3 Main Questions:
- What is transformation?
The conversion of a normal animal cell to a cancerous cell. A change in genotype and phenotype due to the assimilation of external DNA by a cell.
- What is a double helix?
The form of native DNA, referring to its two adjacent antiparallel polynucleotide strands wound around an imaginary axis into a spiral shape.
- What is helicase?
An enzyme that untwists the double helix of DNA at the replication forks, separating the two strands and making them available as template strands.
5 Main Facts:
- The relationship between structure and function is manifest in the double helix.
- The replication of a DNA molecule begins at special sites called origins of replication.
- Enzymes called DNA polymerase catalyze the synthesis of new DNA by adding nucleotides to a preexisting chain.
- At each end of a replication bubble is a replication fork, a Y-shpaed region where the parental strands of DNA are being unwound.
- Most DNA polymerase require a primer and a DNA template strand, along which complenmentary DNA nucleotides line up.
Diagram:
The diagram shows the base pairing in DNA. The pairs of nitrogenous bases in a DNA double helix are held together by hydrogen bonds, shown here as dotted line. The parent molecule has two complementary strands of DNA. Each base is paired by hydrogen bonding with its specific partner, A with T and G with C.
Summary:
James Watson and Francis Crick shook the scientific world with an elegant double-helical model for the structure of deoxyribonucleic acid, or DNA. Of all nature's molecules, nucleic acids are unique in their ability to dsirect thier own replication from monomers.
The replication of a DNA molecule begins at special sites called origins of replication, short stretches of DNA having a specific sequence of nucleotides. DNA replcation recognize this sequence and attach to the DNA, separating the two strands and opening uo a replication "bubble".
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