Related Research Articles
Cytogenetics is essentially a branch of genetics, but is also a part of cell biology/cytology, that is concerned with how the chromosomes relate to cell behaviour, particularly to their behaviour during mitosis and meiosis. Techniques used include karyotyping, analysis of G-banded chromosomes, other cytogenetic banding techniques, as well as molecular cytogenetics such as fluorescent in situ hybridization (FISH) and comparative genomic hybridization (CGH).
In genetics, chromosome translocation is a phenomenon that results in unusual rearrangement of chromosomes. This includes balanced and unbalanced translocation, with two main types: reciprocal-, and Robertsonian translocation. Reciprocal translocation is a chromosome abnormality caused by exchange of parts between non-homologous chromosomes. Two detached fragments of two different chromosomes are switched. Robertsonian translocation occurs when two non-homologous chromosomes get attached, meaning that given two healthy pairs of chromosomes, one of each pair "sticks" together.
Chromosome 21 is one of the 23 pairs of chromosomes in humans. Chromosome 21 is both the smallest human autosome and chromosome, with 48 million base pairs representing about 1.5 percent of the total DNA in cells. Most people have two copies of chromosome 21, while those with three copies of chromosome 21 have Down syndrome, also called "trisomy 21".
Chromosome 6 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 6 spans more than 170 million base pairs and represents between 5.5 and 6% of the total DNA in cells. It contains the Major Histocompatibility Complex, which contains over 100 genes related to the immune response, and plays a vital role in organ transplantation.
Chromosome 13 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 13 spans about 114 million base pairs and represents between 3.5 and 4% of the total DNA in cells.
Chromosome 22 is one of the 23 pairs of chromosomes in human cells. Humans normally have two copies of chromosome 22 in each cell. Chromosome 22 is the second smallest human chromosome, spanning about 49 million DNA base pairs and representing between 1.5 and 2% of the total DNA in cells.
Chromosome 3 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 3 spans almost 200 million base pairs and represents about 6.5 percent of the total DNA in cells.
Chromosome 4 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 4 spans more than 186 million base pairs and represents between 6 and 6.5 percent of the total DNA in cells.
Chromosome 5 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 5 spans about 181 million base pairs and represents almost 6% of the total DNA in cells. Chromosome 5 is the 5th largest human chromosome, yet has one of the lowest gene densities. This is partially explained by numerous gene-poor regions that display a remarkable degree of non-coding and syntenic conservation with non-mammalian vertebrates, suggesting they are functionally constrained.
Chromosome 8 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 8 spans about 145 million base pairs and represents between 4.5 and 5.0% of the total DNA in cells.
Chromosome 9 is one of the 23 pairs of chromosomes in humans. Humans normally have two copies of this chromosome, as they normally do with all chromosomes. Chromosome 9 spans about 138 million base pairs of nucleic acids and represents between 4.0 and 4.5% of the total DNA in cells.
Chromosome 10 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 10 spans about 133 million base pairs and represents between 4 and 4.5 percent of the total DNA in cells.
Chromosome 11 is one of the 23 pairs of chromosomes in humans. Humans normally have two copies of this chromosome. Chromosome 11 spans about 135 million base pairs and represents between 4 and 4.5 percent of the total DNA in cells. The shorter arm is termed 11p while the longer arm is 11q. At about 21.5 genes per megabase, chromosome 11 is one of the most gene-rich, and disease-rich, chromosomes in the human genome.
Chromosome 12 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 12 spans about 133 million base pairs and represents between 4 and 4.5 percent of the total DNA in cells.
Chromosome 14 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 14 spans about 107 million base pairs and represents between 3 and 3.5% of the total DNA in cells.
Chromosome 15 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 15 spans about 101 million base pairs and represents between 3% and 3.5% of the total DNA in cells.
Chromosome 16 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 16 spans about 90 million base pairs and represents just under 3% of the total DNA in cells.
Chromosome 17 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 17 spans more than 83 million base pairs and represents between 2.5 and 3% of the total DNA in cells.
Chromosome 18 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 18 spans about 80 million base pairs and represents about 2.5 percent of the total DNA in cells.
Chromosome 20 is one of the 23 pairs of chromosomes in humans. Chromosome 20 spans around 63 million base pairs and represents between 2 and 2.5 percent of the total DNA in cells. Chromosome 20 was fully sequenced in 2001 and was reported to contain over 59 million base pairs. Since then, due to sequencing improvements and fixes, the length of chromosome 20 has been updated to just over 63 million base pairs.
References
- ↑ Slovak M.L., Theisen A., Shaffer L.G. (2013) "Human Chromosome Nomenclature: An Overview and Definition of Terms." In: Gersen S., Keagle M. (eds) The Principles of Clinical Cytogenetics. Springer, New York, NY doi : 10.1007/978-1-4419-1688-4_3
- ↑ Brothman AR, Persons DL, Shaffer LG (2009). "Nomenclature evolution: Changes in the ISCN from the 2005 to the 2009 edition". Cytogenet Genome Res. 127 (1): 1–4. doi: 10.1159/000279442 . PMID 20110655.