#samtalksbio

The lagging strand is (and I quote Hank Green @edwardspoonhands of CrashCourse Biology) a total “scumbag,” don’t trust him at all. He does everything backwards in terms of DNA replication and makes life harder for students The leading strand, now THAT one knows how to get work done and make things easier for students But unfortunately we still need both strands so we gotta deal with the lagging strand :’(

Prokaryotes have three types of DNA polymerase: I, II, and III (go figure) I is used to replace primers and mistakes II is for DNA repair III is for the main replication of the genetic code i.e. adding the nucleotide bases on the new/daughter strand of DNA I’m not even gonna begin to talk about 5’–>3’ and all that because its too much work to type it all out and it isn’t too difficult imo. The main part is that DNA polymerase I also has 5’ to 3’ exonuclease activity as well as 3 to 5 (II and III only have 3 to 5) Exonuclease activity in a nutshell is just going backwards (3 to 5) along the new DNA strand and fixing mistakes (normally the polymerase activity is 5 to 3 so in order to fix mistakes it has to go backward aka 3 to 5)

There are six main types of ribonucleic acids (RNA’s): Messenger, or mRNA Ribosomal, or rRNA Transfer, or tRNA Small Nuclear, or snRNA Micro, or miRNA and Signal Recognition Particle RNA And all of these different RNA’s are synthesized via transcription (which is a whole nother process entirely) from the DNA in the nucleus. Speaking of which, the strand of DNA that RNA polymerase acts upon and binds to in order to produce RNA is called the template strand (because it is the basis of the RNA) and the other, untouched strand is called the coding strand (because its nucleotide code/nitrogen bases more or less are identical to the RNA except for thymine being replaced with uracil)

The genetic code is degenerate, meaning multiple RNA codons can code an amino acid (but 1 RNA codon can’t code multiple amino acids) Start mRNA codon: AUG –> Methionine Stop mRNA codons: UAA (U Are Annoying), UGA (U Go Away), and UAG (U Are Gone) –> no Amino Acids supplied The genetic code is also universal, meaning all known forms of life use the same DNA and RNA nucleotides (adenine, thymine, guanine, cytosine, uracil) except for a few extremely rare exceptions.