Chromosome Structure Flashcards
histones
proteins responsible for the main level of DNA packing in interphase chromatin
how do histones bind to DNA
more than 1/5 of a histone’s amino acids are positively charged, so they bind tightly to negatively charged DNA
diameter of an unfolded chromatin
10 nm
beads on a string
10 nm fiber chromatin resembles this structure; each bead is a nucleosome, and the strings are linking DNA
nucleosome consists of
DNA wound twice around a protein core of 8 histones; two each of the four main types
histone tail
the amino end of each histone extends out from the nucleosome and is involved in the regulation of gene expression
euchromatin
less compacted interphase chromatin
heterochromatin
more compacted chromatin
which type of chromatin is inaccessible to proteins that transcribe genetic information
heterochromatin
chromatin during prophase
condensin II creates a scaffold and condensin I creates loops of 10 nm fibers to make each sister chromatid wider and shorter; half as long
chromatin during prometaphase
condensin I binds to DNA outside the scaffold, making smaller loops from the larger ones; chromosome gets denser, shorter, and wider, and begins to twist into a helix
chromatin during metaphase
the chromosome is at its most dense
virus
an infectious particle consisting of little more than genes packaged in a protein coat
are viruses alive
no; in between life-forms and chemicals
how big are the tiniest viruses
20 nm
