It doesn't stay up there for long and there are several different ways that it can get up there. hope this helps:)
Answer:
(C) Aminoacyl-tRNA synthetases have an additional active site that binds to non-cognate tRNAs. The tRNAs that bind to this second active are hydrolyzed and released from the enzyme.
Explanation:
In case of translation, proof reading is done by aminoacyl-tRNA synthetases only. Aminoacyl-tRNA synthetases have two mechanisms to avoid error during translation which are mentioned as under:
<u>(1) Chemical proof reading:</u> Incorrect amino acids rather than being hydrolyzed in catalytic pocket get hydrolyzed in editing pocket and thus they hardly get attached to tRNA.
For example: For distinguishing similar amino acids like isoleucine and valine, isoleucyl-tRNA synthetase uses a second active site which is meant for only valine not for isoleucine. In this particular site, valine which had entered the enzyme is cleaved away with the help of editing reaction after which the enzyme is well prepared to process isoleucine which is the correct amino acid for this enzyme.
<u>(2) Kinetic proof reading: </u>Even if an incorrect amino acid has entered a particular aminoacyl-tRNA synthetase, it does not cause appropriate conformational change in the enzyme because of which the incorrect amino acid loosens from the enzyme and does not get incorporated.
Note: In this example, only chemical proof reading is mentioned not kinetic proof reading.
Answer:
Egg and sperm cells have to have half the number of chromosomes as in body cells so when they combine to form a zygote, the zygote is diploid and has the correct number of chromosomes. This explanation describes why meiosis produces haploid cells.
Explanation:
Meiosis is a type of cell division in which four haploid cells are produced from a diploid parent cell having two copies of each chromosome, where the number of chromosomes in the parent cell is reduced to half by undergoing DNA replication and nuclear division. Diploid cell contains two copies of each chromosome, one inherited from mother and the other from father while haploid cell contains only one copy of each chromosome. Examples of diploid cells (somatic cells) are skin, blood, muscle cells etc. Eggs or ovum (female gametes) and sperm (male gametes) are haploid reproductive cells. If the total number of chromosomes in a diploid cell is represented as '2n', then the number of chromosomes in a haploid cell is 'n'. During the fertilization process in an organism, the correct number of chromosomes is restored when the haploid male and female gamete combined to form a single diploid zygote, which is the first developmental stage of an organism.
Answer:
The correct answer is- photosynthesis
Explanation:
According to the endosymbiotic theory, an ancestral cell engulfed a cyanobacteria and lived in symbiotic association with that bacteria and over time this bacteria evolved into the chloroplast and the ancestral cell developed into plant cell.
So as cyanobacteria was the first aerobic cell that can evolve oxygen and can do photosynthesis to produce organic food so it could be concluded that the presence of endosymbiotic cyanobacteria provided a cell with the advantage of photosynthesis.
