Crossing Over and Genetic Recombination in Meiosis
Crossing over occurs between equivalent portions of two nonsister chromatids.
Link to an illustrated discussion of crossing over examined at the level of a cell undergoing meiosis.
crossing over
the exchange of genetic material between members of a homologous chromosome pair
Source: Jenkins, John B. 1990. Human Genetics, 2nd Edition. New York: Harper & Row ...
Crossing Over
Crossing over is the swapping of genetic material that occurs in the germ line.
Crossing Over
During meiosis, when homologous chromosomes are paired together, there are points along the chromosomes that make contact with the other pair.
Non-reciprocal crossing over caused by mismatching of homologous chromosomes. Usually occurs in regions of repetitive DNA.
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crossing over: Where a section of one chromosome switches places with the same section from the other chromosome of the pair. This sometimes occurs when a germ cell makes copies of its chromosomes before dividing.
Crossing over A process that occurs during meiosis in which chromosome partners, one inherited from each parent, physically swap sections with one another. This creates hybrid chromosomes that are a patchwork of the original pair.
crossing over
the reciprocal exchange of genetic material between non-sister chromatids during synapsis of meiosis I.
Crustacea
class in the phylum Arthropoda. Most members of this class are aquatic, although a few are terrestrial.
Unequal crossing over A crossover in which the chromosomal segments exchanged are not equally sized because the breakpoint has occurred at a different place on each homologue.
Crossing over
The term coined by Morgan and Cattell (1912) for the occurrence of new combinations of linked characters.
Crossing over is more likely to occur between genes that are far apart. The farther apart genes are, the greater the probability that crossing over will occur between them.
In the example above, we had 8% crossing over.
Crossing over was first described, in theory, by Thomas Hunt Morgan. The physical basis of crossing over was first demonstrated by Harriet Creighton and Barbara McClintock in 1931.[1]
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This crossing over is an exchange of genes. The genes are mixed up, not resulting in a perfect duplicate like mitosis. The cell divides, leaving two new cells with a pair of chromosomes each.
The exchange of DNA fragments between two DNA molecules or chromatids of paired chromosomes (during crossing over) at the site of identical nucleotide sequences. Homozygote.
One centimorgan is equal to a 1% chance that a marker at one genetic locus will be separated from a marker at a second locus due to crossing over in a single generation.
After the DNA is replicated in the S phase preceding meiosis, the homologous chromosomes (each composed of two chromatids) pair up in Prophase I and then crossing over, ...
The Supraorbital Artery (a. supraorbitalis) springs from the ophthalmic as that vessel is crossing over the optic nerve.
The frequency at which crossing over occurs between two chromosomal loci; the probability that two loci will become unlinked during meiosis.
Related Terms:
Crossing over ...
They 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.
Early in her career, she was the first to describe crossing over during meiosis in plants. At the peak of her career, she realized that genes were not immobile on the chromosomes, but could move and rearrange themselves with startling consequences.
Problem 4: Genetic evidence for crossing over in male flies
If we mated the F1 female and male flies from the cross obtained in problem 3, ...
Events of Prophase I (save for synapsis and crossing over) are similar to those in Prophase of mitosis: chromatin condenses into chromosomes, the nucleolus dissolves, nuclear membrane is disassembled, and the spindle apparatus forms.
An X-shaped crossing formed by the crossing over of homologous chromosomes during meiosis when genetic material is exchanged.
sexual reproduction, reduction division, crossing over, kinetochore, microtubule
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But having invented SRY the key driver of the evolution of the sex chromosomes was the shutting down of recombination of crossing over between this pair.
Recombination frequency. The frequency at which crossing over occurs between two chromosomal loci--the probability that two loci will become unlinked during meiosis.
Homologous recombination: Rearrangement of related DNA sequences on a different molecule by crossing over in a region of identical sequence.
where pairs of homologous chromatids remain in contact during late prophase to anaphase of the first meiotic division. The chiasma indicates where an exchange of homologous segments has taken place between nonsister chromatids by crossing over.
This process is the molecular basis of crossing over during meiosis and some DNA repair mechanisms. Another form of recombination, site-specific recombination, is found where transfer, rearrangement or insertion of specific sections of DNA occurs e.
 See also: Crossing, Chromosome, Chromosomes, Meiosis, DNA
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