What are Eukaryotic chromosomes made up of?
chromatin, a complex of DNA and associated
proteins
What are Eukaryotic chromosomes sites of?
A significant amount of RNA is also associated with chromosomes, because the chromosome is the site of RNA synthesis within the cell
What is it called when DNA of a chromosome exists as a very long unbroken double stranded fiber?
Duplex
If the eukaryotic nucleus is gently disrupted and the DNA is
examined with an electron microscope, you can see that it resembles a string of beads. What are these beads called and what ar they made up of?
Each
of these “beads” is called a nucleosome. Each nucleosome is composed of a double loop of
DNA coiled around a core of eight histone molecules
What are histones rich in? What is a result of this richness with DNA?
Histone molecules are small, basic
polypeptides, rich in the amino acids arginine and lysine. Because so many of the histone amino acids are basic, these molecules are very positively charged. The DNA duplex is
negatively charged; therefore, DNA is strongly attracted to the histones and wraps tightly
around the histone core of each nucleosome.
What is an example of a histone molecule that acts to stabilize the array?
h1 histone
What are nucleosome units coil into a cylindercal fibers called? How big are they?
Solenoid, 30nm in diameter
What are supercoils?
Further coiling of the DNA occurs when these fibers wrap up into higher-order coils
What are the levels of chromosome packaging from largest to smallest?
What are highly condensed portions of the chromatin called, are they expressed always expressed?
heterochromatin. These areas of the
chromosome may even remain condensed permanently, so that their DNA is never
expressed
What are euchromatin
Regions of the chromosome that are less condensed are called euchromatin,
and are not condensed except during cell division, when the compact packaging that occurs
facilitates the movement of the chromosomes. At all other times, the euchromatin is present
in an open configuration and genes can be transcribed and expressed.
When do sister chromatids form”?
When do chromosomes acquire their distinct shape and size?
What regions are sister chromatids joined together
