Biology (Chapter 14)

Used modeling to determine that DNA was helical, and contain two polypeptide chains that run anti paralell in the molecule

English biophysicist that prepared uniform samples of DNA fiber, superior to any previously made

Performed X-Ray Crystollography on a strand of DNA, which helped characterize DNA

Devised a simple experiment to distinguish old strands of DNA from new ones and hence proved that DNA replication is semiconservative

Discovered regularities in DNA; Adenine=Thymine and Cytosine=Guanine

Copying mechanism for the genetic material; each single strand of DN could serve as a guide to produce a new double stranded molecule identical to the original

• Double carbon ring structures
• Adenine and Guanine

• Single carbon ring structures
• Cytosine and Thymine 

• DNA is a template for the reaction
• DNA with and enzyme and 4 precursors (Nitrogen base and sugar, but no phosphate) can replicate itself in a test tube.

Produces two copies that each contained one of the original strands and one new strand

Enzymes unwind the double helix in DNA replication, using ATP energy

An enzyme used in DNA replication

An RNA primer is a short single strand of RNA, this RNA complementary to the DNA template strand is formed by an enzyme-RNA primase 

An enzyme that catalyzes the joining of Okazaki fragments to form one continuous DNA lagging strand

The template strand of the DNA double helix so that the replication fork moves along it in the 3' to 5' direction

Strand that is being built from the replcation fork 5' to 3', but has to wait for a nitrogen base to be exposed

Newly synthesized stretches of lagging strand DNA

• Mechanisms that fix DNA strands that have flaws 
• Proofreading- removes improper nucleotide and retries
• Mismatch Pair- detects "wrong" bases

If DNA becomes damaged during the life of the cell, certain enzymes "inspect" the cell's DNA

Moving Y shaped structures tha tare the regions where new DNA strands are being synthesized 

Helicases act at a specific point on the DNA, which is circular; this point is called an origin of replication.

DNA is linear but replication does not begin at the ends of the molecules; each eukaryotic chromosome has many origins of replication

A region of repetitive nucleotide sequences at each end of a chromosome, which protects the end of the chromosome from deterioration or from fusion with neighboring chromosomes

A ribonucleoprotein that is an enzyme which adds DNA sequence repeats ("TTAGGG" in all vertebrates) to the 3' end of DNA strands in the telomereregions, which are found at the ends of eukaryotic chromosomes

...Blast a cell with UV light so that 99 per cent of the cell, including its DNA, is destroyed, you can almost entirely repair the damage in a single day just by illuminating the cell with the same wavelength at a much weaker intensity.