Chapter 12 Biology Mr Wright DNA, RNA, Proteins Chapter 12 Biology Mr Wright

Objectives Tell how historical discoveries that lead to DNA build on technology and previous knowledge Use a model to describe the structure of DNA Explain the importance of DNA replication in cell reproduction Summarize how genetic information in DNA gets made into proteins. Replication, Transcription, Translation Prepare a position about intentionally modifying/mutating chromosomes. Defend/support your opinion. Describe how mutations may affect genetic expression Cite examples of mutagens.

Discovery of DNA Dr Meischer in Germany, while looking at bandages of surgical patients, identifies nuclein, or DNA. 1890s Griffith found dead pneumonia bacteria transferred something to harmless living bacteria.  1928  Avery McCarty, McCleod identified DNA as the genetic material, by eliminating carbs, then lipids, then proteins, then RNA, then DNA from a pneumonia bacteria in mice, found DNA is the genetic material, not protein. 1944

DNA discoveries Chargaff discovers Nitrogen bases bond together Cytosine and Guanine, and Thymine and Adenine, based on Percent abundance.  Hershey & Chase use radioactive elements and Virus to infect bacteria. They found that Phosphorus went into the Bacteria and Not Sulfur. Franklin and Wilkins Xray photograph DNA showing it's a double helix. Watson and Crick used the previous discoveries to make a model of DNA. 

DNA model Nitrogen bases (Adenine, Thymine, Cytosine, Guanine) Phosphate Deoxyribose sugar Double helix is twisted ladder

DNA Purines form hydrogen bonds with Pyrimidines Purines: Adenine, Guanine Pyrimidines: Thymine, Cytosine

Why the nitrogen bases?  The order in DNA determines your traits and cell parts, like black hair or blonde hair. 

DNA pairing order A to T C to G

What bases bond to this strand of DNA? ATC CTA GGC  GAT TAA

DNA needs copied to go into new cells Semiconservative replication One side is kept in the new DNA strand. Bacteria have circular DNA Eukaryotes have strings of DNA

3 steps in DNA replication Unwind with DNA helicase (unzip) Bases pair up A-T and C-G with DNA polymerase enzyme Enzyme ligase glues to two strands together. Some parts bind backwards and are called Okazaki Fragments.  https://www.youtube.com/watch?v=G1AoVF3k9Hg

DNA transcription is making a messenger for a gene that codes for a protein. 

DNA transcription RNA polymerase unzips DNA A single strand is made from one side of DNA RNA has Uracil instead of Thymine, is single stranded.  In Eukaryotes it exits the nucleus and is cut up into Exons.  TAC AAT TTT CGA (DNA makes the below RNA strand) AUG UUA AAA GCU https://www.youtube.com/watch?v=kF7csBG1fgo&t=17

Exons and Introns Exons exit the nucleus, Introns stay in the nucleus RNA processing in humans removes introns, after RNA is made. 

DNA to RNA to Proteins This process is called the Biology central dogma.  DNA is the master copy of our body RNA is the worker/construction worker Proten is the structure

3 Steps in Translation Messenger RNA has a three base code called an Anticodon attach Transfer RNA is a T shaped RNA RNA has an amino acid on TRNA Ribosomes attach TRNA and mRNA

Translation Once the mRNA is synthesized, it leaves the nucleus in eukaryotes and enters the cytoplasm. The 5' end of the mRNA connects to the ribosome, where the code is read and translated to make a protein in a process called translation. IN translation, tRNA interprets the mRNA codon sequence. Once the mRNA binds with a ribosome, a tRNA with the anticodon, UAC will bind to the mRNA start codon AUG. 

We use a chart to tell what amino acids are made

Mutations Gene regulation is the ability of an organism to control which genes are transcribed.  An operon contains the genes for the proteins in an organism. An operator is a segment of DNA that turns on or off the transcription to RNA Eukaryotes control gene expression using transcription factors Hox genes control the body plan of an organism

Mutations Point mutations change one amino acid or nitrogen base Substitution mutations change an amino acid for another Frame shift mutations move the three letter bases over one or more places. 

Mutations Xrays Gamma rays UV rays Some chemicals can cause mutations. Alcohol Illegal Drugs