Dna Transcription and translation
DNA Replication
Deoxyribonucleic acid (DNA) contains the genetic instructions for the biological development of a cellular form of life including some viruses. DNA is an antiparallel double helix molecule with sugar-phosphate backbone on the outer side and nitrogen bases in the inner side. The bases are paired specifically, also known as complementary pairing, Adenine
(A) with Thymine (T), and Guanine (G) with Cytosine (C) by two and three hydrogen bonds, respectively. DNA is a long polymer of nucleotides (a polynucleotide) that transfers the information to RNA (mRNA) that in turn controls the sequence of amino acid residues in proteins, using the genetic code. James Watson and Francis Crick proposed the DNA double helix structure in 1953 and shared the the Noble Prize in 1962 with Maurice Wilkins.
Models for DNA Replication
While proposing their double helix model, Watson and Crick were particularly excited because the complementary nature of the DNA molecule suggested a self-replicating mechanism, a property which would be crucial for a genetic material. Three hypothesis were in contention regarding the mode of self-replication of DNA and these were (Fig. 1):
i)
Conservative replication according to which the original strand is unchanged and a completely new DNA molecule is synthesized. ii) Semi-conservative replication describes a way in which each DNA strand of a double helical molecule serves as a template for the synthesis of two new DNA molecules each with one new and one old strand. iii) Dispersive replication suggests more-or-less random interspersion of parental and new segments in daughter DNA molecules.
2
In 1957, Matthew Meselson and Franklin Stahl, proved that DNA is replicated by semiconservative mode of replication. Their experiment involved growing a culture of
Escherichia coli in a medium containing 15NH4Cl (ammonium chloride labeled with the heavy isotope of nitrogen) for several generations. A small aliquot of
Deoxyribonucleic acid (DNA) contains the genetic instructions for the biological development of a cellular form of life including some viruses. DNA is an antiparallel double helix molecule with sugar-phosphate backbone on the outer side and nitrogen bases in the inner side. The bases are paired specifically, also known as complementary pairing, Adenine
(A) with Thymine (T), and Guanine (G) with Cytosine (C) by two and three hydrogen bonds, respectively. DNA is a long polymer of nucleotides (a polynucleotide) that transfers the information to RNA (mRNA) that in turn controls the sequence of amino acid residues in proteins, using the genetic code. James Watson and Francis Crick proposed the DNA double helix structure in 1953 and shared the the Noble Prize in 1962 with Maurice Wilkins.
Models for DNA Replication
While proposing their double helix model, Watson and Crick were particularly excited because the complementary nature of the DNA molecule suggested a self-replicating mechanism, a property which would be crucial for a genetic material. Three hypothesis were in contention regarding the mode of self-replication of DNA and these were (Fig. 1):
i)
Conservative replication according to which the original strand is unchanged and a completely new DNA molecule is synthesized. ii) Semi-conservative replication describes a way in which each DNA strand of a double helical molecule serves as a template for the synthesis of two new DNA molecules each with one new and one old strand. iii) Dispersive replication suggests more-or-less random interspersion of parental and new segments in daughter DNA molecules.
2
In 1957, Matthew Meselson and Franklin Stahl, proved that DNA is replicated by semiconservative mode of replication. Their experiment involved growing a culture of
Escherichia coli in a medium containing 15NH4Cl (ammonium chloride labeled with the heavy isotope of nitrogen) for several generations. A small aliquot of