Chapter 10 - Molecular Biology of the Gene

Bio 100 - Molecular Genetics 23. Rosalind Franklin and Maurice Wilkins had prepared an X-ray defraction photographof DNA indicating that DNA was long and skinny, helical and consisted of 2 parallelstrandsThe model proposed by Watson and Crick suggested the following features of DNA:1. The DNA molecule is composed of 2 nucleotide chains oriented in opposite directionsIn each strand each P group is attached to one sugar at the 5’ position (the 5th C) and tothe other at the 3’ position2. The DNA molecule is analogous to the structure of a ladderThe bases on the 2 strands are directed inward and form the rung of the ladder, while thesugar-phosphate face outside and act as the sides of the ladder3. Complimentary base pairing - bases A and T always paired and G and C alwayspaired4. They suggested that the two DNA strands are twisted together to form intertwinnedhelices = double helixThe Structure of RNAThe pentose sugar in RNA is riboseThe pyrimidine thyamine is replaced with uracilThus, the 4 bases are: A, U, C, and GRNA is single stranded, and does not form the double helix like DNAThere are 3 different classes of RNA: mRNA, rRNA, and tRNADNA has 2 primary functions:1. To replicate the stored information it contains2. Use the stored information in the synthesis of proteinsCentral Dogma of molecular genetics:DNA ---------------------------> RNA --------------------> proteintranscriptiontranslation