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Topic: Chromosomal crossover

	ScienceDaily: Chromosomal crossover
		Chromosome Centers Defined And Sequenced For Model Plant (December 29, 1999) -- The serendipitous discovery of a rare mutation and five years of concentrated effort have allowed a team of American and British researchers to define the centromeres of the five chromosomes of...
		Chromosomal crossover -- Homologous recombination is the process by which two chromosomes, paired up during prophase 1 of meiosis, exchange some distal portion of their DNA.
		Chromosome -- The DNA which carries genetic information in cells is normally packaged in the form of one or more large macromolecules called chromosomes.
	www.sciencedaily.com /encyclopedia/Chromosomal_crossover (1550 words)

	Chromosome
		Sexually reproducing species have somatic cells[?] (body cells), which are diploid [2n] (they have two sets of chromosomes, one from the mother, one from the father) or polyploid [Xn] (more than two sets of chromosomes), and germ line cells[?] (reproductive cells) which are haploid [n] (they have only one set of chromosomes).
		During meiosis, the matching chromosomes of father and mother can exchange small parts of themselves (crossover), and thus create new chromosomes that are not inherited solely from either parent.
		Chromosomal aberrations[?] or Partial chromosomal dysplasia [?](malformation), which are usually the result of a defective crossover.
	www.ebroadcast.com.au /lookup/encyclopedia/ch/Chromosome.html (786 words)

	What are Genetic Algorithms?
		Over a period of time, these changes to the chromosomes give rise to species that are more likely to survive, and so have a greater chance of passing their improved characteristics on to future generations.
		However, empirical studies have shown that better results are achieved by a crossover probability of between 0.65 and 0.85, which implies that the probability of a selected chromosome surviving to the next generation unchanged (apart from any changes arising from mutation) ranges from 0.35 to 0.15.
		If we only use the crossover operator to produce offspring, one potential problem that may arise is that if all the chromosomes in the initial population have the same value at a particular position then all future offspring will have this same value at this position.
	www.optiwater.com /optiga/ga.html (763 words)

	Chromosomal Crossover - EvoWiki
		Chromosomal crossover (or simply "Crossing over") is the breaking of one homologous maternal and paternal chromosome, the exchange of corresponding sections of DNA, and the rejoining of the chromosomes.
		Two genes on the same chromosome that are close together are said to be linked and less likely to recombine.
		Recombinase enzymes line up the homologous chromosomes and split the double helices of the two DNA molecules and the two chromosomes are joined by sticking the homologous DNA strans together, creating a holliday junction, holliday intermediate or cross strand exchange.
	wiki.cotch.net /index.php/Crossing_over (326 words)

	Pharmacogenomics
		Deletion is a genetic mutation in which a part of a chromosome or a sequence of DNA is missing.
		Deletions can be caused by errors in chromosomal crossover during meiosis.
		This can be done directly, by analysing the chromosomes or DNA of an individual, or indirectly, by examining the products of their DNA, such as RNA or proteins.
	www.dxsgenotyping.com /pgx.htm (1237 words)

	Chromosomes and Genetic Mapping
		During meiosis, chromosomes can do some fairly interesting things such as losing pieces (deletion), flipping sections up-side down (inversion), and not separating from their homologous partner when they are supposed to (non- disjunction).
		Crossover occurs when homologous chromosomes separate towards the end of the prophase I, but are still attached at a few points along their lengths.
		These chromosome patterns are reversed from the standard pattern usually seen in mammals, and with your understanding of the crossover phenomenon, you can now understand this unusual situation.
	www.accessexcellence.org /AE/AEPC/WWC/1994/chromosomes.html (1790 words)

	Barbara McClintock Summary
		She produced the first genetic map for maize, linking regions of the chromosome with physical traits, and she demonstrated the role of the telomere and centromere, regions of the chromosome that are important in the conservation of genetic information.
		During this period, she demonstrated the presence of what she called the nucleolar organizers on a region on maize chromosome 6, which is required for the assembly of the nucleolus during DNA replication.
		McClintock, Barbara (1945) Neurospora: preliminary observations of the chromosomes of Neurospora crassa.
	www.bookrags.com /Barbara_McClintock (10177 words)

	Chapter 7
		The three types of maps — linkage, chromosomal, and physical — are illustrated in figure 7.1 and are distinguished both by the methods used for their derivation and the metric used for measuring distances within them.
		All mouse chromosomes are defined at the cytogenetic level according to their size and banding pattern (see figures 5.1), and ultimately, all chromosomal assignments are made by direct cytogenetic analysis or by linkage to a locus that has previously been mapped in this way.
		When the chromosomal lesion and the phenotype assort together, from one generation to the next, it is likely that the former causes the latter.
	www.princeton.edu /~lsilver/book/MG7.html (11503 words)

	Crossover - Wikipedia, the free encyclopedia
		Ethernet crossover cable, Ethernet cable in which the transmit and receive pairs are wapped at one end
		Chromosomal crossover, exchange of material between two chromosomes in genetics
		Crossover (music), music that has commercial success in a genre other than that for which it was aimed
	en.wikipedia.org /wiki/Crossover (244 words)

