U18A1 Distinction.docx - Transcription This is the first step of gene expression this process creates a copy of DNA This copy is known as RNA there are

U18A1 Distinction.docx - Transcription This is the first...

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Transcription This is the first step of gene expression; this process creates a copy of DNA. This copy is known as RNA, there are a few differences between DNA and RNA such as: The Thymines in DNA is replaced with Uracils instead as they require less cellular energy to produce. The sugar in RNA is called. Ribose whereas in DNA it is Deoxyribose, also RNA is a single stranded structure compared to DNA. Initiation- At the start of a gene sequence, certain transcription factors will bind. These transcriptions bind to the promoter site also called the TATA box: 5’--TTGACA-------- TATA AT-------A-------- GENE ----------3’ -35 -10 The TATA box has 25-30 base pairs from the start site of transcription, it is the landing strip for RNA Polymerase. The 5 subunits in the enzyme RNA polymerase combine around the TATA box in several stages to form a (PIC) pre-initiation complex. Elongation- The elongation of the copied strand of RNA. RNA Polymerase directs the binding ribonucleotides to the growing RNA strand in a 5’ to 3’ direction. Each ribonucleotide is placed into the elongating RNA strand whilst joining up to their base pair. This procedure is done until the RNA strand has reached the desired length. After the formation of the PIC, the RNA polymerase is released from other transcription factors, and elongation therefore continues in the 5’ to 3’ direction. The genes are continuously packaged and compacted with chromatin; DNA is tightly packed around histones. The machinery
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