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Topic: Homologous chromosome

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	ABNORMALITIES IN CHROMOSOME STRUCTURE
		Individuals and families have been described with a translocation chromosome abnormality and a concurrent genetic condition; the genetic condition occurring because the chromosome breakpoint is in the midst of a gene.
		Crossovers, or the exchange of chromatids (a normal event in meiosis between homologous chromosomes), that occur within the inversion loop result in gametes with both deletions and duplications that are often not compatible with life and result in a high incidence of miscarriages.
		In contradistinction, a numerical chromosome abnormality in a child is presumed to be due to a sporadic cell division error and parental chromosome studies are not indicated.
	www.usd.edu /med/som/genetics/curriculum/1ECHROM3.htm (1824 words)

	Botany online: Classic Genetics - Chromosomes - The Chromosome Theory - Chromosomal Mutations
		A duplication is the doubling of one or several chromosomal fragments.
		A translocation is the transfer of a chromosomal segment onto a non-homologous chromosome.
		The result is that the chromosomes of the original maternal set stay together in one daughter cell and those of the paternal in the other.
	www.biologie.uni-hamburg.de /b-online/e11/11d.htm (1157 words)

	Homologous chromosome - Wikipedia, the free encyclopedia
		The definition of homologous chromosomes is difficult, and all commonly used definitions have problems.
		Homology of chromosomes is different than homology of genetic sequences, and predates that use of the term homology.
		Homologous chromosomes is also very similar to, and often confused with the term synteny (or gene homology)—which refers to genes located on the same chromosome.
	en.wikipedia.org /wiki/Homologous_chromosome (483 words)

	Concepts of Biology
		These chromosomes are the same size, shape, and carry the same genes (genetic instructions) though the actual expression of the genes may vary.
		The paired chromosomes, called a tetrad, align along the cell equator during metaphase I. The homologous pairs are then separated during anaphase I, which is followed by telophase I. Note that the function of the first meiotic division is to separate the homologous chromosomes.
		Nondisjunction is the failure of chromosomes to properly segregate during meiosis (or mitosis) It is responsible for unusual combinations of chromosomes.
	employees.csbsju.edu /ssaupe/biol115/meiosis.htm (1951 words)

	Homology (biology) - Wikipedia, the free encyclopedia
		Homologous sequences are orthologous if they were separated by a speciation event: if a gene exists in a species, and that species diverges into two species, then the divergent copies of this gene in the resulting species are orthologous.
		Homologous sequences are paralogous if they were separated by a gene duplication event: if a gene in an organism is duplicated to occupy two different positions in the same genome, then the two copies are paralogous.
		Except for the sex chromosomes, homologous chromosomes share significant sequence similarity across their entire length, typically contain the same sequence of genes, and pair up to allow for proper disjunction during meiosis.
	en.wikipedia.org /wiki/Homology_(biology) (972 words)

	Biology 2402 Lecture Notes - Meiosis
		One member of each homologous pair is inherited from either the male or female parent; one member of each homologous pair is placed in each sperm or egg.
		Sister chromatids separate to form daughter chromosomes in anaphase of mitosis; homologous chromosomes separate in anaphase I of meiosis.
		In mitosis the two daughter cells have the same chromosome number as the parent cell; in meiosis the four daughter cells are haploid.
	www.ualr.edu /botany/meiosis.html (1100 words)

	week6Spr'06
		Men a nonhomologous pair of sex chromosomes: one X chromosome that they always inherit from their mom and one small "male" chromosome called Y that they always inherit from dad.
		When solving classical genetics problems for traits on autosomal chromosomes (chromosome pairs #1-22), a single letter abbreviation, upper and lower case is used to stand for the two alleles on the homologous chromosome pair.
		The Y chromosome has only ~200 genes most of which are specific for determining the anatomy and physiology of a boy.
	faculty.valencia.cc.fl.us /emason/week6spr'06.html (987 words)

	AGRY 320 Assignment #1
		The purpose of mitosis is to replicate and partition chromosomes in somatic cells.
		Crossing-over can occur due to the arrangement of homologous chromosomes along the spindle equator at metaphase in meiosis I. The homologous chromosomes are lined up on top of each other, which allows for physical contact between DNA that is similar but not identical in content.
		One chromatid that is paired with the chromatid of the homologous chomosome.
	www.agry.purdue.edu /courses/agry320/pretest_key.htm (1427 words)

