The Role of DNA

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The Role of DNA
The fundamental role of DNA is for replication of the specific information, by coding for the
genetic information for the messenger RNA (mRNA ) via transcription.
The section of DNA that holds the information for one polypeptide chain is called a cistron
or gene
Where the gene is located on the chromosome is called the locus (loci plural).
Homologous chromosomes have the same genes at the same loci
Alleles are different forms of the same gene (i.e. blue and brown are alleles for the eye
colour gene)
The genetic code is the messenger RNA (mRNA) transcribed from a gene
Each of the 20 amino acids used to make a protein is represented by three base pairs
called a codon . There are three stop codons which do not code for an amino acid and
mark the end of a protein chain. Three consecutive bases are called a triplet
Non-overlapping means that each base is only part of the triplet and only specifies one
amino acid
DNA is degenerate . There are more codons that amino acids and therefore some amino
acids have more than one codon
Universal code. The same codon codes for the same amino acids in all organisms (with a
few exceptions)
Structure of RNA
Ribonucleic acid (RNA) is a polymer. Each mononucleotide contains:
The pentose (5 carbon sugar) ribose
Phosphate group
The bases in RNA are:
Messenger RNA

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RNA is complementary to DNA. It is single stranded and arranged into a single helix that can
easily be broken down.
Transfer RNA
tRNA molecules transport specific amino acids to the ribosome during protein synthesis. These are
between 75 and 90 bases in side. tRNA is single stranded and arranged into a clover shape .…read more


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