	Solar Research at the High Altitude Observatory
		The first step of the breeding process proper is the application of the crossover operation to the pair of parent chromosomes.
		The crossover operation is what distinguishes genetic algorithms from other adaptive stochastic techniques, and to a large degree is responsible for the efficient exploration capabilities of genetic algorithms.
		Denote now by m(s,t) the fraction of population members containing the schema s in their chromosomes at generation t, let f(s) be their average fitness, and and F be the average fitness of the population as a whole.
	www.hao.ucar.edu /Public/models/pikaia/breeding.html (1202 words)

	Barbara McClintock Biography \| World of Genetics
		Chromosomes are strands of DNA (deoxyribonucleic acid) that contain the genes that pass hereditary traits from one generation to the next.
		They found that this exchange occurred when parts of homologous chromosomes (chromosomes on which particular genes are identically located) were exchanged in the same division that produced sex cells.
		Finally, after two years, she found what she called a controlled breakage in the chromosome and in 1948, she coined the term transposition to describe how an element is released from its original position on the chromosome and inserted into a new position.
	www.bookrags.com /biography/barbara-mcclintock-wog (1178 words)

	Meiosis (Site not responding. Last check: 2007-10-11)
		Chromosomal crossover (or crossing over) is the process by which two
		chromosomes, paired up during prophase 1 of meiosis, exchange some
		Chromosomal crossover - Psychology Wiki - a Wikia wiki
	www.sciencecrawler.net /search/meiosis.html (314 words)

	BIOL B242 CHROMOSOMAL EVOLUTION
		There is usually about one chiasma (causing a crossover) per chromosome arm; perhaps, therefore, chromosome number (like sex) is an adaptation which affects the general level of recombination in the genome.
		Dobzhansky showed cyclical fluctuations of chromosomal polymorphisms with the seasons, and also that different forms were favoured at different altitudes in the mountains.
		Chromosomal evolution may involve an initial period of genetic drift, but this is controversial.
	www.ucl.ac.uk /~ucbhdjm/courses/b242/ChromEvol/ChromEvol.html (2428 words)

	Strand Invasion and DNA Synthesis From the Two 3' Ends of a Double-Strand Break in Mammalian Cells -- McCulloch et al. ...
		Shaded lines denote the length of copied chromosomal sequences, and their termination in dashed lines indicates the position at which copying terminates or at which the known restriction enzyme map ends.
		Strand invasion of the homologous chromosomal duplex (shaded line) by a single-strand, 3'-ending vector tail (solid line) initiates recombination, and ii is accompanied by D-loop displacement.
		In iv, the D loop is further enlarged as copying on both sides of the vector-borne DSB proceeds into regions of nonhomology, and finally, in v, the vector unwinds from the target locus and integrates elsewhere in an ectopic genomic position.
	www.genetics.org /cgi/content/full/163/4/1439 (4486 words)

	BRCA2 Regulates Homologous Recombination in Response to DNA Damage: Implications for Genome Stability and ...
		chromosomal instability in the presence of cell cycle checkpoints.
		The role of Alu repeat clusters as mediators of recurrent chromosomal aberrations in tumors.
		Expression of recessive alleles by chromosomal mechanisms in retinoblastoma.
	cancerres.aacrjournals.org /cgi/content/full/65/10/4117 (5051 words)

	sacB-5-Fluoroorotic Acid-pyrE-Based Bidirectional Selection for Integration of Unmarked Alleles into the Chromosome of ...
		Digestion of the wild-type chromosomal DNA with EcoRI generated a 2.6-kb fragment containing the 3' half of pyrC, all of pyrE, and the 5' half of dnaB, as indicated.
		20 kb) in the wild-type lane corresponds to the chromosomal pyrE locus.
		(B) The chromosomal helC region was PCR amplified by using the helC2 and helC3 primers and the chromosomal DNA isolated from the individual strains as a template.
	aem.asm.org /cgi/content/full/71/6/3014 (5218 words)

	Vertices Wint95: Genetic Algorithms (Site not responding. Last check: 2007-10-11)
		Each string of ones and zeros is called a chromosome; the chromosome of a given critter is the only source for all the information about the corresponding solution.
		In biological terms, the chromosomal string is the genotype and the solution it represents the phenotype of a particular critter.
		One crossover thus creates two new individuals, called offspring: one containing the beginning portion of the first individual followed by the ending portion of the second individual, and another containing the beginning portion of the second individual followed by the ending portion of the first individual (Table 3).
	www.duke.edu /vertices/update/win95/genalg.html (2545 words)

	Junk DNA - Crystalinks
		In molecular biology, "junk" DNA is a collective label for the portions of the DNA sequence of a chromosome or a genome for which no function has yet been identified.
		These chromosomal regions could be composed of the now-defunct remains of ancient genes, known as pseudogenes, which were once functional copies of genes but have since lost their protein-coding ability (and, presumably, their biological function).
		For example, a high proportion of nonfunctional sequence makes it unlikely that a functional element will be destroyed in a chromosomal crossover event, possibly making a species more tolerant to this important mechanism of genetic recombination.
	www.crystalinks.com /junkdna.html (1268 words)

