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.
Binary fission occurs in single-celled organisms only and mitosis is just one cell dividing into two (eukaroytic cells)
Answer:
- Water entered the potato strips because the potato cells contained higher concentration of solutes than its external environment.
- The solutions are hypotonic to the solution in the potato cells.
Explanation:
According to osmosis, water will move from a region where it is high in concentration to that region where it is low in concentration. However, a region with high solute concentration contains a low water concentration and vice versa.
Hence, according to this question, water is said to move into potato strips from solutions of molar concentrations like 0.0M, 0.2M etc. Water moved into the potato strips because potato cells contained higher concentration of solutes than its external environment. This means that the external solutions are HYPERTONIC i.e. low in solute concentration to the solution in the potato strips.
