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:
DNA polymerase
Explanation:
DNA polymerase enzyme catalyses the reaction of adding nucleotide to growing complementary daughter strand of DNA in the direction of 5' → 3' during elongation in the process of replication. This process requires energy which is taken from nucleotides with three phosphate groups in their backbone similar to ATP (adenine triphosphate)
DNA Replication is when DNA multiplies and make exact copies of itself as part of gene transfer.
Answer: North America
Explanation: About 80 million years ago, North America and Europe, Australia and Antarctica, and India and Madagascar followed suit and separated. Over millions more years, the continents moved to their approximate current positions.
Answer:
A rise in blood carbon dioxide concentration.
Explanation:
The feedback regulation may be defined as the process in which the end product of the metabolic pathway regulates the homeostasis of the body. Two main types of feedback are positive feedback and negative feedback.
The negative feedback mechanism occurs when the end product of the reaction is responsible for the shutdown of the metabolic pathway and decreases its concentration. The breathing is controlled by the negative feedback mechanisms, the increase in carbon dioxide concentration acts as the negative sensor as this sensor is mainly responsible for the increase in amount of oxygen level and maintain homeostasis of the body.
Thus, the correct answer is option (c).
Geiger-Muller tube is instruments requires you test three times the background of the work area.
<u>Explanation</u>:
These detectors are gas filled detectors and hence requires time for responding to the value. This time is taken because during this period it collects the electric charges and features of the electric circuit. It also gets stabilized during this period. This device has thumb rule i.e one must wait or hold for at the least 3 times the time constant before getting the precise and accurate reading. The time constant order is 10 seconds for the ionization chamber but for the Geiger counter it can vary from seconds to greater than 20 seconds
