| chi structure | <molecular biology> The name for the X-shaped structure which forms during the recombination process between two plasmids, or circular pieces, of DNA. The Greek letter chi resembles this structure. (05 Jan 1998) |
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| chi | 1. The 22nd letter of the Greek alphabet, χ. 2. In chemistry, denotes the 22nd in a series. 3. Symbol for the dihedral angle between the alpha-carbon and the side-chains of amino acids in peptides and proteins. (05 Mar 2000) |
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| chi sequence | <molecular biology> A specific sequence of nucleotides on a site on the genome of the bacteria Escherichia coli which strongly encourages recombination and crossing over to occur at that site. (05 Jan 1998) |
| chi-sequences | A specific DNA sequence in bacterial genomes that allows for extensive genetic recombination. (05 Mar 2000) |
| chi site | <molecular biology> Short, active sequences of DNA which strongly encourages crossing over of chromosomes to occur at that site. These sites become chiasmata more often than other sites. (05 Jan 1998) |
| chi-square | A statistical technique whereby variables are categorised to determine whether a distribution of scores is due to chance or experimental factors. (05 Mar 2000) |
| chi squared | <statistics> Common statistical test to determine whether the observed values of a variable are significantly different from those expected on the basis of a null hypothesis. (18 Nov 1997) |
| chi-square distribution | A distribution in which a variable is distributed like the sum of the the squares of any given independent random variable, each of which has a normal distribution with mean of zero and variance of one. The chi-square test is a statistical test based on comparison of a test statistic to a chi-square distribution. The oldest of these tests are used to detect whether two or more population distributions differ from one another. (12 Dec 1998) |
| chi-square test | A statistical method of assessing the significance of a difference, as when the data from two or more samples is represented by a discrete number such as the numbers of females and males attending each of two colleges. Synonym: x2 test. (05 Mar 2000) |
| brush heap structure | Haphazard interlocking of fibrils in a gel or hydrocolloid impression material. (05 Mar 2000) |
| gel structure | Brush heap structure of fibrils giving firmness to hydrocolloids. (05 Mar 2000) |
| genetic fine structure | The study of genes on the level of their nucleotide sequences and what happens to their molecular structure at that level. (09 Oct 1997) |
| group structure | The informal or formal organization of a group of people based on a network of personal relationships which is influenced by the size and composition, etc., of the group. (12 Dec 1998) |
| molecular structure | The location of the atoms, groups or ions relative to one another in a molecule, as well as the number and location of chemical bonds. (12 Dec 1998) |
| cointegrate structure | A structure of DNA produced by the fusion of two replicons, one possessing a transposon. (05 Mar 2000) |
| cruciform structure | A structure, shaped like a cross, which can form during homologous recombination when inverted base-pair repeats pair with each other on the same strand of DNA instead of with homologous sections on a different strand of DNA. (09 Oct 1997) |