Answer:
the answer is B.)black hole
Explanation:
Answer:
complementary base-pairing rules
Explanation:
DNA is the genetic material of living cells. It is a long chain of double-stranded molecules, in which each strand is complementary to one another i.e. Adenine base is paired with Thymine base while Guanine base pairs with Cytosine base following the complementary base pairing rule as proposed by Chargaff. This pairing is responsible for the double helical structure of the DNA.
The complementary base pairs that a DNA molecule contains make it able to produce identical copies of itself during replication or duplication. Before replication of DNA can occur, the double strands need to unwind to form two separate strands, which serves as a template for the synthesis of new complementary strands.
In this manner, each new strand contains one template strand and one complementary strand, which forms two new double helix that is identical to the original strand. This two identical copies of DNA gets separated into two daughter cells, which is the essence of the DNA replication.
In the presence of an enzyme, the Activation energy is lowered. thus the reactions reaches the activation energy and the reaction is initiated faster and therefore completes faster than the reactions without enzymes. Enzymes lower activation energy, which allows a reaction to occur at a faster rate.
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Star is a brilliantly glowing sphere of hot gas whose energyis produced by an internalnuclear fusion process. Stars are contained in galaxies. A galaxy contains not only stars, but clouds of gas and dust. These clouds are callednebulae, and it is in a nebula where stars are born. In the nebula is hydrogen gas which is pulled together by gravityand starts to spin faster. Over millions of years, more hydrogen gas is pulled into the spinning cloud. The collisions which occur between the hydrogen atoms starts to heat the gas in the cloud. Once the temperature reaches 15,000,000 degrees Celsius, nuclear fusion takes place in the center, or core, of the cloud. The tremendous heat given off by the nuclear fusion process causes the gas to glow creating a protostar. This is the first step in the evolution of a star. The glowing protostar continues to accumulate mass. The amount of mass it can accumulate is determined by the amount ofmatter available in the nebula. Once its mass is stabilized, the star is known as a main sequence star. The new star will continue to glow for millions or even billions of years. As it glows, hydrogen is converted into helium in the core by nuclear fusion. The core starts to become unstable and it starts to contract. The outer shell of the star, which is still mostly hydrogen, starts to expand. As it expands, it cools and starts to glow red. The star has now reached the red giant phase. It is red because it is cooler than the protostar phase and it is a giant because the outer shell has expanded outward. All stars evolve the same way up to the red giant phase. The amount of mass a star has determines which of the following life cycle paths the star will take.
