4. Eukaryotic DNA  is found as chromatin in the nucleus. Concisely describe what is the effect of replacing lysine and arginine in the highly conserved regions of histones with phenyl anime and tyrosine on DNA condensation.

The human genome encodes over 20,000 genes each of the 23 pairs of human chromosomes encodes thousands of genes. The DNA in the nucleus is precisely wound, folded, and compacted into chromosomes so that it will fit into the nucleus. It is also organized so that specific segments can be accessed as needed by a specific cell type

The first level of organization, or packing, is the winding of DNA strands around histone proteins. Histones package and order DNA into structural units called nucleosome complexes, which can control the access of proteins to the DNA regions. Under the electron microscope, this winding of DNA around histone proteins to form nucleosomes looks like small beads on a string. These beads (histone proteins can move along the string (DNA) and change the structure of the molecule

Symbiotic association means one of the organisms, called endosymbiont, is present inside the cells of its host. The most typical examples are endosymbiosis theory of mitochondria and chloroplasts which, according to some theories, are cellular organelles of bacterial origin.
But these theories are still discussed because there are in fact arguments that support endosymbiosis theory and also arguments that disapprove it.

Here are the answer for the exercise explaining the endosymbiosis
A ==> oxygen-using procaryote (before being a mitochondrion)
B ==> mitochondrion
C ==> Nucleus
D ==> endoplasmic reticulum
E ==> Host cell: ancestor of all eucaryotes
F ==> photosynthetic procaryote (before being a chloroplast)
G ==> chloroplast
H ==> Host cell: Ancestor for photosynthetic eucaryotes