1. THE MOLECULAR BASIS OF INHERITANCE

2. ANNOUNCEMENTS Second set of genetics problems has been posted!!

3. 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 20 th century Understand relevant vocabulary

4. THE MOLECULAR NATURE OF GENES By early 1900s: The fact that chromosomes are responsible for heredity is known

5. THE MOLECULAR NATURE OF GENES First Half of 1900s: –Dominated by research on what genes are composed of and how they work

6. COMPOSITION OF GENES: DNA Hershey & Chase (1952):

7. DETERMINING THE STRUCTURE OF DNA James Watson & Francis Crick (1953):

8. HOW GENES FUNCTION Beadle &Tatum (1941): :

9. THE GENETIC CODE How do we go from DNA to protein? DNA RNA Protein

10. THE CENTRAL DOGMA Francis Crick:

11. THE GENETIC CODE George Gamow:

12. How many bases specify a single amino acid? 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. 1 Base? 2 Bases? 3 Bases? 4 Bases?... 4 < 20: Not enough 16 < 20: Not enough 64 > 20: More than enough 1234 1 2 34 5 6 78 9 10 1112 13 14 1516 1 2 34 5 6 78 9 10 11 12 13 14 15 etc... U GCA U G C A U G C A U G C A U G C A U G C A U G C A U G C A U C A U C AG U C AG U C AG U C AG U C AG U CAG U CAG U CA U G C A U G C A U G C A U C A mRNA G C C A C C G A G A A A A A A A A A A U U U U U U U U U C C C C C C C C C CC C G G G G G G G G FOUR RNA BASES (U,C,A,G) MUST SPECIFY 20 AMINO ACIDS

13. DECIPHERING CODONS Codon:

14. THE GENETIC CODE Recent Work: