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:
Mammals
Birds
Explanation:
The Organs which perform same function and looks but they are different in their structure from each other are called as analogous organs.
Organs are the structures that made up of two or more tissues organized to carry out a particular function.
An organ or bone that appears in different animals with same function is called homologous structure.
Homologous organs have similar origin n basic structure but perform different functions in different organisms. Analogous organs are different in basic structure but perform same functions.
Different animals have bones that appear very similar in form or function and seem to be related.
Examples
The arm of a human, the wing of a bird or a bat, the leg of a dog and the flipper of a dolphin or whale are homologous structures. They are different and have a different purpose, but they are similar sharing common traits.
The forelimbs of all mammals have the same basic bone structure.The structures are similar because they evolved to do the same job. For example, the wings of bats and birds.
Explanation:
The answer is A.
When the body temperature returns to normal,the respiratory system sends a message to the skeletal system to stop shivering.
Answer:
Sediment in rivers gets deposited as the river slows down. Larger, heavier particles like pebbles and sand are deposited first, whilst the lighter silt and clay only settle if the water is almost still.
Dead zones are low-oxygen<span>, or hypoxic, areas in the world's oceans and lakes
(answer is dead zones)</span>
