The correct answers are:
- Methylation of histone tails in chromatin can promote condensation of the chromatin.
- DNA is not transcribed when chromatin is packaged tightly in a condensed form.
- Acetylation of histone tails is a reversible process.
- Some forms of chromatin modification can be passed on to future generations of cells.
- Acetylation of histone tails in chromatin allows access to DNA for transcription.
Histone modifications are post-translational modifications of histone protein that can affect gene expression by altering chromatin structure or recruiting histone modifiers.The most common modifications are methylation, phosphorylation, acetylation and ubiquitylation. All of them affect the binding affinity between histones and DNA and thus loosening (gene activation) or tightening (gene repression) the condensed DNA.
Histone methylation is a transfer of methyl group by histone methyltransferases to lysine or arginine amino acid of protein. Effect of methylation depends on the type of protein that is modified. Demethylation is the reverse process.
Histone acetylation is the process of adding of an acetyl group(by histone acetyltransferases) to histone proteins and it can also activate or inhibit the gene expression. Deacetilation is reverse process.
The organelle that maintains pressure against the cell wall, so that the plant cell keeps it shape, is
the (a) central vacuole.
Answer:
Because natural selection selects for it. Thus it persists.
Explanation:
You have to understand heterozygote advantage. Basically, it's where heterozygotes have an advantage over homozygotes. In the case of sickle cell disease, heterozygotes have an advantage, and natural selection favors whatever is advantageous. Thus, because heterozygotes each have one recessive sickle-cell allele, as natural selection favors the heterozygotes, the recessive sickle-cell allele persists and remains in the gene pool.
The correct answer for this question would be option A. The one that is considered not a logical pairing <span>of another environmental factor that will possibly affect the bluegill population with how that factor would affect it is the ACID RAIN. The rest are considered as factors that would affect the population of the bluegill. Hope this answer helps.</span>
<h2>Koch's Postulates.</h2>
Explanation:
The next step should be isolate the microorganism from the mice and check if it is identical to the original microbe.
According to Koch's postulates, a microbe can be considered as a causative agent of a disease only after all the following are established:
- The microorganism should be present in all the organism suffering from the disease.
- The isolated microorganism should be grown in pure culture.
- The organism grown in the culture should be reintroduced in the susceptible but healthy host.
- Finally the microorganism must be re-isolated from the experimental host an cultured to see whether it is identical to the original specific microorganism.
