Topic 7.1: DNA Structure and Replication 

Essential Idea:  The structure of DNA is ideally suited to its function.
At SHS, Topic 7.1 is taught in the following class unit(s):

Statements & Objectives:

7.1.U1  DNA structure suggested a mechanism for DNA replication.
  • Outline the features of DNA structure that suggested a mechanism for DNA replication.
7.1.U2  Nucleosomes help to supercoil the DNA.
  • Draw and label the structure of a nucleosome, including the H1 protein, the octamer core proteins, linker DNA and two wraps of DNA.
  • Explain the levels of supercoiling (DNA→ nucleosome → beads on a string → 30nm fiber →  unreplicated interphase chromosome → replicated metaphase chromosome).
7.1.U3  DNA replication is continuous on the leading strand and discontinuous on the lagging strand.
  • Compare replication on the the leading strand and the lagging strand of DNA.
  • Explain why replication is different on the leading and lagging strands of DNA.
  • Outline the formation of Okazaki fragments on the lagging strand.
7.1.U4  DNA replication is carried out by a complex system of enzymes.
  • Outline the role of the following proteins in DNA replications:  helicase, topoisomerase (AKA gyrase), single stranded binding proteins, primase, DNA polymerase III, DNA polymerase I, and DNA ligase.
7.1.U5  DNA polymerases can only add nucleotides to the 3’ end of a primer.
  • Explain the need for RNA primers in DNA replication.
  • Explain what is meant by DNA replication occurring in a 5' to 3' direction.
7.1.U6  Some regions of DNA do not code for proteins but have other important functions.
  • Define “coding sequences” and “repetitive sequences” of DNA.
  • Outline five functions of non-coding DNA sequences found in genomes, one of which must be the telomere.
7.1.A1  Rosalind Franklin and Maurice Wilkins’ investigation of DNA structures by X-ray diffraction.
  • Outline the process of X-ray diffraction.
  • Outline the deductions about DNA structure made from the X-ray diffraction pattern.
7.1.A2  Tandem repeats are used in DNA profiling.
  • Define VNTR.
  • Explain why VNTR are used in DNA profiling
7.1.A3  Use of nucleotides containing dideoxyrubonucleic acid to stop DNA replication in preparation of samples for base sequencing.
  • Outline the process of DNA sequencing, including the role of chain terminator nucleotides, fluorescence, and electrophoresis.
7.1.S1  Analysis of results of the Hershey and Chase experiment providing evidence that DNA is the genetic material.
  • State the experimental question being tested in the Hershey and Chase experiment.
  • Explain the procedure of the Hershey and Chase experiment.
  • Explain how the results of the Hershey and Chase experiment supported the notion of nucleic acids as the genetic material.
7.1.S2  Utilization of molecular visualization software to analyze the association between protein and DNA within a nucleosome.
  • Identify nucleosome structures using molecular visualization software. 
  • Outline the mechanism of histone-DNA association.
7.1.NOS  Making careful observations-Rosalind Franklin’s X-ray diffraction provided crucial evidence that DNA is a double helix.
  • Describe Rosalind Franklin’s role in the elucidation of the structure of DNA.
"When we try to pick out anything by itself, we find it hitched to everything else in the Universe." 
 John Muir,   1911