Chromosome 2Chromosome 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 and representing almost eight percent of the total DNA in human cells. Chromosome 2 contains the HOXD homeobox gene cluster. Humans have only twenty-three pairs of chromosomes, while all other extant members of Hominidae have twenty-four pairs. It is believed that Neanderthals and Denisovans had twenty-three pairs.
Chromosome 21Chromosome 21 is one of the 23 pairs of chromosomes in humans. Chromosome 21 is both the smallest human autosome and chromosome, with 45 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 of chromosome 21 have Down syndrome, also called "trisomy 21". Researchers working on the Human Genome Project announced in May 2000 that they had determined the sequence of base pairs that make up this chromosome.
Chromosome 5Chromosome 5 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 5 spans about 182 million base pairs (the building blocks of DNA) 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.
ChromosomeA chromosome is a long DNA molecule with part or all of the genetic material of an organism. In most chromosomes the very long thin DNA fibers are coated with packaging proteins; in eukaryotic cells the most important of these proteins are the histones. These proteins, aided by chaperone proteins, bind to and condense the DNA molecule to maintain its integrity. These chromosomes display a complex three-dimensional structure, which plays a significant role in transcriptional regulation.
Y chromosomeThe Y chromosome is one of two sex chromosomes in therian mammals and other organisms. The other sex chromosome is the X chromosome. Y is normally the sex-determining chromosome in many species, since it is the presence or absence of Y that determines the male or female sex of offspring produced in sexual reproduction. In mammals, the Y chromosome contains the gene SRY, which triggers male development. The DNA in the human Y chromosome is composed of about 62 million base pairs, making it similar in size to chromosome 19.
Chromosome 22Chromosome 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 51 million DNA base pairs and representing between 1.5 and 2% of the total DNA in cells. In 1999, researchers working on the Human Genome Project announced they had determined the sequence of base pairs that make up this chromosome. Chromosome 22 was the first human chromosome to be fully sequenced.
Abelian varietyIn mathematics, particularly in algebraic geometry, complex analysis and algebraic number theory, an abelian variety is a projective algebraic variety that is also an algebraic group, i.e., has a group law that can be defined by regular functions. Abelian varieties are at the same time among the most studied objects in algebraic geometry and indispensable tools for much research on other topics in algebraic geometry and number theory. An abelian variety can be defined by equations having coefficients in any field; the variety is then said to be defined over that field.
Cell cycle checkpointCell cycle checkpoints are control mechanisms in the eukaryotic cell cycle which ensure its proper progression. Each checkpoint serves as a potential termination point along the cell cycle, during which the conditions of the cell are assessed, with progression through the various phases of the cell cycle occurring only when favorable conditions are met. There are many checkpoints in the cell cycle, but the three major ones are: the G1 checkpoint, also known as the Start or restriction checkpoint or Major Checkpoint; the G2/M checkpoint; and the metaphase-to-anaphase transition, also known as the spindle checkpoint.
Algebraic varietyAlgebraic varieties are the central objects of study in algebraic geometry, a sub-field of mathematics. Classically, an algebraic variety is defined as the set of solutions of a system of polynomial equations over the real or complex numbers. Modern definitions generalize this concept in several different ways, while attempting to preserve the geometric intuition behind the original definition. Conventions regarding the definition of an algebraic variety differ slightly.
Cell cycleThe cell cycle, or cell-division cycle, is the series of events that take place in a cell that causes it to divide into two daughter cells. These events include the duplication of its DNA (DNA replication) and some of its organelles, and subsequently the partitioning of its cytoplasm, chromosomes and other components into two daughter cells in a process called cell division. In cells with nuclei (eukaryotes, i.e., animal, plant, fungal, and protist cells), the cell cycle is divided into two main stages: interphase and the mitotic (M) phase (including mitosis and cytokinesis).
