DNA
Basic info about DNA
- long linear polymers, called nucleic acids.
- Carry info from one generation to the next.
- Macromolecules that consists of large number of linked nucleotides, each composed of a sugar, a phosphate and a base.
- Sugar-phosphate backbone → play structural role.
- Sequence of bases along nucleic acid chain → carries genetic info!
- DNA as shown in pic's above → double helix, with 2 complementary nucleic acid strands.
- Each strand serves as a template for DNA replication
Nucleic Acid
- DNA
- RNA
- Friedrich Miescher discovered DNA in 1869, he identified a novel phosphorus-containing substance from the nuclei of white blood cell found in waste surgical bandages.
- It was found that both these are acidic molecules, they release hydrogen ions (H+) in sol, and have a net negative charge at neutral pH, therefore the name nucleic acid.
DNA- Double Helix
- To form the strand of DNA, nucleotides are linked into chains, with the phosphate and sugar group alternating producing a phosphodiester bond (covalent)
- Complementary bases pair through weaker hydrogen bonds
- Key property: complementary base pairing and consequences (1:1 ratio of A:T and of C:G therefore 1:1 purines: pyrimidines -> Chargaff's rule), constant width across mol
- 2 strands of DNA can hydrogen-bond with each other to form a double helix.
- In living cells, DNA is associated with an array of different proteins to form chromosomes. The association of proteins with DNA organises the long strands into a compact structure.
- A genome is a complete complement of an organisms genetic material
Finding the other strand
e.g. Find the reverse complement of: 5' - CTAGCCC -3'
e.g. Find the reverse complement of: 5' - CTAGCCC -3'
- First reverse the sequence: 5' - CCCGATC - 3'
- Then find the complement: 5' - GGGCTAG - 3'
DNA Replication
- Bacterial cell (around 1 to 5 million bp)
- Generation time → around 20 min
- DNA replication → incredibly sophisticated, efficient, precise, highly coordinated series of molecular events.
- Eukaryotic DNA replication → much more complex (not all resolved!)
- In the notes only talked about prokaryotic DNA replication not eukaryotic (as not understood well!)
Biochemical Identification of the Genetic Material
- Heredity → Tendency of an organism to possess the characteristics of its parents
- Genetic material → ??? chemical identity, didn't know until 1950!
- Information → Must contain the info required to construct an entire organism
- Replication → Capable of precise copying/replication of genetic info, so info is not lost of altered
- Transmission → Able to be passed from parent to offspring during reproduction and also be able to pass from cell to cell during cell division.
- Variation → Differences in genetic material must account for the known variation within each species and among different species.