Answer:
An amino acid activates the repressor so that the repressor binds to the operator and prevents transcription.
Explanation:
In an operon, promoter is followed by operator which is finally followed by the structural genes to be transcribed. RNA Polymerase binds to the promoter and initiates transcription. A repressor can negatively control the transcription process by binding to the operator so that the RNA Polymerase is not able to move forward and transcription is halted.
For example: in trp operon, tryptophan amino acid binds to the repressor molecule which leads to change in repressor's shape. The repressor is now able to bind to the operator and prevent transcription.
Because pioneer species are the first to return after a disturbance, they are the first stage of succession, and their presence increases the diversity in a region. They are usually a hardy plant, algae or moss that can withstand a hostile environment.
Options for the question have not been provided. They are as follows:
(1) DNA in muscle cells
(2) base sequences in liver cells
(3) genes in an egg cell
(4) number of chromosomes in a fetal bone cell
Answer:
(3) genes in an egg cell
Explanation:
Evolution is the change in characteristics of a species which it develops over the time. These changes can be a result of natural selection, genetic drift, founder effect etc. They are passed from one generation to another hence the alleles for them get fixed in the population.
For evolution to occur, change should take place in germ cells. Germ cells are the one which fuse to form the organisms of next generation. If there is a change in their genes, it would also appear in next generation, unlike changes in genes of somatic cells. Since egg cell is a germ cell it is the correct answer.
<span>The cell has 1% concentration of the salt. The external environment is highly concentrated with 25% saline solution. This will lead to release of water outside the cell, by passive diffusion from a region of high conentration of solvent to lower concentration. Thus, the cell will shrink.</span>