	Birgid Schlindwein's Hypermedia Glossary Of Genetic Terms - Search results (Site not responding. Last check: 2007-11-03)
		In prokaryotes, chromosomal DNA is circular, and the entire genome is carried on one chromosome.
		Eukaryotic genomes consist of a number of chromosomes whose DNA is associated with different kinds of proteins.
		The sex chromosomes comprise the 23rd chromosome pair in a human karyotype.
	hal.weihenstephan.de /genglos/asp/genreq.asp?nr=110 (256 words)

	BioMed Central \| Full text \| AtMND1is required for homologous pairing during meiosis in Arabidopsis
		FISH analysis using a centromere 1 specific probe indicated that homologous pairing did not take place in the mutant during zygotene and homologous chromosomes remained apart throughout meiotic prophase and meiosis I. The meiotic phenotype of Atmnd1 is similar to that caused by a mutation in AHP2 which encodes the Arabidopsis orthologue of HOP2 [38].
		Meiotic chromosome spreads were prepared, analyzed, and staged based on chromosomal morphology and with respect to the stage of the surrounding tapetal cells, according to Ross et al., 1996 [33] with minor modifications as described in [52].
		Chromosomes were stained with DAPI (1 μg/ml) and observed on a Zeiss Axioplan 2 Imaging microscope using a 365 nm excitation and 420 nm long pass emission filter and a 100× oil objective.
	www.biomedcentral.com /1471-2199/7/24 (5550 words)

	Double Strand Break-Induced Replication, BIR
		Such a situation prevails in a haploid or hemizygous chromosomes in the G1 stage of the cell cycle, or in special situations such as when a cell lacks the telomerase enzyme that maintains chromosome termini.
		First, when HO endonuclease is used to cleave off the end of one chromosome in a haploid, repair can occur by creating a non-reciprocal translocation, in which a 70 bp sequence centromere-proximal to an HO-induced DSB appears to invade a homologous sequence located on the other chromosome arm, 30 kb from its telomere.
		BIR has also been documented in a diploid experiencing a single HO endonuclease-induced DSB on one chromosome, where repair by gene conversion using a homologous chromosome as a template was prevented by a rad51 mutation.
	www.bio.brandeis.edu /haberlab/jehsite/bir.html (522 words)

	Chromosome Pairing Does Not Contribute to Nuclear Architecture in Vegetative Yeast Cells -- Lorenz et al. 2 (5): 856 -- ...
		of homologous chromosomes in the vegetative nuclei of diploid
		Examples of FISH signals in semispread diploid yeast interphase nuclei which were used to determine the relative positions of chromosomal regions by measuring the two homologous (solid lines in panel a) and four homologous (broken lines in panel a) distances (see also reference 50).
		For each nucleus, the two homologous distances and the four nonhomologous distances were averaged and then ranked according to increasing values irrespective of their affiliation to a particular nucleus.
	ec.asm.org /cgi/content/full/2/5/856 (6799 words)

	IUS Biology Faculty Mitosis
		The homologous chromosomes condense and pair during the mitosis stage of the life cycle of all eukaryotes.
		The reason these chromosomes are paired is that half of an organism's chromosomes came from the paternal gamete and the other half came from the maternal gamete.
		Humans acquire a set of 22 chromosomes and one X chromosome from their mother for a total of 23, and a set of 22 chromosomes and one X or Y chromosome from their father to make up the 46 chromosomes.
	homepages.ius.edu /GKIRCHNE/Mitosis.htm (2735 words)

	Homolgous Recombination & Knockout Mouse
		So cells undergoing homologous recombination are grown in antibiotic to select for recombination and gancyclovir to kill any cells that successfully conducted non-homologous recombination.
		This is usually accomplished by using homologous recombination to replace one allele followed by two or more generations of selective breeding until an breeing pair are isolated that have both alleles of the targeted gene inactivaated or knocked out.
		This embryo is from a strain of mice with gray fur.
	www.bio.davidson.edu /courses/genomics/method/homolrecomb.html (1036 words)

	genome.gov \| 2003 Release: Mechanism Preserves Y Chromosome Gene
		All other chromosomes occur in pairs and preserve genetic integrity by exchanging information with matching genes on the homologous chromosome, a process called "crossing over." But the Y chromosome lacks that option, being the only chromosome that is unpaired.
		The extensive use of gene conversion appears to play a role in the ability of the Y chromosome to edit out genetic mistakes and maintain the integrity of the relatively few genes it carries.
		The sequencing work on the Y chromosome was carried out at the Genome Sequencing Center at the Washington University School of Medicine as part of the Human Genome Project, which receives substantial funding from NHGRI.
	www.genome.gov /11007628 (694 words)

	A role for centromere pairing in meiotic chromosome segregation -- Kemp et al. 18 (16): 1946 -- Genes and Development
		the meiotic segregation of the homeologous chromosomes by tetrad
		Bascom-Slack, C.A., Ross, L.O., and Dawson, D.S. Chiasmata, crossovers, and meiotic chromosome segregation.
		Guerra, C.E. and Kaback, D.B. The role of centromere alignment in meiosis I segregation of homologous chromosomes in Saccharomyces cerevisiae.
	www.genesdev.org /cgi/content/full/18/16/1946 (4102 words)

	The Mnd1 Protein Forms a Complex with Hop2 To Promote Homologous Chromosome Pairing and Meiotic Double-Strand Break ...
		homolog pairing are 15 to 25 kbp in length and correspond to
		Chromosomes are incompletely synapsed in the absence of Mnd1.
		Shown is the frequency of pairing for chromosomes III and V, as well as the frequency of nuclei in which both chromosomes III and V are paired.
	mcb.asm.org /cgi/content/full/22/9/3078 (6361 words)

	Human Chromosomal Disorders
		This is a photograph of the 46 human chromosomes in a somatic cell, arrested in metphase.
		When this chromosome is passed on to offspring the result is usually lethal due to missing genes.
		The X chromosome of some people is unusually fragile at one tip - seen "hanging by a thread" under a microscope.
	www.biology.iupui.edu /biocourses/N100/2k2humancsomaldisorders.html (746 words)

	Basic chromosome terminology for mitosis,
		When a chromosome is examined during mitosis or meiosis there is a pinched in region somewhere along the length of the chromosome called the centromere.
		The centromere is a region to which the spindle fibers attach to the chromosome and it is in a characteristic position that is constant for different types of chromosomes.
		Homologous chromosomes have the same general kind of gene along their length but the details of the gene on one chromosome may be slightly different than the corresponding gene on the other chromosome.
	staff.jccc.net /pdecell/celldivision/chromoterm.html (730 words)

	Transient Homologous Chromosome Pairing Marks the Onset of X Inactivation.
		S3) and found that, whereas Xic movement was constrained by homologous interaction, the flanking regions adopted relatively free positions, with each locus showing near-random distributions across time (fig.
		To learn whether the homologous association represented true physical pairing, we carried out "chromosome conformation capture" (3C) (19), whereby two interacting loci can be detected by crosslinking, intermolecular ligation, and polymerase chain reaction.
		Kissing between homologous chromosomes is a feature of normal meiotic recombination, and kissing between non-homologous chromosomes has been found during normal interphase RNAsynthesis (a).
	www.euchromatin.com /NaXu01.htm (2812 words)

	Positive and Negative Roles of Homologous Recombination in the Maintenance of Genome Stability in Saccharomyces ...
		clones arise due to loss of the entire chromosome with the markers (a), and the remaining chromosome may undergo reduplication afterward (b).
		The frequency of aberrant chromosomes is increased in rad51 mutants:
		Similarly, aberrant chromosomes in such clones could arise due to either interchromosomal or intrachromosomal recombination (b and d).
	www.genetics.org /cgi/content/full/164/1/31 (7211 words)

	Evolutionary conservation of chromosome territory arrangements in cell nuclei from higher primates -- Tanabe et al. 99 ...
		The chromatin of individual chromosomes is organized in chromosome territories (CTs) that are essential components of the
		Idiogramatic illustration of G-banded primate chromosomes or chromosomal subregions homolgous to human chromosome 18 (red; Upper) or 19 (green; Lower).
		HSA18-homologous chromosome material is consistently distributed closer to the nuclear border, whereas HSA19-homologous material is distributed toward the nuclear interior.
	www.pnas.org /cgi/content/full/99/7/4424 (4308 words)

	PAG-XIV (W324) Genes Regulating Initiation Of Meiosis And Homologous Chromosome Pairing In Maize And Arabidopsis. (Site not responding. Last check: 2007-11-03)
		PAG-XIV (W324) Genes Regulating Initiation Of Meiosis And Homologous Chromosome Pairing In Maize And Arabidopsis.
		Genes Regulating Initiation Of Meiosis And Homologous Chromosome Pairing In Maize And Arabidopsis.
		am1 is required for the establishment of meiotic chromosome structure and sister-chromatid cohesion, homologous chromosome pairing, and meiotic recombination.
	www.intl-pag.org /14/abstracts/PAG14_W324.html (287 words)

	Homologous chromosome - definition from Biology-Online.org
		(Science: genetics) a pair of chromosomes containing the same linear gene sequences, each derived from one parent.
		The chromosomes tend to pair or synapse during meiosis.
		This page was last modified 23:11, 20 December 2006.
	www.biology-online.org /dictionary/Homologous_chromosome (106 words)

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