Jake Kline and Grace Crooke
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.
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.
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.
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.
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.