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.
Answer:
The activity of cyclic AMP phosphodiesterase is prevented by caffeine. The caffeine prevents further dissociation of cAMP, which eventually increases the response within the body. The activity of neurotransmitters, that is, of noradrenaline or epinephrine, gets increased due to enhancement in response.
This further enhances the activity of the heart, the rate of muscle contractions, blood pressure that further helps in delivering more oxygen to the brain, and other parts of the body. Thus, the inhibition of the enzyme cyclic AMP phosphodiesterase helps the athletes to prevent the wall.
<span>C. Single events or several causes working together to produce extinction in a short period is referred to as mass extinction.
Example:
</span>Destruction of forests, mountains, and bodies of water to satisfy human needs result to the imbalance of nature which also give rise to global warming.
Animals and plants have lost their habitats. They lost their means to live. They lost their food sources and they suffer and die because of humans irresponsible acts.
hope I helped!!
The heat from hotter object goes to the cooler object. when they reach the same temperature the heat flow will stop.
The correct answer is: stratosphere.
This is because their temperatures are rising instead of decreasing.
There are 4 primary layers of the atmosphere on Earth:
Troposphere (6-20km), the layer that we live in, where the weather occurs. Only nitrogen and oxygen present.
Stratosphere (20-50 km), where the airplanes fly, contains the ozone layer, which absorbs harmful radiation from the sun.
Mesosphere (50-85 km), the coldest region of Earth’s atmosphere (-100 C), protective layer
Thermosphere (80-690), the hottest (1500 C) and the thickest layer which consists of the ionosphere and the exosphere.
