In: Biology
You engineer a strain of S. cerevisiae cells that express mutant histone octomer complexes that exhibit a negatively-charged DNA-binding surface. Which of the following would you expect to happen in a sample of these cells?
The chromosomes of the mutant strain would condense only during mitosis.
Nucleosome core particles would not form.
Epigenetic inheritance would be observed.
All chromatin in the mutant strain would be condensed.
The DNA would package too tightly for any gene expression to occur.
B. Nucleosome core particles would not form if the histone octamer complexes exhibit negative charge.
The charge of the histone octamer is a very important factor in forming a nucleosome. The DNA is negatively charged and the histone complex will be positively charged. These opposite charges between them enhance DNA binding on the histone by electrostatic interactions. But when both tend to show negative charges as in this case the DNA binding on the complex would not occur and consequently nucleosomes will not form.
Chromosomes will also not form because nucleosomes are not formed at the first place. Nucleosomes are the structural unit of a chromatin which again condenses forming a chromosome. Without a nucleosome there will be no chromosomes in the cell. Linear DNA coiling around histone complexes is an example of epigenetic inheritance, since there are many epigenetic factors that contribute to the formation of a nucleosome. As binding is not favored here, epigenetic inheritance cannot be seen.