Answer:
The correct answer is - a. DNA primers, and d. DNA polymerase that is heat stable.
Explanation:
In Polymerase chain reaction (PCR) there are many components are required in a overall process but there is two major components that are required for amplification of a specific section of DNA:
a. DNA primers- these are short and strands or sequence of ssDNA, a pair of these sequence acts as the starting site for a new strand which is used to hybridize with the sample DNA and mark the region of the DNA of interest to be amplified.
d. DNA polymerase that is heat stable- PCR technique involves various reaction that are performed at different temperatures. A thermophilic bacteria Thermus aquaticus is used to get this heat stable enzyme, Which lives in hot springs.
Thus, the correct answer is - a. DNA primers, and d. DNA polymerase that is heat stable.
Genetic engineering based on recombination was pioneered in 1973 by American biochemists Stanley N. Cohen and Herbert W. Boyer, who were among the first to cut DNA into fragments, rejoin different fragments, and insert the new genes into E. coli bacteria, which then reproduced.
Hormones are secreted and released into the blood by Endocrine glands.
Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, thyroid gland, parathyroid gland, hypothalamus and adrenal glands.
The food chain that is shown in the food web could be any of the following:
- tree → deer → mountain lion
- grass → rabbit → mountain lion
- grass → rabbit → hawk
- grass → grasshopper → frog → snake → fox
- grass → grasshopper → snake → hawk
- grass → grasshopper → snake → fox → mountain lion
- tree → caterpillar → robin → fox → mountain lion
<h3 /><h3>FURTHER EXPLANATION</h3>
A food chain shows a unidirectional feeding relationship among organisms in an ecosystem. The organisms occupy a certain "place" in the food chain called trophic level. Food chains may have several trophic levels which always begin with the producers.
- Producers are organisms which make their own food. Plants are examples of producers.
- The organisms the directly feed on the plants are called the primary consumers. They are either herbivores or omnivores.
- The organisms that feed on the primary consumers directly are called secondary consumers. Those that feed on the secondary consumers are called tertiary consumers and quaternary consumers feed on tertiary consumers. These are either omnivores or carnivores.
- The apex predator is the animal at the top of the food chain. It is preys on the organisms in the lower trophic levels but nothing preys on it.
A food web, on the other hand, is a series of food chains showing the interdependence of organisms in an ecosystem.
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Keywords: food chain, food web
