In Human Cells, the Alpha Satellite DNA Repeats …

Question

In human cells, the alpha satellite DNA repeats …
A) have a specific sequence indispensable for the seeding event that leads to chromatin formation.
B) can be seen to be packaged into alternating blocks of chromatin, one of which contains the histone H3 variant CENP-A.
C) are sufficient to direct centromere formation.
D) are necessary for centromere formation.
E) All of the above.

Accepted Answer

Human alpha satellite DNA has been observed to be organized in an alternating pattern, implying a folding scheme that positions the CENP-A-containing nucleosomes in proximity to the proteins of the outer kinetochore. Even though it enhances the seeding step in de novo centromere formation, the alpha satellite DNA is neither necessary nor sufficient for centromere formation: centromeres can form on a DNA molecule that lacks these repeats altogether; furthermore, the same repeat sequences are also found at non-centromeric chromosomal regions.