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en.wikipedia.org/wiki/Bivalent_(genetics)

A bivalent, sometimes referred to as a tetrad, is the association of a pair of homologous chromosomes physically held together by at least one DNA crossover. This physical attachment allows for alignment and segregation of the homologous chromosomes in the first meiotic division.

www2.le.ac.uk/projects/vgec/schoolsandcolleges/topics/cellcycle-mitosis-meiosis

The cell copies its chromosomes, but then separates the 23 pairs to ensure that each daughter cell has only one copy of each chromosome. ... It is important that the daughter cells have a copy of every chromosome, so the process involves copying the chromosomes first and then carefully separating the copies to give each ...

courses.lumenlearning.com/biology1/chapter/chromosomal-basis-of-inherited-disorders

In a given species, chromosomes can be identified by their number, size, centromere position, and banding pattern. In a human karyotype, autosomes ... They are caused by nondisjunction, which occurs when pairs of homologous chromosomes or sister chromatids fail to separate during meiosis. Misaligned or incomplete ...

www.britannica.com/science/cell-biology/Cell-division-and-growth

Each pair of chromatids is divided between the two daughter cells during mitosis, or division of the nucleus, a process in which the chromosomes are propelled by attachment to ... The homologous chromosomes are then separated to opposite poles of the meiotic spindle by microtubules similar to those of the mitotic spindle.

www2.palomar.edu/anthro/biobasis/bio_3.htm

When gametes are produced (by meiosis), the paired homologous chromosomes separate so that each gamete contains only one of the pair of alleles for each trait . ... During the first division of meiosis, sections near the ends of chromosomes commonly intertwine and exchange parts of their chromatids with the other ...

www.ncbi.nlm.nih.gov/pmc/articles/PMC2475728

Thus, the distribution of crossovers in S. cerevisiae appears to resemble that found in several higher eukaryotes where the outermost chromosomal regions show ... DURING meiosis pairs of homologous chromosomes replicate, undergo reciprocal recombination (crossing over or chiasma formation), and then segregate ...

www.thoughtco.com/homologous-chromosomes-definition-373469

Apr 13, 2017 ... Sister chromatids pair up forming what is called a tetrad. While in close proximity, homologous chromosomes sometimes exchange sections of DNA. This is known as genetic recombination. Homologous chromosomes separate during the first meiotic division and sister chromatids separate during the ...

www.learner.org/courses/essential/life/session3/closer2.html

In an elegant process called meiosis, each sex cell receives one member of each chromosome pair—23 total. When sperm fertilizes egg, ... The two strands of each chromosome are then separated during the second cell division, still maintaining half the number that existed in the parent cell. This results in four daughter ...

www.sciencedirect.com/science/article/pii/S0092867404009961

Oct 29, 2004 ... The excess number of chromosomes results from chromosome missegregation during meiosis, and the aneuploidy is passed on from the resulting ..... by spindle microtubules, or by nucleating microtubules from the kinetochore, which are then integrated into the existing spindle (Khodjakov et al., 2003).