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47 Cards in this Set
- Front
- Back
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Chemical Properties of DNA |
Deoxyribose sugar attached to single phosphate group (negative) Consists of 4 bases: Adenine (A), Thymine (T), Guanine (G) and Cytosine (C) A & T = 2 H bonds C & G = 3 H bonds C & T = Pyrimidines A & G = Purines |
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Semi-Conservative Replication (Who experimented with it and What is it?) |
- Meselson and Stahl - experiment occurred in 1958 - radio labelled nitrogen and E-coli bacteria to prove DNA Replication was semi-conservative Semi-conservative: each DNA molecule is composed of one old strand and one new strand |
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DNA Helicase |
- Used to break H-bonds between nitrogen bases, allowing DNA double helix to unwind and separate |
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Single Stranded Binding Proteins (SSBS) |
- Prevents two separated DNA strands from re-annealing |
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DNA Gyrase |
- enzyme that relieves tension produced from unwinding of DNA |
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DNA Polymerase III (3) |
Leading Strand: - adds DNA nucleotides to the RNA primer Lagging Strand: - builds short sequence of DNA off RNA primers called Okazaki fragments DNA Repair: if base pairs are mismatched, it can back up and replace the incorrect base |
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RNA Primer |
-short strand of RNA (starting point for DNA synthesis) |
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RNA primase |
- enzyme which builds and binds RNA primers to DNA |
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Leading Strand |
- goes towards replication fork - replicated continuously in 3'-5' direction - happens quickly |
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Lagging Strand |
- goes away from replication fork - replicated/built in short segments in 5'-3' direction - takes longer than leading strand |
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Okazaki Fragments |
- short fragments of DNA |
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Dna Polymerase I (1) |
- removes RNA primers once used and replaces them with proper DNA sequences - repair complex along with Poly II(2) - proofreads sequence |
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DNA Ligase |
- joins okazaki fragments together - forms one long strand by creation of phosphodiester bonds |
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DNA Polymerase II (2) |
DNA Repair: - repair complex along with DNA Poly I (1) - corrects error by removing incorrect base |
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Central Dogma of DNA |
DNA is too valuable to leave nucleus, so in order to direct formation of proteins it must be TRANSCRIBED into DNA, in which it is then sent out into the cytoplasm where it is TRANSLATED into protein. |
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DNA vs RNA |
DNA: - deoxyribose sugar - thymine (T) base - double stranded - found in nucleus RNA: - ribose sugar - Uracil (U) base - single stranded - found in nucleus and cytoplasm |
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RNA importance and 3 types |
Importance: Protein Synthesis (required to make proteins) - one of the three major biological macromolecules that are essential for all known forms of life ?? 3 types: 1 - mRNA/messenger (copy of DNA) 2 - tRNA/transfer (brings correct amino acids into ribosome) 3 - rRNA/ribosomal (structural part of ribosome) |
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What happens during Transcription? |
Initiation:
- RNA polymerase binds to promoter region and opens up double helix - region is filled with multiple A & T base pairs due to double H bond being easier to break Elongation: - Building of mRNA strand in 3'-5' direction - similar to DNA replication except 1) no primers and 2) only one strand of DNA is used - Template strand is used and is complementary to mRNA - Coding strand is unused strand is identical to mRNA (except for U) Termination: - RNA polymerase continues until it reaches a termination sequence (unknown) - mRNA dissociates - RNA poly is free to transcribe another gene |
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3 post-transcriptional Modifications |
1) 5' Cap Added - 7 G's are added to beginning of mRNA strand to prevent digestion in cytoplasm 2) Poly A Tail - poly-A polymerase adds 50-250 Adenine bases to tail of mRNA to prevent degradation 3) Introns cut out - Introns are non-coding regions (exons are coding regions) and if transcribed the protein is unable to fold properly. Splicesomes (combo of RNA and protein) remove introns and bind exons together. SnRP's bind to introns and signal removal. |
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What happens during Translation? |
Initiation: - mRNA leaves nucleus and enters cytoplasm - Ribosome recognizes 5' cap and binds to mRNA - Riboome begins translating starting with start codon (AUG) 3 sites for binding of tRNA: A(acceptor) site - tRNA brings in new amino acid P(peptide) site - peptide bonds form between new amino acid E(exit) site - tRNA leaves ribosome Elongation: - tRNA transfers new amino acid to A site - tRNA leaves E site - tRNA is recycled by aminoacyl-tRNA synthetase, in which it then attaches new corresponding amino acid to tRNA Termination: - 1 stop codon is reached (3 stop codons - UGA, UAG, UAA) - no corresponding tRNA for stop codon - 2 ribosome subunits dissociate from mRNA - polypeptide chain is released and modified |
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How does eukaryotic gene control work and What is its purpose? |
How it Works: - turns on or off specific genes depending on organisms needs Purpose: Conserves energy when genes are not required/needed |
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Prokaryotic LAC and TRP Operons |
LAC Operon: - bacterial cells use neg. regulation to block transcription and translation of Beta-galactose gene if lactose is not present TRP Operon: - codes for production of tryptophan - expressed when |
