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Griffith’s Experiments Study suggested that DNA was probably the genetic material http://nortonbooks.com/college/biology/ani mations/ch12a01.htm http://www1.teachertube.com/viewVideo.ph p?video_id=113347&title=History_of_DNA Hershey and Chase Experiments Radioactive bacteria! 32P was injected into Hershey & Chase proved that DNA was the cell’s genetic material! http://highered.mcgrawhill.com/sites/0072437316/student_view0/chapt er14/animations.html Protein coat labeled with 35S Hershey & Chase T2 bacteriophages are labeled with radioactive isotopes S vs. P bacteriophages infect bacterial cells bacterial cells are agitated to remove viral protein coats Which radioactive marker is found inside the cell? Which molecule carries viral genetic info? DNA labeled with 32P 35S radioactivity found in the medium 32P radioactivity found in the bacterial cells Chargaff Discovered that amts of Adenine = Thymine, and Guanine = Cytosine James Watson and Francis Crick Double helix …..held together by hydrogen bonds • • • • • DNA 1. Sugar deoxyribose 2. Phosphate 3. Nitrogen base -thymine RNA 1. Sugar ribose 2. Phosphate 3. Nitrogen base -uracil Base Pairing DNA Thymine (T) – Adenine (A) PYRIMIDINE PURINE Guanine (G) – Cytosine (C) PURINE T A G C PYRIMIDINE Weak hydrogen bonds T or C A or G DNA 5 O 3 3 P 5 O O C G 1 P 5 3 2 4 4 P 5 P 2 3 1 O T A 3 O 3 5 O 5 P P9 Base Pairing RNA Uracil (U) – Adenine (A) PYRIMIDINE PURINE Guanine (G) – Cytosine (C) PURINE PYRIMIDINE U A G C 1. DNA unzips (hydrogen bonds between the nitrogen bases are broken by enzymes). 2. Free nucleotides pair with exposed bases. DNA Polymerase bonds the nucleotides together. 3. Two identical double stranded DNA molecules are formed. (ClassZone) http://nortonbooks.com/college/biology/ animations/ch12a04.htm • 1. RNA is single stranded DNA is double • 2. RNA can leave the nucleus and enter the cytoplasm DNA can not. • 3. RNA has the sugar ribose, DNA has the sugar deoxyribose • 4. RNA- uracil, DNA- thymine http://highered.mcgrawhill.com/sites/0072437316/student_view0/chapter1 4/animations.html • 1. mRNA: messenger RNA, a copy of DNA from the nucleus. • Reads DNA and copies it into RNA T A DNA A U C G RNA • 2. rRNA : ribosomal RNA, found on the ribosomes and functions in attaching to mRNA to assemble the correct order of amino acids. Binds to mRNA Binds to tRNA • 3. tRNA : transfer RNA, located in cytoplasm • it picks up amino acids and like a factory worker it puts the correct amino acid in place to build a protein. • Each tRNA has an anticodon on it that corresponds to the mRNA codon read off of the DNA. A U Serine (amino acid) tRNA G U C A mRNA I. Transcription: 1. DNA unzips with the help of RNA Polymerase http://www.dnatube.com/video/3450/DNATranscription http://w 2. mRNA reads the DNA, RNA Polymerase ww.dnat ube.com bonds the RNA nucleotides together. /video/3 446/Bio Rap3. mRNA breaks off and leaves the DNAnucleus and travels to the ribosomes in theReplicati on-andcytoplasm. ProteinSynthesi DNA strand TAC GCT TAG TTA ACT s-with-amRNA strand AUG CGA AUC AAU UGA Beat II. Translation: 1. mRNA attaches to ribosome. The ribosome reads 1 codon at a time. The process begins with a start codon. 2. tRNA with an amino acid finds its anticodon complement on mRNA’s codon. mRNA : AUG UUU CCC CGA - codons tRNA : UAC AAA GGG GCU - anticodons 3. Ribosomes continue to read the codons and another tRNA attaches leaving another amino acid. 4. Step 3 continues until the whole strand of mRNA is read, when the stop codon is reached the protein is completed. http://highered.mcgrawhill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::5 35::/sites/dl/free/0072437316/120077/micro06.s wf::Protein Synthesis http://www.biotopics.co.uk/genes/translation.html Prokaryotic Transcription: Operon – a region of DNA that contains a promoter, operator, and structural genes. 1. Promoter – DNA segment that allows a gene to be transcribed, RNA Polymerase binding site. 2. Operator – DNA segment that turns a gene “on” or “off” *The lac operon was one of the earliest exps of gene regulation in bacteria Lactose absent http://pages.cs am.montclair.e du/~smalley/L acOperon.mo v Lactose present http://wwwclass.unl.edu/biochem/gp2/m_biol ogy/animation/gene/gene_a2.html http://www.biologycorner.com/bio4/notes/gene-expression.php – The lac operon is “off” when lactose is not present. – The lac operon is “on” when lactose is present. Eukaryotic Transcription: *Transcription is controlled by regulatory DNA sequences and protein transcription factors. – Most eukaryotes have a TATA box promoter. – Enhancers and silencers speed up or slow down the rate of transcription. 3 Steps 1. Addition of the cap 2. Addition of the tail 3. Removal of introns with the splicing together of exons Exons - code for parts of the protein Introns – nucleotides that occur between exons http://nortonbooks.com/college/biology/ani mations/ch13a05.htm http://nortonbooks.com/college/biology/ani mations/ch12a05.htm Gene mutations: a change in the sequence of nucleotides within a gene. When do mutations occur? - most often during DNA replication. Different Types (pg 253 Fig 8.20) 1. Point Mutations- 1 nucleotide is changed to another, thus coding for a different amino acid. Single base pair substitution. 2. Frameshift mutations- add or delete a nucleotide to cause the other bases to move up or down the DNA molecule. http://nortonbooks.com/college/biology/ani mations/ch13a08.htm (Change in chromosome structure) Different Kinds 1. Deletion: when part of a chromosome is left out. 2. Insertion: part of a chromosome breaks off and inserts into another causing a duplication in the other chromosome. 3. Inversion: genes break off and are reinserted backwards 4. Translocation: genes break off and add to a different chromosome.(pg 253) Causes: mutations are random events. Most often though environmental factors play a huge role in gene mutations Read p254-255 and answer Apply Q on p254, and Summarize Q on p255 http://www.teachersdomain.org/asset/lsps0 7_vid_rnai/ *Many chromosome mutations result when chromosomes fail to separate properly during meiosis. Nondisjunction - occurs when homologous chromosomes or sister chromatids fail to separate. Causes: Down syndrome, Turners syndrome, Klinefelters syndrome, cancer, etc. http://www.biology.iupui.edu/biocourses/N100/2k2human csomaldisorders.html http://www.pbs.org/wgbh/nova/body/rnai.ht ml NOVA video (RNAi) copyright cmassengale • DNA is made up of a long chain of nucleotides. • Each nucleotide has three parts. – a phosphate group – a deoxyribose sugar – a nitrogen-containing base phosphate group nitrogen-containing base http://www.sumanasinc.com/webcontent/ animations/molecularbiology.html deoxyribose (sugar)