Upper arm muscle strain: Introduction. Upper arm muscle strain: Damage to the upper arm muscle due to over-stretching of the muscle tissue. The damage involves tearing the muscle tissue. Small blood vessels may also be damaged which can cause bruising. The symptoms may vary from mild to severe depending on the severity of the damage.
In prophase of mitosis, specialized regions on centromeres called kinetochores attach chromosomes to spindle fibers. The centromere (centro- + -mere) is the part of a chromosome that links sister chromatids. During mitosis, spindle fibers attach to the centromere via the kinetochore.Centromeres were first defined as genetic loci that direhromosomes.hese are X-shaped chromosomes, with the centromere in the middle so that the two arms of the chromosomes are almost equal. A chromosome is metacentric if its two arms are roughly equal in length. In a normal human karyotype, two chromosomes are considered metacentric: chromosomes 1 and 3.
Centromeres help to keep chromosomes properly aligned during the complex process of cell division. As chromosomes are copied in preparation for production of a new cell, the centromere serves as an attachment site for the two halves of each replicated chromosome, known as sister chromatids. Top of page.