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:
(A) Benthic- Benthic refers to the lowest or the bottom zone of the water body such as seas, and oceans. The organisms existing under such extreme pressure conditions are commonly known as benthic organisms. For example, corals and bivalves.
(B) Pelagic- Pelagic refers to the upper top portion of a water body, covering the open sea areas. The organisms existing in this region include dolphins and sharks.
(C) Sessile- Sessile refers to the property where an organism is stationary and cannot move freely from one place to another. These are known as sessile organisms such as coral polyps, Mussels.
(B) Mobile- refers to the property by which an organism can move freely in any direction it wants. For example, fishes, dolphins.
(E) Evisceration- It is a specific type of property where organisms can eject their internal organs in order to protect themselves from predators. for example, Sea cucumbers.
(F) Chitin- Chitin is a hard shell that is present in various organisms, forming its exoskeleton, for defense purposes. For example, arthropods.
In competition, males use feather color to warn potential rivals that they occupy a piece of territory.
Answer:
Carbon dioxide is a greenhouse gas and traps heat in the atmosphere. Without it and other greenhouse gases, Earth would be a frozen world. But humans have burned so much fuel that there is about 30% more carbon dioxide in the air today than there was about 150 years ago, and Earth is becoming a warmer place.
Answer:
Tree frogs use plants as protection. Golden jackals, once they have been expelled from a pack, will trail a tiger to feed on the remains of its kills. Goby fish live on other sea animals, changing color to blend in with the host, thus gaining protection from predators.
Explanation:
