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Chromosome 7 pair in human male karyogram. Chromosome 7 is one of the 23 pairs of chromosomes in humans, who normally have two copies of this chromosome. Chromosome 7 spans about 160 million [ 4 ] base pairs (the building material of DNA) and represents between 5 and 5.5 percent of the total DNA in cells.
Karyotype of a human with Trisomy 21 (Down syndrome). Trisomies can occur with any chromosome, but often result in miscarriage rather than live birth.For example, Trisomy 16 is most common in human pregnancies, occurring in more than 1%, but the only surviving embryos are those having some normal cells in addition to the trisomic cells (mosaic trisomy 16). [3]
Euploidy (Greek eu, "true" or "even") is the state of a cell or organism having one or more than one set of the same set of chromosomes, possibly excluding the sex-determining chromosomes. For example, most human cells have 2 of each of the 23 homologous monoploid chromosomes, for a total of 46 chromosomes.
Monosomy. Schematic karyogram of a human, showing the normal diploid karyotype. It shows annotated bands and sub-bands as used for the nomenclature of chromosome abnormalities including partial monosomies. It shows 22 homologous chromosomes, both the female (XX) and male (XY) versions of the sex chromosome (bottom right), as well as the ...
Aneuploidy is the presence of an abnormal number of chromosomes in a cell, for example a human cell having 45 or 47 chromosomes instead of the usual 46. [ 1 ][ 2 ] It does not include a difference of one or more complete sets of chromosomes. A cell with any number of complete chromosome sets is called a euploid cell.
Rather than having monosomy, or only one copy, the majority of aneuploid people have trisomy, or three copies of one chromosome. [citation needed] An example of trisomy in humans is Down syndrome, which is a developmental disorder caused by an extra copy of chromosome 21; the disorder is therefore also called trisomy 21. [7]
Trisomic rescue (also known as trisomy rescue or trisomy zygote rescue) is a genetic phenomenon in which a fertilized ovum containing three copies of a chromosome loses one of these chromosomes (anaphase lag) to form a diploid chromosome complement. [1] If both of the retained chromosomes come from the same parent, then uniparental disomy results.
Homologous chromosomes are made up of chromosome pairs of approximately the same length, centromere position, and staining pattern, for genes with the same corresponding loci. One homologous chromosome is inherited from the organism's mother; the other is inherited from the organism's father. After mitosis occurs within the daughter cells, they ...