Chapter 4 - Basic Molecular Genetic Mechanisms
Bases
*PURINES:* A = adenine G = guanine *PYRIMADINES:* U = uracil T = thymine C = cytosine Pairing: A=T (DNA) or C (RNA) C=G
Chemical Structure of DNA strands
- Read from 5" end to 3" end INCLUDES: - *phosphodiester bonds* that link bases - *deoxyribose sugar* (no hydroxyl group on 2' position as in RNA)
The Four Molecular Genetic Processes:
1) *TRANSCRIPTION* copying of DNA to RNA 2) *RNA PROCESSING* modification and transport of RNA 3) *TRANSLATION* synthesis of protein from mRNA 4) *REPLICATION* copying of DNA to DNA
DNA Double Helix
most DNA in cells adopts the *CLOCKWISE RIGHT handed* helical *BETA* form - under some non-physiological conditions, DNA can adopt a left-handed helical structure called *A form DNA* - stands are *ANTI PARALLEL* Calculating Length of DNA Double Helix: - width = 2 nm - length of DNA per helical turn = 3.4 to 3.6 nm - # of bp per turn = 10 to 10.5 - beta form ds DNA: *10.5bp = 3.4 nm* (want to find answer in microns)