DNA Transcription

Jake Kline and Grace Crooke

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Starting DNA Transcription

As shown in the picture above, the RNA Polymerase will beginning in the promoter region, which contains a "TATA Box" which is a constant sequence of Thymine-Adenine bonds. The Polymerase will begin here because there is a weaker bond between Adenine and Thymine, than between Guanine and Cytosine. This process is known as initiation. Transcription takes place in the nucleus.
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Transcription Taking Place

Once the RNA Polymerase has started transcription and reading the template strand of DNA, the RNA being created will be a direct match to the non-template strand. However, in RNA Thymine is replaced with Uracil. This is the process of elongation.
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AAUAAA Sequence

The AAUAAA sequence is known as the "stop sequence" for the RNA Polynerase to stop unzipping and transcripting the DNA 10-35 more nucleotides downstream. This is know when the pre-mRNA will break off and enter through the spliceosome. This process is known as termination.
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RNA Splicing

Introns are the non-coding nucleotides on the pre-mRNA, while extrons are the segments needed for coding to make the protein. With that said, when the pre-mRNA enters the spliceosome, which is made of a variety of proteins, it will cut out the introns and connect the extrons. Once exited the spliceosome, the pre-mRNA is now a mature mRNA ready to leave the nucleus. It can be referred to as alternative splicing because the spliceosome can splice up the pre-mRNA in multiple ways.
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5' Cap and Poly-A Tail

The 5' cap is a modified form of guanine added to help the mRNA leave the nucleus.

The poly-A tail is a cap at the end of 50-250 adenine nucleotides in order to help protect and guide the mRNA on the 3' end.

Sources

https://www.smore.com/5jd2k/edit?ref=show_author


Reece, Jane B., and Neil A. Campbell. Campbell Biology. Boston: Benjamin Cummings / Pearson, 2011