2.  After describing the structure of DNA, they released a second paper ◦ Basically stated that the base pairing model indicated a method for replication  Each strand would serve as a template for a new companion chain, called the complement

4.  As a result, each daughter strand has a strand from the original molecule  This is referred to as semi-conservative replication  So, from the parent strand, new bases are added to added according to the base pairing model  A strand of ATTCGACT would match up with TAAGCTGA

5.  A wide variety of enzymes are used during the replication process (recall anything ending in –ase is an enzyme)  The enzyme that opens the parent molecule by breaking the hydrogen bonds is helicase  It “unzips” the molecule  The other principle enzyme is DNA polymerase (actually three variations on it!)  It moves along the unwound strand, adding the appropriate bases

6.  Another version of the polymerase “checks” to ensure that no mistakes were made

8.  Now that we know the structure of DNA, we can analyze how proteins are made  Broken down into two processes: transcription and translation  This is where RNA is used in our body  Structurally, RNA contains a ribose sugar ◦ The 2’ carbon contains a hydroxyl group as opposed to a hydrogen

10.  Additionally, RNA tends to be single stranded, and contains a uracil in the place of thymine

11.  In protein synthesis, three unique types of RNA are used: Messenger RNA (mRNA)  RNA copy of the DNA strand to be “read” during translation Transfer RNA (tRNA)  Carries individual amino acids to site of replication

12. Ribosomal RNA (rRNA)  Attached to ribsome complex, site of protein synthesis rRNA tRNA

13.  A complementary strand of mRNA is made, first by unzipping the DNA molecule ◦ This time, by RNA polymerase  This only happens on specific regions of DNA known as promoter regions  That way, it isn’t just a random region  Similar regions cause the transcription process to stop

14.  Certain regions of DNA do not code for any proteins that we use, called introns ◦ We mentioned these before as the “junk” regions  The introns must be spliced out, joining all the coding regions known as exons  Finally, a 5’ cap and poly A tail must be tacked on to the ends to finish the editing process

16.  The processed mRNA is now reading to be decoded  The “language” is spoken in three base “words”

19.  Translation begins when the mRNA binds to the rRNA on a ribosome  This moves along the sequence until an AUG codon is found ◦ This is the start codon, and the methionine code, hence all protains begin with Met  tRNA then attaches and drops off the appropriate amino acid ◦ It does this by have a matching anticodon  Sequential amino acids are linked by peptide bonds ◦ So, it is called a polypeptide

20.  This process continues until a stop codon is found  Polypeptide and mRNA are release  Polypeptide goes through up to four stages of folding to become a mature protein