How Proteins Are Made CHAPTER 12
DNA, genes, chromosomes How does a chemical control so much?
Intro to DNA Video • http://www.youtube.com/watch?v=bVk0twJYL6Y&feature=youtube_gdata_player • http://www.cleanvideosearch.com/media/action/yt/watch?v=qoERVSWKmGk&NR=1&feature=endscreen&edufilter=wlcstv
Section 1 • Vocabulary: • 1. DNA /double helix, • 2. Nucleosome
Griffith’s experiment 1928: transformation • Showed that “something” changed the non virulent bacteria into virulent!
Avery 1944 • To show that it was DNA and not protein that transformed the bacteria…
Hershey and Chase 1952 • Convinced people that DNA not protein contained the genetic material. Radioactive Sulfur found in protein only and radioactive phosphorus, found in DNA only was inserted into bacteria using viruses that infect bacteria called bacteriophages that had been labeled with the radioactive elements. Radioactivity showed the protein remained outside the bacteria and could not cause the transformations!
Alfred Hershey and Martha Chase--Acceptance within scientific community of DNA as genetic material (Video Clip)
Franklin 1952 • Rosalind Franklind and Wilkins X ray diffraction pictures helped determind the shape of DNA
Erwin Chargaff1950 • He found that when he analyze DNA, the amount of Adenine always equaled the amount of Thymine and the amount of Guanine equaled the amount of cytosine.
Erwin Chargaff--DNA is not equal for all species and ratio of bases varies among species (Video Clip)
Watson and Crick 1953 • Determined the basic structure of DNA. Antiparallel sides of deoxyribose sugar and phosphate with nitrogen bases paired A-T and C-G, (with the help of Chargaffs research)
James Watson and Francis Crick--DNA molecule has the form of a double helix (Video Clip)
DNA Structure • Chromatin--Chromosomes and DNA subunits (Video Clip)
Griffith 1928 1. What happened to the normally non-virulent rough bacteria when mixed with the virulent smooth heat killed ones? they became virulent 2. Based on what happened to the bacteria, what was Griffith’s experiment called? the transforming experiment 3. At the end of Griffith’s experiment, did scientists know if DNA or proteins caused the changes? _no Avery 1944 4. Avery attempted to do what? identify if the substance was protein or DNA 5. Did people accept Avery’s results? NO
Hershey and Chase 1952 6. What is a bacteriophage? A virus ______that that infects bacterial cells. 7. Radioactive phosphorous was used to identify DNA because protein_does not contain phosphorous but DNA does. 8. They could then trace the path of the radioactive phosphorous and found that it ended up in the transformed bacterium’s DNA 9. Radioactively labeled Protein did not enter the bacteria at all but remained outside the cell.
10. Which experiments led to the discovery of DNA as the genetic material? • All of them, Griffith, Avery, Hershey and Chase’s were needed to get to the idea that DNA and not Protein was the genetic material. It was ultimately Hershey and Chase’s experiment that demonstrated that it was DNA and not protein that transmitted the genetic material.
Section 2 • DNA replication p 333 • Vocabulary: • 1. Semi conservative replication, • 2. DNA polymerase, • 3. Okazaki fragment
How does DNA replicate? • 1. Before replication can occur, the length of the DNA double helix about to be copied must be unwound. DNA helicase
2. the two strands must be separated, much like the two sides of a zipper, by breaking the weak hydrogen bonds that link the paired bases. • 3. Once the DNA strands have been unwound, they must be held apart to expose the bases so that new nucleotide partners can hydrogen-bond to them.
4. The enzyme DNA polymerase then moves along the exposed DNA strand, joining newly arrived nucleotides into a new DNA strand that is complementary to the template
Animation of replication • http://www.nobel.se/medicine/educational/dna/a/replication/replication_ani.html
DNA replication Video • http://www.youtube.com/watch?v=9mMEKKyXC5E&feature=youtube_gdata_player • http://www.youtube.com/watch?v=zdDkiRw1PdU&feature=youtube_gdata_player • Bozeman on DNA replication • http://www.cleanvideosearch.com/media/action/yt/watch?v=FBmO_rmXxIw&edufilter=wlcstv
DNA Structure • SC.912.L.16.3 Describe the basic process of DNA replication and how it relates to the transmission and conservation of the genetic information 1. What is a nucleotide composed of? Sugar, nitrogen base and a phosphate group 2. What scientist looked at the data that analyzed the amount of guanine equaled the amount of cytosine and the amount of thymine equaled the amount of adenine and what conclusion did he draw from this? Chargaff/ these nitrogen bases must be paired up in the structure. 3. X-ray diffraction was used to help determine what about DNA? the double helix shape 4. Who are the 2 scientists who put all of the info together to describe the structure of DNA? Watson and Crick • Describe the structure of DNA in detail, use a diagram to help. The sides are made up of the sugar deoxy ribose and the phosphate groups bonded covalently together the rungs are the nitrogen bases with cytosine and guanine bonded with hydrogen bonds across from each other and thymine and Adenine across from each other. The entire thing is in a double helix and runs 3’ to 5’ anti parallel. 6. Describe how the DNA is packaged into a chromosome in a eukaryote and compare this to the prokaryotic chromosome._ DNA is in chromosomes in eukaryotic cells which means it is wrapped around proteins called histones into units called nucleosomes to make chromosomes. In the prokaryotic cell the DNA is in a circular strand.
