Chromosomal crossover is the process by which two chromosomes, paired up during Prophase I of meiosis, exchange some distal portion of their DNA. Crossover occurs when two chromosomes, normally two homologous instances of the same chromosome, break and then reconnect but to the different end piece. If they break at the same place or locus in the sequence of base pairs, the result is an exchange of genes. This outcome is the normal way for crossover to occur. If they break at slightly different loci, the result can be a duplication of genes on one chromosome and a deletion of these on the other. This is known as an unequal crossover. If chromosomes break and rejoin on opposite sides of the centromere, the result can be one chromosome being lost during cell division. This article is about the biological chromosome. ... In biology, meiosis is the process that transforms one diploid cell into four haploid cells. ... Space-filling model of a section of DNA molecule Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and many viruses). ... Figure 1: Chromosome. ... Two or more structures are said to be homologous if they are alike because of shared ancestry. ... The word locus (plural loci) is Latin for place. In biology and evolutionary computation, a locus is the position of a gene (or other significant sequence) on a chromosome. ... This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... The centromere is a region of a eukaryotic chromosome where the kinetochore is assembled. ... Cell division is the process of a biological cell (called a mother cell) dividing into two daughter cells. ...
Any pair of homologous chromosomes may be expected to cross over three or four times during meiosis. This reduces the genetic linkage between genes on the same chromosome. The genetic variation of a population is thereby increased through chromosomal crossover. Independent assortment is a somewhat related process operating on the complete set of chromosomes. Genetic linkage occurs when particular alleles are inherited together. ... Independent assortment is a term in genetics for the independent segregation and assortment of chromosomes during sexual reproduction. ...
The physical basis of crossing over was first demonstrated by Harriet Creighton and Barbara McClintock in 1931. Barbara McClintock Barbara McClintock (June 16, 1902-September 2, 1992) was considered one of Americas most distinguished cytogeneticists. ... 1931 is a common year starting on Thursday. ...
Genetic recombination is the name given to a large group of reactions during which cellular machinery uses a stretch of DNA to alter or recombine with a similar (homologous) sequence.
Recombination within genes is able to create new alleles, however, it has been assumed this is not the cell's intent, and any changes to gene sequence are believed to be mutations resulting from mistakes during recombination or replication.
Standard linkage analysis was used to confirm that females have a higher recombination rate than males, and males recombine preferentially in the distal regions of the chromosome.
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