DNA: Structure and Replication

DNA and RNA Structure

I AM ABLE TO: Describe DNA, its shape, and how it creates more of itself.

• Both DNA and RNA are Nucleic Acids.
  
• Monomers are nucleotides.
  
• There are three components of a nucleotide: a sugar, a phosphate group, and a nitrogenous base.


• The Four nitrogenous Bases of DNA: Adenine, Guanine, Cytosine, and Thymine(RNA has uracil instead of thymine).


• The nucleotides in DNA are joined by covalent bonds between the nitrogenous base, and the sugar.
  
  
• The "backbone" of the structure is made of a pattern of "sugar-phosphate-sugar-phosphate".


• The sugar in DNA is deoxyribose.
• DNA= deoxyribonucleic acid.
  
  

Watson and Crick and the Double Helix

• The two have been credited for the discovery of DNA's double-helix structure.


• Watson first perceived it from a X-ray crystallographics photo by Rosalind Franklin.
Watson and Crick constructed a model using wires

They used the information from Franklin's data, as well as the current chemical knowledge of DNA.


With their models, they came up with the concept of specific base pairings.

Adenine pairs with Thymine (DNA, Uracil in RNA), and Guanine pairs with Cytosine.

DNA Replication

• Replication is the process in which more DNA is made.

• An enzyme called helicase starts at the origin of replication, and untwists the the DNA strands.

• This becomes the "replication bubble"

• Then the enzyme DNA polymerase follows and adds complimentary DNA nucleotides to the two opposite strands. (One of the old DNA strands will be used as the template for the new DNA strand.)

The product is two DNA strands, each with a new and old strand of nucleotides.

There are many replications happening at the same time, and at very fast rates.

Replication ensures that the DNA in a multicellular organism's cells are the same.

Strand:Life and Environmental Sciences

Standard 5: Life and Environmental Sciences: DIVERSITY, GENETICS, AND EVOLUTION: Understand genetics and biological evolution and their impact on the unity and diversity of organisms.

Topic: Unity and Diversity

Benchmark SC.BS.5.3 Explain the structural properties of DNA and the role of DNA in heredity and protein synthesis.


All pictures from:http://wps.aw.com/wps/media/objects/3037/3110897/ebk/htm/_eb3e.htm?10