Section 3 DNA, RNA and Protein Vocabulary: 1. mRNA 2. rRNA 3. tRNA 4. Transcription 5. RNA polymerase 6. Intron 7. Exon 8. Codon 9. Translation
Section 4 • Gene regulation and Mutation Vocabulary: • 1. Gene regulation • 2. Operon • 3. Mutation • 4. Mutagen
DNA • Deoxyribo • Nucleic • Acid
Sugar: deoxy ribosePhosphate: H2PO4 • Nitrogen base: • Adenine • Guanine • Thymine • Cytosine
Answers 1. Proteins are chains of linked amino acids that have been folded into compact shapes. Some proteins play important roles as enzymes. Other proteins are structural components of cells and tissues. 2. Ribosomes are structures built of proteins and RNA that serve as assembly sites for protein synthesis.
3. DNA is an extremely long, linear molecule containing many genes; genes are relatively short segments of DNA that code for protein or RNA. 4. DNA is made of two strands of complementary nucleotides and contains the four bases adenine, thymine, cytosine, and guanine. DNA contains the sugar deoxyribose and serves to store the complete set of an organism’s genetic material. 5. In DNA, adenine (A) pairs with thymine (T), and guanine (G) pairs with cytosine (C).
General Vocabulary 1. gene 2. chromosome 3. chromosomal mutation 4. codon 5. double helix 6. frameshift mutation 7. messenger RNA mRNA 8. monosomy 9. mutation 10. nitrogen base 11. nondisjunction 12. point mutation 13. replication 14. ribosomal RNA rRNA 15. transcription 16. transfer RNA tRNA 17. translation 18. trisomy 19. anticodon 20. protein
The instructions for building a protein are found in a gene and are “rewritten”to a molecule of RNA during transcription. The RNA is then “deciphered” during translation
Making a protein • DNA is found in the nucleus. • The proteins are made on a ribosome from amino acids found in the cytoplasm. • The instructions must get from the nucleus to the ribosome…
Start and stop codes on the DNA define where one gene starts and ends. • The DNA has to be un wound and un zipped for this process to work, just like in DNA synthesis. • Some sections of DNA will be used more often then others.
Transcriptionstep 1 • DNA to mRNA • A copy of the instructions found on the DNA is made using messenger RNA. • The job of the mRNA is to take the instructions to the ribosome where the protein can be made!
DNA to mRNA • If the DNA reads… DNA AAT CCT GGG CCC Then what will the complementary m RNA read? Remember that RNA had uracil instead of thymine, but all other nitrogen bases are the same.
transcription • DNA AAT CCT GGG CCC • mRNA UUA GGA CCC GGG • This is called the complementary strand and goes out into the cytoplasm to find a ribosome….
From Genes to Proteins . The RNA is complementary to the gene, and the RNA nucleotides are put together with the help of RNA polymerase. This process is very similar to DNA replication except only one side is copied and with RNA nucleotides instead of DNA. RNA polymerase is the enzyme that helps this reaction occur!
Translation: turning the code into a protein • When the mRNA gets to a ribosome, the 2 parts of the ribosome assemble on top of it.
There is a start code on the mRNA AUG the RNA bases will be read as 3 together (in triplets) from the 5’ to the 3’ direction. Each triplet makes up a codon.
Transfer RNA or tRNA tRNA is the translator – each tRNA molecule carries one of the 20 amino acids attached to its 3’ end. About midway along the sequence of nucleotides in tRNA are 3 bases that are complementary to the codon – this base sequence in tRNA is called the anti-codon.
Ribosomes • Amino acids are physically linked together to form proteins on the ribosomes, which are located throughout the cytoplasm. • Ribosomes are complex structures composed of proteins and rRNA.
The start codon always has the sequence 5’-AUG-3’. • The ribosome subunits will come together at the start codon and a tRNA with the anti-codon 3’-UAC-5’ will enter the ribosome and will H bond with the codon on the mRNA. • This tRNA will be carrying the amino acid methionine (or formylmethionine in Bacteria).