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Chromatid pairs are normally genetically identical, and said to be homozygous. However, if mutations occur, they will present slight differences, in which case they are heterozygous . The pairing of chromatids should not be confused with the ploidy of an organism, which is the number of homologous versions of a chromosome.
Chromosome segregation is the process in eukaryotes by which two sister chromatids formed as a consequence of DNA replication, or paired homologous chromosomes, separate from each other and migrate to opposite poles of the nucleus.
The solenoid structure's most obvious function is to help package the DNA so that it is small enough to fit into the nucleus. This is a big task as the nucleus of a mammalian cell has a diameter of approximately 6 μm, whilst the DNA in one human cell would stretch to just over 2 metres long if it were unwound. [6]
A bivalent. In cellular biology, a bivalent is one pair of chromosomes (homologous chromosomes) in a tetrad.A tetrad is the association of a pair of homologous chromosomes (4 sister chromatids) physically held together by at least one DNA crossover.
Parts of a typical chromosome: (1) Chromatid (2) Centromere (3) Short (p) arm (4) Long (q) arm. In genetics, a locus (pl.: loci) is a specific, fixed position on a chromosome where a particular gene or genetic marker is located. [1]
Crossing over occurs between prophase I and metaphase I and is the process where two homologous non-sister chromatids pair up with each other and exchange different segments of genetic material to form two recombinant chromosome sister chromatids. It can also happen during mitotic division, [1] which may result in loss of heterozygosity.
A sister chromatid refers to the identical copies formed by the DNA replication of a chromosome, with both copies joined together by a common centromere. In other words, a sister chromatid may also be said to be 'one-half' of the duplicated chromosome. A pair of sister chromatids is called a dyad.
Each chromatid has its own kinetochore, which face in opposite directions and attach to opposite poles of the mitotic spindle apparatus. Following the transition from metaphase to anaphase , the sister chromatids separate from each other, and the individual kinetochores on each chromatid drive their movement to the spindle poles that will ...