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DNA sequences are both necessary and sufficient to specify centromere identity and function in organisms with point centromeres. In budding yeasts, the centromere region is relatively small (about 125 bp DNA) and contains two highly conserved DNA sequences that serve as binding sites for essential kinetochore proteins. [26]
Role of the centrosome in cell cycle progression. Centrosomes are associated with the nuclear membrane during the prophase stage of the cell cycle. During mitosis, the nuclear membrane breaks down, and the centrosome-nucleated microtubules can interact with the chromosomes to build the mitotic spindle.
The sister chromatids will be distributed to each daughter cell at the end of the cell division. Whereas if the chromosome is isobrachial (centromere at centre and arms of equal length), the p and q system is meaningless. At either end of a chromosome is a telomere, a cap of DNA that protects the rest of the chromosome from damage.
Centromere protein A, also known as CENPA, is a protein which in humans is encoded by the CENPA gene. [5] CENPA is a histone H3 variant which is the critical factor determining the kinetochore position(s) on each chromosome [ 6 ] in most eukaryotes including humans.
However, the emergence of research in neocentromeres troubles this conventional definition and questions the function of a centromere beyond being a “landing pad” for kinetochore formation. [4] This expands the scope of the centromere's function to include regulating the function of the kinetochore and the mitotic spindle.
Centromere protein B is a highly conserved protein that facilitates centromere formation. It is a DNA -binding protein that is derived from transposases of the pogo DNA transposon family. It contains a helix-loop-helix DNA binding motif at the N-terminus and a dimerization domain at the C-terminus.
centromere A specialized DNA sequence within a chromosome that links a pair of sister chromatids. The primary function of the centromere is to act as the site of assembly for kinetochores, protein complexes which direct the attachment of spindle fibers to the centromere and facilitate segregation of the chromatids during mitosis or meiosis.
The following are some of the gene count estimates of human chromosome 18. Because researchers use different approaches to genome annotation their predictions of the number of genes on each chromosome varies (for technical details, see gene prediction).