Genetics – Microbiology Test Questions – Flashcards
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| Heredity |
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| the transmission of genetic information from an organism to its progeny (offspring). |
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| Chromosomes |
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| a circular (prokaryotes) or linear (eukaryotes) molecule of DNA and proteins that contains genes |
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DNA structure |
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–arranged in a double helix –contains deoxyribose sugar and phosphate backbone –composed of nucleotides (A, T, C, G) –Antiparallel strand orientation –Strands are complementary |
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| nucleotides |
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DNA- ATCG RNA-AUCG |
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Genes |
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| a segment of DNA specifying a particular product (usually a protein) |
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Alleles |
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| different variations of the same gene |
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| Mutation |
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| permanent alteration in DNA |
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Genetic information transfer
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the Central Dogma of molecular biology [image] |
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| Replication |
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| DNA synthesis; existing DNA used as a template to make new DNA |
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Transcription
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| RNA synthesis; existing DNA (genes) used as a template to make RNA (rRNA, mRNA, and tRNA). |
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| Translation |
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| Protein synthesis; RNA molecules are used to form proteins from amino acids |
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| What Direction does DNA replication take place? |
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| Always occurs in a 5’ to 3’ direction |
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| What direction does the two replication forks move? |
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| Bidirectionally (progress in two directions simutaneously) |
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| What are required enzymes for DNA replication? |
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Gyrase Helicase DNA polymerase Ligase |
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Gyrase
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| unwinds the DNA double helix. |
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Helicase |
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| “unzips” the two strands of DNA (breaking of hydrogen bonds that hold the strands together). |
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| DNA polymerase |
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| adds nucleotides to synthesize a new DNA strand (daughter strand) from the template strand (parental strand) |
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Ligase |
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| seals the “nick” where replication forks meet (adds the final phosphodiester bond). |
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Leading strand synthesis |
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| replication is continuous because the replication fork is already moving in a 5’ à 3’ direction for the leading strand. |
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Lagging strand synthesis |
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| replication is discontinuous (via the synthesis of Okazaki fragments) because the replication fork is moving in a 3’ à 5’ direction for the lagging strand, which does not work for DNA polymerase. |
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RNA Synthesis- Transcription is catalyzed by this |
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RNA Polymerase |
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Promoter sequences |
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| site on a gene where RNA polymerase binds and begins transcription |
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3 RNA types |
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ribosomal RNA (rRNA) messenger RNA (mRNA) transfer RNA (tRNA) |
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ribosomal RNA (rRNA): |
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| component of ribosomes |
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messenger RNA (mRNA) |
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| template for protein synthesis |
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transfer RNA (tRNA) |
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| brings amino acids to the ribosome for the growing polypeptide |
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Eukaryotic
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–genes contain introns that are excised –RNA synthesis in nucleus; protein synthesis in cytoplasm |
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Prokaryotic |
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–no introns in genes –RNA and protein are synthesized in the cytoplasm |
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mRNA codons |
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| determine the amino acid sequence of a protein. |
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tRNA anticodons – |
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| complementary to the codons of mRNA |
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A tRNA carrying an amino acid |
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| is “charged”. An uncharged tRNA is not bound to an amino acid. |
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rRNA |
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| component of ribosomes, which catalyze protein synthesis. |
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Ribosomes: Small |
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(30S) subunit •composed of 16S rRNA and 21 proteins |
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| Ribosomes Large |
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(50S) subunit •composed of 5S rRNA, 23S rRNA, and 31 proteins |
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Enzyme Repression |
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| enzymes to metabolize a substrate are not made if the substrate is not present |
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Enzyme Induction |
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| – enzymes to metabolize a substrate are made if the substrate is present. |
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Point mutations |
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Missense
Nonsense
Silent |
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Missense: |
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| base change results in a new codon that dictates a different amino acid. |
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Nonsense |
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| : base change results in a stop codon that terminates translation. |
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Silent |
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| : base change results in a new codon that does not change the amino acid. |
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Frameshift |
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| caused by the deletion (–1) or insertion (+1) of a base. |
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| Causes of DNA mutations |
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Spontaneous errors during DNA replication
Chemical mutagens –base analogs – mimic nitrogenous bases –acridine derivatives – cause frameshifts
UV Radiation –causes thymine dimers |
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| Start Codon |
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| AUG |
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| Stop Codon |
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UAA UAG |
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| Name three types of rRNA |
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16S 23S 5S |
