Chapter 10- DNA, RNA and Protein Synthesis

There are 2 Nucleic acids in a cell: Deoxyribonucleic Acid -DNA- 2. Ribonucleic Acid -RNA-

10.1 – DNA Information DNA discovery: 1950s Mr. Watson and Mr. Crick used X-rays of DNA crystals to show the structure of the molecule - X-rays were taken by Rosalind Franklin and Maurice Wilkins

Model is called the Watson-Crick model Shape – 2 sided and twisted – DOUBLE HELIX

DNA

DNA Structure DNA is a Polymer Monomers of DNA are ___________

Nucleotide has 3 parts: Sugar – named deoxyribose - (pentose) Phosphate group – phosphoric acid (phosphate bonded to 4 oxygen atoms) Nitrogenous base – contain Nitrogen and carbon atoms

Structure of a Nucleotide

Nitrogen BASES

Nitrogen BASES: 2 sizes (p 198) Larger – structural formula shows double-ring Called PURINES Ex: Adenine (A) & Guanine (G) Smaller – structural formula shows single ring -Called PYRIMIDINES -Ex: Cytosine (C) & Thymine (T) -Ex Uracil(U) in RNA, but NOT in DNA

BASES will chemically bond only w/ certain other bases. Always makes pairs of bases w/ A – T C – G Bases bond w/ weak Hydrogen bonds

DNA Base Pairs

DNA Replication The double-strands of DNA make a replication mechanism intuitive! The DNA unwinds and each strand re-pairs with new matching nucleic acids. Uses helicase and DNA polymerase

How is information stored? DNA is broken down into regions called genes that are the key programs in determining how an organism functions. Promoter Operon Gene 1 Gene 2 Gene 3

How are genes used? The promoter region signifies the beginning of a group of genes, and the operon determines when they are allowed to be used. Using a gene involves two steps: transcription and translation.

10.3 - Protein Synthesis Where: Ribosomes Why:

What: Protein chem. review Building Blocks (monomers) = aa ______ different kinds ______ usual name ending Proteins are polymers = _______________ Includes 100’s of monomers bonded together. Symbol: aa + aa + aa + aa + aa + …. = Polypeptide chain Held together w/ ________bonds.

2 parts to Protein Synthesis 1. Transcription- copying of DNA code into mRNA codons 2. Translation-The process of assembling polypeptides using codons on mRNA.

Transcription Steps: RNA polymerase moves to a specific area on a DNA where the copying begins called the promotor. The DNA “unzips” at the promoter site. The side of DNA that will be used to make RNA is called the TEMPLATE. mRNA forms chains of nucleotides following the BASE PAIRING RULE.( The “copying: procedure is like replication except NO thymine is used, but INSTEAD RNA uses URACIL. )

4. The copying continues until a site on the DNA called the TERMINATION SIGNAL is reached the procedure now STOPS. The newly made mRNA now moves away from the template and leaves the nucleus. The “genetic code” or sequence of BASES on the mRNA will determine which aa is used to make the protein.

The Genetic Code

Proteins differ from each other by: Size – use a different number of aa. The more aa the larger the protein. Chemistry- Use dif. aa from each other (some proteins are “incomplete”, usually from plants) Ex: aa1 + aa20 + aa3 + aa4 …. vs. aa1 + aa20 + aa13 + aa4 ….    Put same aa in a dif. order or sequence.    Ex: aa1 + aa20 + aa3 + aa4 …. aa20 + aa3 + aa1 + aa4 ….     aa = letter protein = word organism = dictionary

Proteins As a protein is built, it folds into a structure. There are many levels to protein this process. Some proteins are just structural, while others (enzymes) will perform functions

Basic translation steps mRNA moves from nucleus to a ribosome. aa are transported to the ribosomes by tRNA molecules. The anticodon site on the tRNA is complementary & pairs with the mRNA codon. Terminal end attaches to aa. The aa on the tRNA matches the codon on the mRNA to ensure correct sequencing of aa assembled.

Protein Assembly: Begins when ribosome attaches to the start codon (AUG) on mRNA. The start codon pairs with the anticodon (UAC) on tRNA which carries the aa methionine. (may be removed later) The ribosome moves along the mRNA pairing up the codons w/ anticodons on tRNA

Protein Assembly con’t: The pairing of [codon – anticodon] causes the specific aa to create a covalent bond to the previous aa called a __________ bond. As the ribosome moves along the mRNA, a polypeptide chain is created. A stop codon is reached and the ribosome is released from mRNA & polypeptide chain is complete. Several ribosomes can translate from the same mRNA simultaneously. Polypeptide chain represents proteins primary structure and will fold & associate with other polypeptide chains.

Protein Synthesis Song Protein Synthesis Song-Waltz of the Ribosomes

Ribosome translating DNA to a protein

Web Sites to visit: Animation of Translation http://www.wiley.com/legacy/college/boyer/0470003790/animations/translation/translation.htm   http://www.zerobio.com/translate.htm http://www.pbs.org/wgbh/aso/tryit/dna/ (Click on DNA workshop activity)