【求助】转录起始位点

转录起始位点是不是第一个外显子的第一个碱基？

yes

我觉得不一样，转录起始位点应该在第一个外显子的第一个碱基的上游。

转录起始位点是DNA分子中开始RNA转录的位置，而第一个外显子是经过剪切后留下来的第一个外显子，一般来说，应该在其5’还有一段UTR序列（还是在转录起始位点的下游），因此一般来讲，转录起始位点应该在第一个外显子第一个碱基的上游，也就是其5’端。

In many genes, each exon contains part of the open reading frame (ORF) that codes for a specific portion of the complete protein.

Below is a diagram of a heterogeneous nuclear RNA (hnRNA), which is an unedited mRNA transcript, or pre-mRNAs. Exons can include both sequences that code for amino acids (red) and untranslated sequences (grey). Stretches of unused sequence called introns (blue) are removed, and the exons are joined together to form the final functional mRNA. The notation 5' and 3' refer to the direction of the DNA template in the chromosome and is used to distinguish between the two untranslated regions (grey).

Some of the exons will be wholly or part of the 5' untranslated region (5' UTR) or the 3' untranslated region (3' UTR) of each transcript.

Sorry I did not make it clear. A schematic diagram based on yours is shown below to better explain my point.

tss: transcription start site.

the start of the 5'UTR is the start of 1st exon.

you can check the book "Genes VIII" by Lewin, figure 2.1 (at page 33) and figure 2.7 (at page 37).

below is the link of the book

http://www.scribd.com/doc/29717840/Genes-Viii

You are right on the notion that the 5'UTR is the start of 1st exon. However, you merely focused on the relationship between 5'UTR (NOT TSS) and exon, and therefore did not convince me that TSS is the start of 1st exon (pre-mRNA processing?). I will check this out when　I have free time.

有用,好好看看!!谢谢

谢谢大家了，给我详细的讲解

严重同意woxingwosu的观点！非常有用，学习了！