in a cancerous tumor.
Several different changes that affect chromosome 7 can cause speech and language disorders related to FOXP2. These changes involve a region of the long arm (q) of chromosome 7 that contains the FOXP2 gene. Speech and language disorder related to FOXP2 is a rare condition. Some people also have delayed motor skills development, such as walking and tying shoelaces and autism spectrum disorders. If other altered genes of chromosome 7 are added to this condition, the disorder known as Russell-Silver Syndrome occurs.
Greig's Cephalopolysyndactyly Syndrome, a disorder that affects the development of the extremities, head and face. These chromosomal changes involve a region of the short (p) arm of chromosome 7 that contains the GLI3 gene. This gene plays an important role in the development of many tissues and organs before birth.
In some cases, Greig's cephalopolysindactyly syndrome results from a rearrangement (translocation) of genetic material between chromosome 7 and some other chromosome. Other cases are caused by the elimination of several genes, including GLI3, from the short arm of chromosome 7. Loss of multiple genes can cause a more severe form of this disorder called Greig's contiguous cephalopolysindactyly gene deletion syndrome. People with this form of the disorder have characteristic developmental problems that involve the limbs, head and face, along with seizures, developmental delay and intellectual disability.
Russell-Silver Syndrome is caused by abnormalities on chromosome 7, a rare condition characterized by slow growth, distinctive facial features, developmental delay, speech and language problems and learning problems. The expression of active genes is what is called genetic imprinting. In these cases it has been found that the person has some duplicate active genes from the mother, while he does not have active genes from the father.
Chromosome 7 abnormalities cause some cases of Saethre-Chotzen syndrome. This rare condition is characterized by premature fusion of certain bones of the skull (craniosynostosis), which prevents the skull from growing normally and affects the shape of the head and face. Chromosomal changes involve a region of the short arm (p) of chromosome 7 that contains the TWIST1 gene. This gene plays an important role in the early development of the head, face and extremities. The chromosomal abnormalities responsible for Saethre-Chotzen syndrome include translocations of genetic material between chromosome 7 and another chromosome, a rearrangement of genetic material within chromosome 7 (inversion) or the formation of an abnormal circular structure called a ring.
Williams syndrome is caused by the removal of genetic material from the critical region of Williams-Beuren (described above). Researchers believe that the characteristic features of Williams syndrome, which include mild or moderate intellectual disability or learning problems, unique personality characteristics, distinctive facial features, and heart and blood vessel (cardiovascular) problems, are probably related to the loss. of several of the genes. in this region. At the moment, the relationship between most of the genes in the deleted region and the signs and symptoms of Williams syndrome is still under investigation.
Some other disorders of chromosome 7 include deletions, translocations or an additional chromosome 7 (trisomy 7).
