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Date Submitted: 03/31/2009 08:31 AM
DNA, RNA and Protein (Structure, Composition and Function)
DNA IS A DEOXYRIBONUCLEIC ACID. RNA IS A RIBONUCLEIC ACID.
PROTEIN IS A BUILDING BLOCK OF LIFE, WHICH CONSISTS OF AMINO ACIDS.
We Need Nucleic Acids!
• DNA contains genes, the information needed to synthesize functional proteins and RNAs.
• DNA contains segments that play a role in regulation of gene expression (Transcription and Translation level; promoters, operators, etc.)
• Ribosomal RNAs (rRNAs) are components of ribosomes, playing a role in protein synthesis.
• Messenger RNAs (mRNAs) carry genetic information from a gene to the ribosome.
• Transfer RNAs (tRNAs) translate information in mRNA into an amino acid sequence.
• RNAs have other functions, and can in some cases perform catalysis.
[pic]
Figure 1: RNA and DNA.
[pic]
Figure 2: Structures of DNA.
Figure 3: Structure of RNA.
Nucleotides and Nucleic Acids: Nucleotides are the building blocks of nucleic acids.
Nucleotides have three characteristic components:
A nitrogenous base (Pyrimidines or Purines), A pentose sugar and A phosphate group.
1. The Pyrimidine and Purine Bases (Major Bases in Nucleic Acids)
• The bases are abbreviated by their first letters (A, G, C, T, U).
• The purines (A, G) occur in both RNA and DNA
• The pyrimidine C occurs in both RNA and DNA, but
• T occurs in DNA, and
• U occurs in RNA.
[pic]2. Pentose Sugar: Ribose vs. Deoxyribose.
• An important derivative of ribose is 2'-deoxyribose, or just deoxyribose, in which the 2' OH is replaced with H.
• Deoxyribose is in DNA (deoxyribonucleic acid)
• Ribose is in RNA (ribonucleic acid).
• The sugar puckers in DNA (C-2' endo) and RNA (C-3' endo) are different (Why?)
• The 2’-OH and pucker have a big effect on the double helical structure!
[pic]
3. The Phosphate group
A nucleoside + one or more phosphoryl groups is called a nucleotide....