0845 numbers, for example, are free to call for up to an hour, during the inclusive minutes of your call package if you're a BT customer. Yet call an 0844 number and you'll be charged up to 5.1p/minute, plus a connection fee of up to 15p.
The resulting mRNA is a single-stranded copy of the gene, which next must be translated into a protein molecule. During translation, which is the second major step in gene expression, the mRNA is read according to the genetic code, which relates the DNA sequence to the amino acid sequence in proteins (Figure 2).
How DNA Encodes for Proteins: 1. Transcription: DNA to mRNA. During transcription, DNA is converted to messenger RNA (mRNA) by an enzyme called RNA polymerase. RNA is a molecule that is chemically similar to DNA, and also contains repeating nucleotide subunits. However, the âbasesâ of RNA differ from those of DNA in that thymine (T) is replaced by uracil (U) in RNA. DNA and RNA bases are also held together by chemical bonds and have specific base pairing rules. In DNA/RNA base pairing, adenine (A) pairs with uracil (U), and cytosine (C) pairs with guanine (G). The conversion of DNA to mRNA occurs when an RNA polymerase makes a complementary mRNA copy of a DNA âtemplateâ sequence. Once the mRNA molecule has been synthesized, specific chemical modifications must be made that enable the mRNA to be translated into protein. 2. Translation: mRNA to protein During translation, mRNA is converted to protein. A group of three mRNA nucleotides encodes for a specific amino acid and is called a codon.