• DNA and RNA structure
• Complementary base pairing
• DNA replication
• Transcription - DNA to mRNA
• mRNA maturation
• Translation - mRNA to polypeptides

• Purine and Pyrimidine bases,2-deoxyribose sugar, phosphate
• Double stranded molecule
• Antiparallel orientation of strands
• double helix
• ca. 10 bp per turn
• hydrogen bonding in base pairs: A-T, C-G

• Replication is semiconservative
• Replication proceeds from 5’ to 3’
• DNA polymerase and other enzymes

• DNA from one strand (coding strand) is transcribed into mRNA.
• RNA polymerase
• RNA - ribose instead of deoxyribose - uracil instead of thymine
• mRNA is single stranded and the strand grows from 5’ to 3’

• Intervening sequences (introns) must be removed and coding regions (exons) must be spliced together.
• The maturing transcript is also capped and polyadenylated
• mRNA must leave the nucleus

• The genetic code consists of triplets of nucleotides (codons) along the mRNA strand.
• There are 43=64 possible codons.
• tRNAs have an anticodon loop that base pairs with codons
• tRNAs carry specific a.a.’s that are added to the growing polypeptide chain

• tRNA’s dock with the ribosome
• the ribosome has a "p" site and an "a" site
• The start codon is AUG (methionine)
• There are several stop codons
• DNA and polypeptides are co-linear; 5’ to 3’ and N (amino terminus) to C (carboxy terminus)

• Genes may be regulated at the
• Transcriptional level and the
• Translational level
• Genes may be re-arranged
• Genes may be chemically modified at the DNA

• Problem: You wish to study a particular gene
• Given: The same (more or less) or similar genes occur in species as diverse as slime molds and humans.
• If, you know something about the sequence of gene based on some other organism

• Then, you can use this information to isolate (clone) your gene via PCR

PCR takes advantage of thermostable DNA polymerases isolated from certain bacteria that live in extremely hot environments (extremophiles)