Question

Which stages of cell cycle (G1, S, G2, and M) will Chromatin structures such as Nucleosome, chromatosome, 30nm fiber, 300nm coil, 700nm coil, chromatid will be present in the nucleus of a. myoblast, b. macrophage, and c. red blood cell?

Answer 1

a) myoblast

The levels of DNA organization
-primary: sequence of nucleotides, held together by covalent phosphodiester bonds which can become 30 nm fibers,
-secondary: double helix, held together by hydrogen bonds which can become 250 nm fibers,
-tertiary: higher order structures that results from the folding of the double helix - such as nucleosomes, which can become chromatosomes, which can finally become 700 nm chromatid, in which 2 of them are 1400 nm metaphase chromosome.

The next level of tertiary structure after chromatosome-30nm fiber associated of the chromatosomes by linker DNA leads to the making of the 30 nm fibers
-30 nm fibers allows chromatosomes to interact

The next level of tertiary structure after 30 nm fiber is 300 nm loops.

Bae of loop is anchored at chromosome scaffold then the loops are compressed into 250 nm fibers.

DNA during prophase-
when cell reaches prophase,chromosome is compact and heterochromatic all over.
-300 nm chromatids will have thickened to 700nm and the chromosome will be shorter
-there is obviously no dna transcription during mitosis

During metaphase, condensin is separated from DNA during interphase, but enters nucleus at the beginning of M phase and helps fold the 300 nm into the 700nm heterochromatin

300 nm fiber is the natural state during interphase.
-as the cell prepares for mitosis, the 300 nm with the help of condensin becomes 700 nm, and is short and thick
-two of these form the 1400 nm chromosome.

Mature Red blood cells are devoid of nucleus while macrophages are derived from monocyte