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CM000683 (FASTA) Chromosome 21 is one of the 23 pairs of chromosomes in humans. Chromosome 21 is both the smallest human autosome and chromosome, [ 4 ] with 46.7 million base pairs (the building material of DNA) representing about 1.5 percent of the total DNA in cells. Most people have two copies of chromosome 21, while those with three copies ...
Trisomy 21. Down syndrome (also known by the karyotype 47,XX,+21 for females and 47,XY,+21 for males) [98] is mostly caused by a failure of the 21st chromosome to separate during egg or sperm development, known as nondisjunction. [91] As a result, a sperm or egg cell is produced with an extra copy of chromosome 21; this cell thus has 24 ...
Genetics of Down syndrome. Down syndrome is a chromosomal abnormality characterized by the presence of an extra copy of genetic material on chromosome 21, either in whole (trisomy 21) or part (such as due to translocations). The effects of the extra copy varies greatly from individual to individual, depending on the extent of the extra copy ...
Chromosome 1 is the designation for the largest human chromosome. Humans have two copies of chromosome 1, as they do with all of the autosomes , which are the non- sex chromosomes . Chromosome 1 spans about 249 million nucleotide base pairs , which are the basic units of information for DNA . [ 4 ]
Chromosome 2 is one of the twenty-three pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 2 is the second-largest human chromosome, spanning more than 242 million base pairs [4] and representing almost eight percent of the total DNA in human cells. Chromosome 2 contains the HOXD homeobox gene cluster.
Not to be confused with ideogram. A karyotype is the general appearance of the complete set of chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. [ 1 ][ 2 ]Karyotyping is the process by which a karyotype is discerned by determining the chromosome complement of an individual ...
Preimplantation genetic diagnosis. Preimplantation genetic diagnosis (PGD or PIGD) refers to genetic evaluation of embryos and oocytes prior to implantation. When used to screen for a specific genetic condition, the method also makes it possible to select embryos with intersex conditions for termination. Some national authorities, such as the ...
Sex. The XY sex-determination system is a sex-determination system used to classify many mammals, including humans, some insects (Drosophila), some snakes, some fish (guppies), and some plants (Ginkgo tree). In this system, the sex of an individual usually is determined by a pair of sex chromosomes. Typically, females have two of the same kind ...