DNA DNA spells

Bellringer How are photosynthesis and the calvin cycle connected? How do they relate to glycolysis, citric acid, and ETC?

Nucleic Acids DNA – the genetic code for ALL proteins RNA – the code for ONE protein ATP - Energy All are made of nucleotides

Eukaryotic DNA Structure We have 46 strands of it – called chromosomes 23 from mom, 23 from dad If it is damaged it can be: Repaired by DNA polymerase Cancer Cell death

Prokaryotic DNA Structure

Prokaryotic DNA Structure Nucleoid Just one chromosome Closed in a circular loop Remember – these are very simple organisms with no lipid bound organelles – they don’t need the code for much

Viral Genetic material Can be one small strand of DNA or several small strands Can be 5,000 nitrogen bases or millions (we are billions long) Can be: Double stranded DNA Single stranded DNA Single stranded RNA Double stranded RNA Viruses are jerks and break all the rules 

Nucleotides Phosphate group – acts to hold the sugars together Sugar – Deoxyribose in DNA, Ribose in RNA and ATP nitrogen bases Adenine, Guanine, Cytosine in both Thymine in DNA Uracil in RNA

The backbone of DNA Phosphates and sugars bind together The bond between a sugar and a phosphate is called PHOSPHODIESTER BOND 5’ – 3’ Backbone protects nitrogen bases

Nitrogen bases Adenine and Guanine “Large” nitrogen bases Purines Pyrimidines Adenine and Guanine “Large” nitrogen bases Adenine binds with thymine in DNA/ Uracil in RNA Guanine binds with cytosine Cytosine, Thymine, and Uracil “Small” nitrogen bases Cytosine binds with guanine Thymine is only in DNA and binds with adenine Uracil binds with adenine in RNA

Nitrogen bases Purines Pyrmidines

How do they bind? Covalent bond from sugar to nitrogen base Hydrogen bonds connect nitrogen bases This leads to two strands of DNA The shape is called a DOUBLE HELIX

How did we find it out? NOT WATSON AND CRICK IT WAS A WOMAN NO ONE EVER TALKS ABOUT HER AND IT MAKES ME SO ANGRY ROSALIND FRANKLIN FO LYFE DON’T TELL ME WHAT YOU CAN’T DO

How did we build what DNA looks like? Watson and Crick thought purines bound to purines, and pyrimidines to pyrimidines Rosalind Franklin knew it was bogus –the model didn’t fit She took a sample of DNA and saw it was an even tube

Chargaff’s Rule The percentage of nitrogen bases must equal their complements By knowing the percentage or amount of one nitrogen base you can find all others Example: If you find that an animals has 30.3% adenine, what are its concentrations of: G C T

DNA Replication In organic chemistry we number the carbons This lets us show which carbons are bonded Deoxyribose sugar can bind to phosphates at the 5’ or 3’ carbon THIS DETERMINES THE SHAPE OF DNA

DNA Replication Antiparallel elongation – the two strands run paralell, but in opposite directions One goes from 5’3’ while the other goes 3’5’ The enzyme which replicates DNA can only go from 3’ to 5’ …what about the 5’3’ strand?

Strands Leading Strand Lagging Strand 3’5’ Has one primase added and DNA Polymerase III is able to continue unhindered 5’3’ Is going against the grain Requires several primases Contains okazaki fragments

Enzymes for laggers AND leaders Helicase – unwinds the DNA by cutting the hydrogen bonds between nitrogen bases Single – Strand Binding Proteins – hold the DNA open after the strands are split Topoisomerase – relieves the tention caused by unwinding DNA

Enzymes Leading Strand Lagging Strand Primase – adds the RNA primer at the 5’ end so replication can begin DNA Pol III – continuously synthesizes the leading strand from 3’-5’ DNA pol I – removes primer from 5’ end and replacing it with DNA DNA Ligase – joins the 3’ end added by DNA pol I to the leading strand added by DNA pol III Primase – adds the RNA primer at the 5’ end of each okazaki fragment DNA Pol III – elongates each okazaki fragment DNA pol I – Replace primers with DNA DNA Ligase – Joins okazaki fragments

Leading and Lagging strands One runs on the 3’5’ TEMPLATE strand adding a NEW 5’3’ strand Going in the other direction polymerase can’t create one large strand, instead it makes fragments called okazaki fragments

Replication Fork

Lets put this in perspective… Helicase cuts the hydrogen bonds. Topoisomerase relieves the tension. SSBP’s hold it open Primase adds a primer of RNA that signals DNA Polymerase III to attach and add nucleotides in a 5’3’ direction to the 3’5’ template DNA Pol I removes the RNA primer and replaces it with DNA DNA Ligase binds the gaps together

How is DNA repaired? DNA is mismatched. How can we fix it? Nuclease cuts out the bad section DNA Pol III puts in the right nucleotides Ligase stiches the new chunk to the old

Aging Each time DNA replicates a strand shortens. DNA polymerase can’t start with a 3’ end. It must start at the 5’ template end. This causes a shortened end. Telomerase can lengthen the strand back to its original length but is not normally active. It IS however active in cancer cells, they reproduce forever

Aging