ZOL 341 1st Edition Lecture 2 Outline of Last Lecture I Overview of genetics Outline of Current Lecture II Molecular structure of DNA III Complementary base pairing IV Transcription V Translation VI The genetic code VII Evolution Current Lecture the molecular structure of DNA was key to understanding how DNA could carry genetic information how the molecule replicated Erwin Chargaf for most organisms adenine thymine guanine cytosine nucleotides are arranged as complementary base pairs A with T and C with G DNA nucleotides are composed of a deoxyribose 5 carbon sugar a phosphate group and one of four nitrogenous bases designated Adenine A Guanine G Thymine T Cytosine C These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute complementary base pairing A T G C the 5 and 3 designations of the phosphate and hydroxyl at the ends of the DNA strands establish polarity the two strands are antiparallel micro RNAs active in regulation of gene expression in plants and animals reverse transcription uses an RNA template to produce complementary DNA transcription transcription uses one strand of DNA to direct synthesis of a single stranded RNA transcript template strand DNA strand from which the RNA is synthesized coding strand complementary partner of the template strand translation 5 translation converts mRNA into a sequence of amino acids 5 the resulting polypeptide upon folding makes up all or part of a protein 5 each amino acid is specified by a codon three consecutive nucleotides on the mRNA 5 the genetic code mRNA specifies an amino acid sequence using the genetic code 5 there are 64 possible triplet codons read in the 5 to 3 direction each specifies one amino acid 5 there are 20 common amino acids some amino acids are specified by one codon and others by up to six diferent codons synonymous evolution has a molecular basis life evolves as DNA acquires mutational changes the biochemical processes that replicate DNA and express genetic information are universal evolution the theory that all organisms are related by a common ancestry and have diversified over time natural selection is based on underlying genetic variation as one morphological form is favored over another the frequencies of alleles associated with each form are altered four processes that lead to changes in allele frequencies in a population over time mutation the slow addition of allelic variants that increase the diversity of a population natural selection the diferential reproductive success of members of a species migration the movement of members of a species from one population to another random genetic drift the random change of allele frequencies due to chance in rapidly mating population
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