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THE MOLECULAR BASIS OF INHERITANCE. ANNOUNCEMENTS. Second set of genetics problems has been posted!!. OBJECTIVES. Know the structure of DNA Understand the relationship between genes and proteins
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ANNOUNCEMENTS • Second set of genetics problems has been posted!!
OBJECTIVES • Know the structure of DNA • Understand the relationship between genes and proteins • Be familiar with scientists that contributed to the field of molecular genetics in the early mid 20th century • Understand relevant vocabulary
THE MOLECULAR NATURE OF GENES By early 1900s: • The fact that chromosomes are responsible for heredity is known
THE MOLECULAR NATURE OF GENES First Half of 1900s: • Dominated by research on what genes are composed of and how they work
COMPOSITION OF GENES: DNA Hershey & Chase (1952):
DETERMINING THE STRUCTURE OF DNA James Watson & Francis Crick (1953):
HOW GENES FUNCTION Beadle &Tatum (1941)::
THE GENETIC CODE How do we go from DNA to protein? DNA RNA Protein
THE CENTRAL DOGMA Francis Crick:
THE GENETIC CODE George Gamow:
FOUR RNA BASES (U,C,A,G) MUST SPECIFY 20 AMINO ACIDS How many bases specify a single amino acid? G G C A U A C G A G U C C G C G U U A A G C U A U mRNA C G A A A U A A G U C C C A C G C G C C C U C 3 Bases? 2 Bases? 1 Base? 4 Bases?... Since there are only 4 bases, a singlet code could only specify 4 amino acids. A doublet code could specify a maximum of 4 x 4 or 16 amino acids. A triplet code could specify a maximum of 4 x 4 x 4, or 64 amino acids. C U A U U G U U U U U U C U U U U A U G C A G U 2 1 2 3 4 3 4 1 1 2 3 4 C C A C C G C C U C C C C C C C C U A G 4 < 20: Not enough 6 5 7 8 6 5 7 8 A A A C U A G A A A A A A A A A C A G U 9 9 11 12 10 11 10 12 A G C G G G G U C G G A G G U G G etc... 14 14 13 15 16 15 13 16 < 20: Not enough 64 > 20: More than enough
DECIPHERING CODONS Codon:
THE GENETIC CODE Recent Work: