The diagram shows part of a pre-mRNA molecule. A G part X (a) (i) Name the two substances that make up part X. (ii) Give the sequence of bases on the DNA strand from which this pre-mRNA has been...

Extracted text: The diagram shows part of a pre-mRNA molecule. A G part X (a) (i) Name the two substances that make up part X. (ii) Give the sequence of bases on the DNA strand from which this pre-mRNA has been transcribed. (b) (i) Give one way in which the structure of an MRNA molecule is different from the structure of a tRNA molecule. (ii) Explain the difference between pre-mRNA and mRNA. (c) The table shows the percentage of different bases in two pre-mRNA molecules. The molecules were transcribed from the DNA in different parts of a chromosome. Part of Percentage of base chromosome A G U Middle 38 20 24 End 31 22 26