Answer:
The fawnsfoot is found in the Mississippi drainage and the St. Lawrence
D because the common types of phytoplankton is cyanobacteria,
silica-encased diatoms, dinoflagellates, green algae, and chalk-coated coccolithophores.
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 bald eagle and the black bear are tetrapods, which means that they both have four limbs along with the digits. This shows that they both are the descendants of the four-limbed ancestors. However, the limbs of the bear and the bald eagle have different functions. The forelimbs of both these organisms serves different purpose. Hence, their limbs are homologous organs. The homologous organs are those which have the same ancestry but the functions are different.
