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.
According to the starling law, parasympathetic effects on cardiac rate and contractility include decreasing the rate of contraction and increasing the filling time resulting in a stronger contraction.
The Frank-starling law of the heart states that the stroke volume of the heart increases in response to an increase in the volume of blood filling the heart when all other factors remain constant.
As water molecules from plant leaves evaporate, they attract the water molecules that are still present in the plant, aiding in the movement of water from the roots up through the stems. The water in a plant is transported from the bottom to the top by the combined effects of transpiration and capillary action.
- Water molecules ascend up the cellulose tubes from the roots to the leaves because they tend to cling together (cohesion) and stick to the walls of tubes (adhesion). The water from the leaves then evaporates, aiding in the root system's ability to absorb additional water. We call this mechanism capillary action.
- Water and minerals travel upward from the roots through the xylem due to a negative water potential gradient created by the evaporation of mesophyll cells in the leaves. Small perforations between vessel elements must be made to reduce gas bubbles in the xylem since they can obstruct water flow in the plant.
Learn more about Xylem here:
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Matter: Gases,plasma,melting &freezing, solids, vapor
Not Matter: time,sound,sunlight,heat,gravity
If you have a distension of the stomach that can mean one 4 or more things. you ate something bad or old. you spun around in circles and feel like throwing up. you get a headache and you feel sick from your stomach. you got a stomachache
