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NUCLEIC ACIDS AND PROTEIN SYNTHESIS DNA IS THE GENETIC CODE: The genetic code is: ________________________________________________ _____________________________________________________________________ EVIDENCE OF DNA AS THE GENETIC CODE: EXPERIMENTS: 1. (1928) Griffith: _____________________________________ 2. (1952) Hershey & Chase: __________________________________ SUMMARY OF GRIFFITH’S EXPERIMENT: Isolated 2 different strains of pneumonia bacteria (disease causing strain and a harmless strain) from mice and injected into mice Griffith cultured disease causing cells, heated the cells to kill them, and injected mice…mice lived He mixed heat-killed disease causing cells with harmless bacteria, and injected mice…mice developed pneumonia and died Heat-killed bacteria passed their disease-causing ability to harmless strain - called this transformation (one strain had been transformed into another) Griffith’s Hypothesis: a factor was transferred from the heat-killed bacteria to harmless bacteria, and since the ability to cause disease was inherited by the transformed bacteria’s offspring, that factor might be a gene SUMMARY OF HERSHEY & CHASE EXPERIMENT: BACTERIOPHAGE: _____________________________________________________ ________________________________________________________________________ o Hershey/Chase wanted to determined which part of the bacteriophage (the protein coat or nucleic acid core) entered the infected cell o They thought this would allow them to learn whether genes are made of protein or DNA o They grew viruses in cultures containing 32P and 35S o If 35S was found in the bacteria, then protein coat was injected into the bacteria o If 32P was found in bacteria, then DNA had been injected o Results: all radioactivity in bacteria was from 32P o Conclusion: the genetic material of bacteriophage was DNA, not protein DNA STRUCTURE & FUNCTION THE BUILDING BLOCKS OF DNA ( _____________________________________) 1. DNA is a polymer made up of _______________________________________. a) A nucleotide monomer has 3 parts: 1. A 5-C sugar called ________________________________ oDeoxyribose is __________________, b/c it has 5 carbons 2. A ________________________ group 3. 1 of 4 _______________________________ 2. Four different nitrogenous bases can be found in DNA. These bases can be of two forms, either ____________________ or _________________________. a) Purines (bigger bases - 2 rings): ____________________ & ________________ b) Pyrimidines (smaller bases - 1 ring): ________________ & ________________ HINT: GA is a bigger state than CT - bigger state=bigger bases! 3. Nucleotides join together when _____________________________form between the sugars and phosphates of the nucleotides. This forms the sugar-phosphate “backbone” of the DNA molecule. 4. The bases are bonded to the __________________________in the nucleotides. 5. Bases of nucleotides are held to each other by weak _____________________ bonds. Evidence of DNA’s Structure: Evidence #1. (1950) Franklin & Wilkins: X-Ray Crystallography (Helical Shape) Evidece #2. (1953) Watson & Crick: Double Helix Model & Complementary Base Pairing DNA STRUCTURE & FUNCTION (cont.) DNA Structure: 1. DNA is a _______________________________________. There are ______ strands of DNA in each double helix. Each strand has a backbone of alternating______________________________. Backbones of sugar and phosphate are connected to each other at the bases by _______________________________________________. 2. Complementary base pairing is the specific attraction between certain bases. ______________ (G and A) bond to _____________________________ (C and T). Adenine (A) always bonds to _____________________ Cytosine (C) always bonds to _____________________ CHARGAFF’S RULE: the # of _____________________ = # of thymine the # of _____________________= # of guanine 3. Therefore, the bases of _____________________________determine the _______________________________________. Hmmm…… If you have a DNA molecule with 120 bases, and 20 of those bases are adenine, how many thymine, guanine and cytosine are there? __________ thymine ___________ cytosine ___________ guanine What is the matching strand? AATGCGATA _________________________________ CHROMOSOMES AND DNA REPLICATION DNA and Chromosomes: Prokaryotic cells o DNA molecules are located in the _______________________________ o most have a _________________________________molecule that contains nearly all of the cell’s genetic info Eukaryotic Cells o DNA is in the _____________________in the form of _________________________ o Eukaryotic chromosomes contain _________ and ___________________, packed together to form _____________________________ Chromatin consists of DNA tightly coiled around proteins called _______________________________ DNA and histones together form ___________________________ Nucleosomes can fold huge lengths of DNA into the nucleus (the nucleus contains more than 1 meter of DNA!) DNA Replication: Structure of DNA relates to its function o Each strand of DNA double helix has info needed to create the other half because of __________________________________________ o Model of replication is __________________________________because ____________________________________________________________ ____________________________________________________________ Eukaryotes o DNA replication occurs at _______________________________and proceeds in _______________________________directions until each chromosome is replicated o Replication forks: _____________________________________________ _______________________________________________________________ Prokaryotes o Replication begins at a _____________________________and proceeds in ________________________directions until entire chromosomes is replicated Steps of DNA Replication: 1. Enzyme __________________________“unzips” the strands of the double helix by breaking the hydrogen bonds that hold the bases together. 2. The separated strands of DNA serve as ________________________from which new copies can be made. 3. The now exposed bases are free to match up with their complementary bases to form another strand of DNA. 4. _______________________________________adds new complementary DNA nucleotides to the template strand. DNA strands have a 3’ end and a 5’ end Primed numbers refer to the carbon atoms at the end - 3’ end C is bonded to an OH and 5’ end carbon is bonded to a phosphate group DNA polymerase adds nucleotides to the _____________________ end ONLY 5. _________________________________________links new pieces together RNA RNA stands for ____________________________________________________ o Monomers: RNA nucleotides. o Structural Differences between DNA and RNA: Sugar: __________________________ Bases: Pyrimidines: __________________and cytosine (C) Purines: adenine (A), and guanine (G) o Shape: _____________________________________________ DNA vs RNA DNA SUGAR SHAPE RNA BASES Types of RNA: 1. Messenger RNA (mRNA): _______________________________________________ ________________________________________________________________________ 2. Transfer RNA (tRNA): _________________________________________________ ________________________________________________________________________ 3. Ribosomal RNA (rRNA a.k.a. ribosome): __________________________________ ________________________________________________________________________ TRANSCRIPTION Definition: Transcription is ________________________________________________ ________________________________________________________________________ ________________________________________________________________________ Location: in cell ___________________________ Purpose: _______________________________________________________________ _______________________________________________________________________ This is done so that mRNA can leave the nucleus and take these instructions to the _______________________ where it will be used to make ________________________ Summary: The bases of DNA are grouped into 3 letter “words”. These words are called ________________________________ ____________________________________ (enzyme) attaches to DNA and separates the DNA strands. The RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of mRNA. o RNA polymerase only binds to DNA in an area called the ______________________ region, which has a specific base sequence. The promoters _______________________________________________ ___________________________________________________________ mRNA bases are floating around in the nucleus and now can match up with their complementary DNA base (A-U and C-G) with the help of RNA Polymerase. A strand of mRNA is made which _____________________________________ _______________________________________carrying DNA’s “instructions”. TRANSCRIPTION: RNA Editing RNA is produced by copying ______________________________ DNA contains sequences of nucleotides called ____________________ that are not involved in coding for proteins ____________________________ are DNA sequences that code for proteins When RNA is formed, both __________________________________ are copied from DNA, but the introns are _________________________________while it is still in the nucleus The remaining _____________________ are then joined back together to form ________________________________________ PROTEIN SYNTHESIS Definiton: Protein Synthesis a.k.a. ______________________________is the decoding of a strand of _______________________into a strand of _______________________ (protein) Location: on the ____________________________________ in the cytoplasm of cells. Purpose: to use the info (DNA’s instructions) found in __________________________ to link together ___________________________ to make ________________________ Summary: The bases of mRNA are grouped into 3 letter “words” too. These words are called _____________________________ Each codon has a specific meaning, which is understood by the ribosome. Each codon represents an_______________________________. (Codons code for amino acids) As each codon of the mRNA moves through the ribosome, the ribosome decodes the codon’s “meaning” and determines the amino acids that it represents. These amino acids are then brought to the ribosome by _________________________ tRNA matches up to the codons using an ____________________________ Anticodons are 3 bases on _____________________ – anticodons match with ________________________ These amino acids connect to one another through _____________________ bonds, forming a long chain called a _________________________ or a protein. o Stop codons: codons on the MRNA that ___________________________ _______________________________________________________________ TYING IT ALL TOGETHER: ___________________codes for the _________________________ that make up a ________________________________that determines a ______________________! MUTATIONS A _____________________________is any change (error) in the nucleotide sequence. It may involve a part of the chromosome, or only a single base pair. Mutations are caused by ___________________________, physical or chemical agents that cause mutations. There are two types of mutations: ____________________________ Mutations ____________________________ Mutations CHROMOSOMAL MUTATIONS Chromosomal mutations: ________________________________________________ ________________________________________________________________________ There are four types of chromosomal mutations: 1. Deletions: _____________________________________________________ _________________________________________________________________ 2. Duplications: __________________________________________________ _________________________________________________________________ 3. Inversions: ____________________________________________________ _________________________________________________________________ 4. Translocations: _________________________________________________ __________________________________________________________________ GENE MUTATIONS Gene mutations: ________________________________________________________ _______________________________________________________________________ There are two types of gene mutations: 1. Base Substitutions Point Mutations Silent Mutations 2. Base Insertions & Deletions Frameshift Mutations BASE SUBSTITUTIONS Point Mutations-one base is replaced with another base that changes the _________________in a way that ____________________________ the amino acid. EX: DNA: AAT CGA mRNA: UUA GCU Amino Acids: Leucine Alanine Mutated DNA: AAT TGA mRNA: UUA ACU Amino Acids: Leucine Threonine DISEASES: CYSTIC FIBROSIS, HUNTINGTONS Silent Mutations-one base is replaced with another base that changes the mRNA codon ________________________________________________________________________ EX: DNA: AAT CGA mRNA: UUA GCU Amino Acids: Leucine Alanine Mutated DNA: AAC CGA mRNA: UUG GCU Amino Acids: Leucine Alanine BASE INSERTIONS AND DELETIONS: Frameshift Mutations-the inserting or deleting of one or more bases that ___________ ________________________________________________________________________ EX: DNA: AAT CGA mRNA: UUA GCU Amino Acids: Leucine Alanine Mutated DNA: AAT TCG A mRNA: UUA AGC U Amino Acids: Leucine Serine DISEASES: SICKLE CELL ANEMIA GENE REGULATION A fraction of genes in a cell are expressed at any given time An Example of Gene Regulation in Prokaryotes In E. Coli, there is a cluster of 3 genes that are turned on/off together Operon: _______________________________________________________________ These genes must be on for the bacterium to use the sugar lactose as food Called the ______________ operon Lac operon genes code for proteins that ______________________________________ of bacterium and break the lactose into _________________________and ______________________________ Operator: ______________________________________________________________ ________________________________________________________________________ Repressor: molecule that _________________________ genes by preventing _____________________________from binding, therefore not allowing ______________________________ to occur o So, if _________________________is present, repressor binds to operator and blocks transcription by preventing RNA polymerase from binding. o When lactose is present, it binds to the repressor, removes it, and then transcription can occur! Eukaryotic Gene Regulation Eukaryotic gene regulation is more complex than prokaryotic “TATA” box o o Short region of DNA containing the sequence TATATA or TATAAA that appears next to many promoter regions in eukaryotic genes Believed to help position RNA polymerase by marking point just before where transcription begins Hox genes o Controls the differentiation of cells and tissues in the embryo