	Mitotic recombination map of 13cen-13q14 derived from an investigation of loss of heterozygosity in retinoblastomas -- ...
		In cases with a single crossover, informative markers proximal to the box maintained heterozygosity in the corresponding tumor, whereas informative markers distal to the box were homozygous in tumors.
		The data are derived from 42 recombination events detected in the 34 recombination cases (30 with a single detected crossover event and four with three crossovers each).
		The lower boundary of each range is the minimum number of crossovers that definitely occurred between the most proximal marker (AFMz060yc1) and that locus, and the upper boundary is the maximum cumulative number of crossovers that might have occurred.
	www.pnas.org /cgi/content/full/96/6/2952 (4662 words)

	The Chromosomal Basis of Inheritance
		Chromosomes and genes are both paired in diploid cells
		Crossover data is used to construct a map:
		All the chromosomes are re-coded according to the sex of the individual in which they now reside
	www.angelfire.com /scifi/classroom/biology/chromosomalinherit.htm (2789 words)

	Chromosomal arm replacement generates a high level of intraspecific polymorphism in the terminal inverted repeats of ...
		Chromosomal arm replacement generates a high level of intraspecific polymorphism in the terminal inverted repeats of the linear chromosomal DNA of Streptomyces ambofaciens -- Fischer et al.
		Chromosomal arm replacement generates a high level of intraspecific polymorphism in the terminal inverted repeats of the linear chromosomal DNA of Streptomyces ambofaciens
		The chromosomal DNA of the bacteria Streptomyces ambofaciens DSM40697 is an 8-Mb linear molecule that ends in terminal inverted
	www.pnas.org /cgi/content/abstract/95/24/14296 (587 words)

	Human and mouse homologs of Schizosaccharomyces pombe rad1+ and Saccharomyces cerevisiae RAD17: linkage to checkpoint ...
		foci on the chromosomes of mouse spermatocytes undergoing meiotic
		The chromosomal crossover and heteroduplex DNA are indicted.
		There are ~300 foci in this late zygotene nucleus and it is evident that the foci are associated with both unpaired chromosomes and chromosomes that are fully synapsed.
	www.genesdev.org /cgi/content/full/12/16/2560 (7077 words)

	Genetic Analysis of Inherited Hypertension in the Rat -- Rapp 80 (1): 135 -- Physiological Reviews
		A single pair of chromosomes is shown which have replicated into 2 sister chromatids that are still joined at centromere during synapse.
		One pair of SHR chromosomes is represented by open bars, and homologous pair of BN chromosomes is represented by solid bars.
		Thick line represents a chromosome from donor normotensive strain, and thin line represents a chromosome from recipient hypertensive strain [assumed to be Dahl salt-sensitive (S) rats].
	physrev.physiology.org /cgi/content/full/80/1/135 (10257 words)

	mazF, a novel counter-selectable marker for unmarked chromosomal manipulation in Bacillus subtilis -- Zhang et al. 34 ...
		marker in the chromosome, and are therefore eliminated in the
		All of the DNA sequences located between the amyE-front and amyE-back or the bpr-front and bpr-back allow integration into the chromosome of B.subtilis via a double-crossover event, resulting in selection for spectinomycin-resistance.
		Plasmids or B.subtilis chromosomal DNA were used as the template, and the amplified fragments were analyzed by agarose gel electrophoresis.
	nar.oxfordjournals.org /cgi/content/full/34/9/e71 (3922 words)

	INNO: X-RAY (TV) RADIATION - NO FIRM LEVELS! (? Danger at all levels?) RADIATION ...
		Whenever a cell needs to express the genetic information encoded in its nDNA the required chromosomal region is unravelled, genes located therein are expressed, and then the region is condensed back to its quiescent conformation.
		When only one of the two strands of a chromosome has a defect, the other strand can be used as a template to guide the correction of the damaged strand.
		chromosomal translocations and other types of chromosomal rearrangements.
	www.hi.is /~joner/eaps/radhaz1.htm (2902 words)

	Comparative genome sequencing of Drosophila pseudoobscura: Chromosomal, gene, and cis-element evolution -- Richards et ...
		Chromosomes have been color coded to allow identification of interchromosomal synteny blocks.
		Muller element F is not shown because of the lack of sequence anchoring data on this chromosome.
		A hypothetical chromosome is shown with genes A through N and two repeated sequence motifs (open and fl arrows) in a reverse orientation (top).
	www.genome.org /cgi/content/full/15/1/1 (7905 words)

	The DNA damage checkpoint pathways exert multiple controls on the efficiency and outcome of the repair of a ...
		The 6.7 kb band is indicative of the chromosomal met17-s as shown schematically above the Southern blots (lanes 1 to 8).
		The fractions of crossover and non-crossover events were multiplied by the gap repair efficiency (Table 2) and the data are plotted in comparison to 100 events in wild-type cells.
		crossovers between sister chromatids, in mammalian cells (84).
	nar.oxfordjournals.org /cgi/content/full/32/14/4257 (7430 words)

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