Lexic.us

Definition of Crossing over

1. Noun. The interchange of sections between pairing homologous chromosomes during the prophase of meiosis.

Definition of Crossing over

1. Verb. (present participle of cross over) ¹

¹ Source: wiktionary.com

Medical Definition of Crossing over

1. The breaking during meiosis of one maternal and one paternal chromosome, the reciprocal exchange of corresponding sections of DNA along pairs of homologous chromosomes by symmetrical breakage and crosswise rejoining of the chromosomes. This results in the transfer of a block of genes from each chromosome to its homologue. In contrast to genetic recombination, which is a phenotypic phenomenon, crossing-over is genotypic. Any even number of crossing-overs between two loci will cancel out phenotypically and no recombination will occur. Recombination can result from DNA exchange of alleles between between homologous chromatids in meiosis, giving rise to chiasmata. Compare: recombination. (10 Nov 1998)

Lexicographical Neighbors of Crossing Over

Literary usage of Crossing over

Below you will find example usage of this term as found in modern and/or classical literature:

1. Julius Caesar by William Shakespeare (1912)
"... then follow Calpurnia, Portia, and other women, and other senators following, those from L crossing over. Brutus and Cassius cross, and when Casca, ..."

2. Biological Bulletin by Marine Biological Laboratory (Woods Hole, Mass.) (1912)
"The test showed, in fact, that crossing over had occurred, but the result was obscured, because, necessarily, the Fj flies would still be gray, ..."

3. Science by American Association for the Advancement of Science (1916)
"Not only do the sex- linked factors show no crossing over in the male, but experimental breeding shows that in the male there is no crossing over even of ..."

4. The Physical Basis of Heredity by Thomas Hunt Morgan (1919)
"CHAPTER VIII crossing over AND CHROMOSOMES THERE are several occasions in the maturation period of the germ-cells when it would seem that there might be an ..."

5. The Mechanism of Mendelian Heredity by Thomas Hunt Morgan (1915)
"If we represent the percentages of crossing over as relative distances along the ... If crossing over takes place between white and miniature and between ..."

6. An Introduction to Cytology by Lester Whyland Sharp (1921)
"crossing over as shown in the diagram. Most of the P\ flies show the same combinations as their grandparents, which indicates that no crossing over has ..."

7. The Living Age by Making of America Project, Eliakim Littell, Robert S. Littell (1868)
"They separated, and Monsieur le Cure, crossing over to La Maison Prévost, told Madame Jean, when she opened the door, that it was absolutely necessary he ..."

8. Lawyers' Reports Annotated by Lawyers Co-operative Publishing Company (1905)
"... marked В on the map: another crossing over the spur leading to the Anaconda ore house, marked С on the map; a crossing over the spur leading to the ..."

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