Because the original DNA strands are complementary and run antiparallel, only one new strand can begin at the 3' end of the template DNA and grow continuously as the point of replication.
The other strand must grow in the opposite direction because it is complementary, not identical to the template strand. The result of this side's discontiguous replication is the production of a series of short sections of new DNA called Okazaki fragments.
The sections are joined by the action of an enzyme called DNA ligase which connects the sections together by forming the missing phosphodiester
P adenine P cytosine guanine P P thymine guanine P P 5’ Okazaki Fragments P adenine P cytosine thymine 3’ P thymine P guanine adenine 3’ P thymine P guanine guanine 3’ 5’ P P thymine P guanine guanine 3’ 5’ P
Tools for Manipulating DNA, Restriction Enzymes and Hybridization
A codon is recognized following specific base-pairing of mRNA with a sequence of three bases on a tRNA called the anticodon
Some tRNAs can recognize more than one codon.
In these cases, tRNA molecules form standard base pairs only at the first two positions of the codon, while tolerating irregular base pairing at the third position. This apparent mismatch phenomenon is called wobble .
The Genetic Code The codon AUG specifies the amino acid Methionine which always begins a protein molecule. There is no amino acid associated with the codons UAA, UAG, and UGA. These codons always end a protein molecule. Note: there are 6 codons which specify Leucine and Serine, only a single codon for Methionine and Tryptophan. All the other amino acids have at least 2 codons which specify them. First Letter Middle Letter = U Middle Letter = C Middle Letter = A Middle Letter = G Last Letter U UUU - Phenylalanine UCU - Serine UAU - Tyrosine UGU - Cysteine U U UUC - Phenylalanine UCC - Serine UAC - Tyrosine UGC - Cysteine C U UUA - Leucine UCA - Serine UAA - STOP UGA - STOP A U UUG - Leucine UCG - Serine UAG - STOP UGG - Tryptophan G C CUU - Leucine CCU - Proline CAU - Histidine CGU - Argenine U C CUC - Leucine CCC - Proline CAC - Histidine CGC - Argenine C C CUA - Leucine CCA - Proline CAA - Glutamine CGA - Argenine A C CUG - Leucine CCG - Proline CAG - Glutamine CGG - Argenine G A AUU - Isoleucine ACU - Threonine AAU - Asparagine AGU - Serine U A AUC - Isoleucine ACC - Threonine AAC - Asparagine AGC - Serine C A AUA - Isoleucine ACA - Threonine AAA - Lysine AGA - Argenine A A AUG - Methionine - START ACG - Threonine AAG - Lysine AGG - Argenine G G GUU - Valine GCU - Alanine GAU - Aspartate GGU - Glycine U G GUC - Valine GCC - Alanine GAC - Aspartate GGC - Glycine C G GUA - Valine GCA - Alanine GAA - Glutamine GGA - Glycine A G GUG - Valine GCG - Alanine GAG - Glutamine GGG - Glycine G