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Point Mutations and the 4 types |
Point Mutation: change of a single nucleotide within a gene 4 types: Insertion - addition of bp or lrg coding region to a DNA sequence Deletion - removal of bp or lrg coding region from a DNA sequence Substitution - replacement of one bp in a DNA sequence by another bp Inversion - two adjacent bp trade places or reversal of DNA sequence |
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Missense Mutation |
- mutation which changes a single amino acid in the coding sequence ex. CCA/GGT replaces TCA/AGT therefore the mRNA strand codon becomes CCA, changing the amino acid from SER to PRO |
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Silent Mutation |
- mutation does not effect amino acid sequence ex. amino acid still remains the same because multiple codons still code for the same amino acid |
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Nonsense mutation |
- mutation results in premature stop codon ex. TGA/ACT replaces TGC/ACG, so instead of resulting in the codon UGC, the stop codon UGA is formed |
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Frameshift mutation |
- shift in reading frame results in multiple missense and/or nonsense effects - usually caused by addition or deletion of one bp ex. **On DNA rep and repair worksheet GAG/CTC results from A/T insert which shifts the reading frame off by one base, altering amino acids |
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Induced mutation |
- mutation caused by environmental factor/agent ex. sunburn due to Sun's UV light |
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Mutagenic agents |
- Environmental agents which directly alter the DNA within a cell ex. most common are Chemical or Radiation |
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Spontaneous mutation |
- mutation caused by error in DNA replication (quality control system is in place to prevent these errors from occurring, but it does not always work). |
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Translocation |
- movement of entire genes of DNA sequences form one chromosome to another (pGLO lab - glowing trait, as well as antibiotic resistance trait was obtained by E-coli bacteria??) |
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Histone |
- Synthesizing proteins in which DNA coils around them |
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Nucleosome |
- 8 histones plus DNA |
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Solenoid |
- 6 nucleosomes coil together - once formed, this solenoid folds into final structure due to super coiling |
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Chromatin |
Chromosomes consisting of mix of protein and DNA |
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Telomeres |
- ends of chromosomes |
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Centromeres |
- section which holds two chromosome strands together (circular) |
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Pseudogenes |
- DNA sequences that appear similar to other genes but are non-functional/cannot be transcribed |
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LINES and SINES |
- two types of pseudogenes |
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Recombiant DNA |
- DNA fragments composed of sequences resulting from two or more sources |
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Restriction Enzymes Use and Purpose |
Use: "molecular scissors" - cut specific point - binds to recognition site and disrupts phosphodiester bonds via hydrolysis - create either blunt (straight) or sticky ends (hang-over) Purpose: Immune system/resistance - come from bacteria - used as an immune system - enzymes prevent viral DNA from entering bacteria through breaking it down/cutting it up as it tries to invade/enter bacteria |
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DNA Ligase and DNA T4 Ligase |
DNA Ligase: - joins cut strands of DNA - works best with sticky ends (tendency to reconnect via H-bonds) - H-bonds are weak so need to restore phosphodiester bonds - done via condensation rxn T4 ligase: - works well to join blunt ends together |
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Why are plasmids useful and what is their purpose in nature? |
Plasmids: small, circular DNA which can exit or enter bacteria Useful: contain genes which code for specific proteins which are used to benefit host bacteria cell Purpose in Nature: -naturally exist in bacteria cells and provide the bacteria with genetic advantages ex. -antibiotic resistant - resistance to toxic metals - breaking down herbicides - breaking down industrial chemicals |
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What is Transformation? |
- introduction of foreign DNA (usually by plasmid/virus) into bacterial cell -cell which receives DNA is said to be "transformed" |
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What is Genetic Engineering? What are its Advantages and Disadvantages? |
Genetic Engineering: The altering of the sequence of DNA molecules Advantages: - Insulin (development of new products - specifically ones which target our health) - Agricultural impact (decrease of frost damage by introducing bacteria which have been engineered to disable crops from forming ice - targets protein that codes for ice to seed and crystallize) - Somatropin (growth hormone used to treat human growth deficiencies, such as dwarfism and aids - helps build muscle). Can also boost milk production in cows but is banned in Canada Disadvantages: - controversy over growth hormone due to its availability to athletes as it is a banned substance in sporting events during international competitions |
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VNTRP's (Variable Number Tandem Repeats) |
- base pair sequences which repeat over and over |
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Transposons |
- DNA sequence that can change its position within a genome - sometimes creating or reversing mutations and altering the cell's genome size. |
