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  • Topic: DNA, Gene, RNA
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  • Published : December 31, 2012
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3.05 DNA Replication

DNA is the master copy of an organism’s gene. There is also the RNA which copies sections of the DNA molecule and carries the copies outside of the nucleus. DNA and RNA are different in ways. One way is that DNA is double stranded and RNA is single stranded. Another way is that DNA contains thymine and RNA contains nitrogenous base uracil.

Transcription is used to produce complementary mRNA molecule. Transcription uses the enzyme called RNA polymerase. The transcription process occurs inside the nucleus in a eukaryotic cell. First the RNA polymerase joins with a DNA molecule and separates its two strands. One strand of the DNA molecule assembles nucleotides together into a complementary mRNA strand. In the DNA molecules there are sequences called promoters which signal which signal the RNA polymerase and should begin transcribing a section of mRNA. The sequences on the DNA molecule signal that the mRNA molecule is now complete and the transcription stops.

There is something called base pairing. Each base on the DNA molecule has only one base. It will pair with a new mRNA strand. Because RNA contains nitrogenous base uracil (U) and DNA contains thymine, so whenever the DNA strand has adenine (A) the mRNA strand will have uracil (U).

After the transcription process the new mRNA leaves the nucleus it enters the cytoplasm. Then the mRNA is then used in a process called translation. The translation process occurs in the cell’s ribosomes. Each ribosome attaches to a mRNA molecule is the cell’s cytoplasm. Then tRNA molecules bring the amino acid to the ribosome. Every tRNA molecule has a set of three unpaired nitrogenous bases. On the end of the tRNA carries only one type of amino acid. Then tRNA changes the code in the mRNA molecule into a pattern of amino acids. Then the ribosome’s and the rRNA attach the amino acids together , and the protein chain keeps growing until the ribosome stops at the mRNA molecule....
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