DNA and identification

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DNA and Identification.

DNA.

the genetic code is made up of triplet codes of three bases to make up each amino acid. the genetic code is non-overlapping, so each three bases codes for only one amino acid each. It is also degenerate, meaning it contains more information than it needs. Often only the first two nucleotides matter in determining which amino acid results. This means that if the final base in the triplet is changed because of mutation, the same amino acid would still result, and have no effect on the organism, so it is a form of protection against mutation.

Transcription.

1.RNA polymerase attaches to the DNA double-helix at the beginning of a gene. this breaks the hydrogen bonding between the two DNA strands, separating the strands, and the DNA molecule unwinds.

2. one of the strands is used as a template strand to make an mRNA copy. the DNA template strand is called the antisense or template strand.

3. the RNA polymerase lines up free RNA nucleotides alongside the template strand. complementary base pairing means that the mRNA strands end up being a reverse copy of the DNA template.

4. RNA polymerase moves along the DNA, separating the strands and assembling the mRNAstrand. the hydrogen bonds in the DNA reforms once RNA polymerase has passed by, and the double helix reforms.

5. When the RNA polymerase reaches a stop codon, it stops making mRNA and detaches from the DNA.

6. mRNA moves out of the nucleus through a nuclear pore.

Before translation, the mRNA is modified. introns, sections of the DNA which do not code for amino acids are spliced out of the mRNA before the mRNA leaves the nucleus. the exons, which do code for amino acids, can be joined together in different orders to form different mRNA strands, therefore one amino acid sequence can code for more than one protein.

Translation.

1. the mRNA…

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