2.7 DNA Replication, Transcription and Translation

Essential Idea:

Understandings:

The replication of DNA is semi-conservative and depends on complementary base pairing.
Helicase unwinds the double helix and separates the two strands by breaking hydrogen bonds.
DNA polymerase links nucleotides together to form a new strand, using the pre-existing strand as a template.
Transcription is the synthesis of mRNA copied from the DNA base sequences by RNA polymerase.
Translation is the synthesis of polypeptides on ribosomes.
The amino acid sequence of polypeptides is determined by mRNA according to the genetic code.
Codons of three bases on mRNA correspond to one amino acid in a polypeptide.
Translation depends on complementary base pairing between codons on mRNA and anticodons on tRNA.

Applications:

Application: Use of Taq DNA polymerase to produce multiple copies of DNA rapidly by the polymerase chain reaction (PCR).
Application: Production of human insulin in bacteria as an example of the universality of the genetic code allowing gene transfer between species.

Skills:

Skill: Use a table of the genetic code to deduce which codon(s) corresponds to which amino acid.
Skill: Analysis of Meselson and Stahl’s results to obtain support for the theory of semi-conservative replication of DNA.
Skill: Use a table of mRNA codons and their corresponding amino acids to deduce the sequence of amino acids coded by a short mRNA strand of known base sequence.
Skill: Deducing the DNA base sequence for the mRNA strand.

Nature of science:

Obtaining evidence for scientific theories—Meselson and Stahl obtained evidence for the semi-conservative replication of DNA. (1.8)

Use the links to understand of how the evidence Meselson and Stahl obtained supports semi-conservative replication:

Meselson and Stahl explained by Learner's TV

2.7 DNA replication, transcription and translation

2.7 Summary Questions