Molecular biology 10 th grade bio

DNA and RNA DNA stands for Deoxyribonucleic acid RNA stands for ribonucleic acid RNA is a molecule found in everything living or once was living DNA is a molecule found in everything living except primitive bacteria and archaea

Leading up to discovering DNA (191) 1928 Frederick Griffith experiment – His big findings was that a dead bacteria could pass on its genes to live bacteria – He did not know how it worked but guessed the dead bacteria give the live bacteria some kind of molecule

Leading up to discovering DNA (192) Hershey and Chase experiment in 1952 – Determined DNA carried genetic material NOT proteins! – Very controversial because DNA has only 4 nucleotides and proteins has 20 amino acids

Hershey-Chase Experiment Used a bacteria phage with two sections. – Body (proteins) – DNA Made each radioactive so could observe. Found DNA is left in the host so new phages could reproduce

A race After the shock of DNA being the genetic molecule a fierce race was started to determine what its structure looked like. This was a big deal in the science world. The big players were – James Watson & Francis Crick – Linus Pauling – Rosalind Franklin & Maurice Wilkins

Watson & Crick The front runners in determining the structure. Worked in the late 1940’s and early 1950’s Determined the double helix structure in 1953 Awarded Nobel prize in 1963 Could not do it without “stealing” others work

Rosalind Franklin & Maurice Wilkins Franklin was a female scientist in a male ran world. Worked as a grunt for Wilkins lab and did her own side projects. – Worked with x-ray diffraction Wilkins got his hands on some of her work and showed it to Watson & Crick which led them to determine the structure of DNA Died in 1958 from ovarian cancer from working with radiation in her research Never received a Nobel prize for her work

DNA Structure Sugar & phosphate backbone Nucleotide bases in the middle – Cytosine – Thymine – Adenine – Guanine Run anti-parallel

DNA Structure Three main elements in DNA’s chemistry – Phosphate= in the backbone – Carbon (sugar)= in the backbone – Nitrogen= nucleotides

Nucleotides Purines – Adenine – Guanine Pyrimidines – Thymine – Cytosine

Pairing base rules Chargaff’s rule (1949) – The amount of adenine = thymine and the amount of guanine = cytosine – The total of all four bases must equal 100% – The percentages change depending on the species – In humans you have 29% adenine how much thymine of you have? How much cytosine? – Yeast has 33% thymine how much guanine do they have?

DNA has two strands DNA strands run anti-parallel and complement each other. If you have a DNA strand with the sequence what is the stand that complements it? 3’ TTAGGCTACG 5’

Possible replication models Write what happens in the three different types of models. (make observations)

Meselson and Stahl experiment Supported the hypothesis of the semi-conservative model. – Radioactive DNA that was heavy and not heavy.

Replication fork

Leading strand Lagging strand Template strand New DNA

Major players in replication DNA Helicase- unwinds and opens the double helix – Breaks bonds between the nucleotides DNA polymersase- moves along open strands and adds nucleotides to old strands. – Only can lay nucleotides 5’ to 3’ direction Okazaki fragments- section of DNA during replication that is on lagging strand

Transcription and Translation