DNA Structure and Replication

DNA stores a cell’s genetic information that is used to make proteins. Proteins result in the expression of different phenotypes.

DNA Deoxyribonucleic Acid

The monomers that make it up are nucleotides DNA is a polymer. The monomers that make it up are nucleotides Each nucleotide has three parts: 5 carbon sugar – deoxyribose Phosphate group Nitrogen-containing base

A Nucleotide

The Nitrogen-Containing Bases:

The purines: The pyrimidines:

Chargaff’s Rule

The DNA molecule: http://www3.interscience.wiley.com:8100/legacy/college/boyer/0471661791/struc ture/dna/dna_intro.htm

DNA Replication Process by which DNA is copied. The DNA template (old DNA) is used to create DNA that is identical to the original DNA. This must occur before the mitosis occurs, so that each daughter cell has identical DNA.

The process of Replication 1. DNA Helicase breaks the hydrogen bonds between the nitrogen bases, causing the DNA to unzip. Producing the replication fork.

2. DNA Polymerase attaches an RNA primer at a certain point (the origin). The RNA primer starts the replication process.

3. DNA Polymerase begins adding free-floating nucleotides along the DNA template, starting at the RNA primer. The nucleotides are added in the 5’ to 3’ direction. http://highered.mcgraw-hill.com/sites/0072437316/student_view0/chapter14/animations.html#

Because the nucleotides can only be added in one direction, one strand has nucleotides being added in a continuous strand = Leading strand, while the other is copied in small pieces = Lagging strand. The small pieces on the Lagging Strand are called Okazaki fragments.

4. DNA ligase fills in gaps between the Okazaki fragments on the lagging strand and promotes the formation of covalent bonds between sugars and phosphate groups. http://www.johnkyrk.com/DNAreplication.html http://www.stolaf.edu/people/giannini/flashanimat/molgeneti cs/dna-rna2.swf

DNA replication is “semi-conservative”.