Chapter Nine (quiz six) – Flashcards
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| What must happen to proteins before it is released from the ribosome |
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| It must fold upon itself to achieve its biologically achieve tertiary conformation Posttranslational modifications may be necessary - starting amino acids cut off - cofactors added - join with other proteins to form quaternary levels of structures |
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| Processing gene information in prokaryotes? |
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| - mRNA can assiocate with ribosomes in the cytoplasm as the mRNA is being formed - translation of mRNA into proteins can begin before transcription is complete |
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| What is an operon? |
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| individual mRNA molecules often contain transcripts for several genes. By placing genes with similar functions on the same mRNA, bacteria coordinate the synthesis of these proteins. These clustered genes are referred to as operons. |
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| Eukaryotic mRNA's code for how many proteins? |
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| just one |
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| Can eukaryotic transcription and translation occur at the same time? |
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| nope because the DNA is in the nucleus, it must occur in different compartments |
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| What do eukaryotic DNA often have? |
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| Introns! these must be removed before translation |
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| What make up split genes? |
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| introns and exons |
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| Introns? |
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| sequences of bases that do not code for protein |
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| exons? |
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| coding regions that will be translated into protein |
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| What percent of DNA do introns make up? |
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| 98% |
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| How is the nucleic acid arranged in virus |
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| usually linear but can also be circular |
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| How is the genome arranged in viruses? |
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| usually a single molecules, but can also be segmented into several peices |
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| Info about animal viruses |
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| -viral nucleic acid penetrates the cell -nucleic acid penetrates the cell - the virus instructs the host's machinery to synthesize large numbers of new virus particles - viral mRNA is translated into viral proteins on host cell ribosomes using host tRNA |
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| Inductible operons |
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| the operons is turned on by the substrate of the enzyme for which the structural genes code (positive feedback) |
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| repressible operons |
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| contain genes coding for anabolic enzymes; several genes in a series are turned off by the product synthesized by the enzyme (negative feedback) |
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| An inducible operon is kept "off" by...? |
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| the repressor |
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| What does the substrate act as for an incucible operon? |
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| an inducer! it blocks the action of the repressor, allowing the operon to be "on" |
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| Example of Incucible Operon |
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| lac operon in E.coli |
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| What is the regulator in Lac Opreon |
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| a gene that codes for a protein capable of repressing the operon, which is the repressor |
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| What are the control locus feature of Lac operon |
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| Promoter: recognized by RNA polymerase Operator: a sequence that acts as an on/off switch for transcription |
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| Structural Locus feature in Lac opreon |
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| three genes each coding for a different enzyme needed to catabolize lactose |
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| Co-repressor in repressible operon |
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| excess nutrient serves as this, it is needed to block the action of the operon |
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| Example of repressible operon |
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| Arg operon |
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| phase variation? |
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| through this, the bacterium can induce or repress the expression of a set of genes and change its phenotype -turn on and off particular genes |
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| What is a mutation? |
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| a change in nucleotide sequence (ATCG) |
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| What is a wild-type? |
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| a microorganism that exhibits a natural, non-mutated characteristic |
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| what is a mutant strain? |
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| when a microorganism bears a mutation |
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| Spontaneous mutation |
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| random change in the DNA arising from errors in replication -random |
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| Induced mutation |
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| results from exposure to know mutagens ex: ultraviolet radiation |
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| Two categories of mutagenic agents |
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| chemical or radiation |
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| Two categories of Mutations |
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| point or frameshift |
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| Point mutations |
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| involve addition, deletion or substitution of single bases |
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| Frameshift mutations |
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| when one ot more bases are inserted into or deleted from a newly synthesized DNA strand -changes the reading frame of the mRNA -nearly always results in a nonfunctional protein |
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| Point-mutation submutation: Missense mutation |
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| results in different amino acid |
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| Point-mutation submutation: Nonsense mutation |
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| results in a premature stop codon |
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| Point-mutation submutation: Silent mutation |
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| no effect |
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| Point-mutation submutation: Back-mutation |
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| second mutation corrects effect of first |
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| Random mutation info |
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| mutation are permanent and inheritable most are harmful but some provide adaptive advantages |
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| Recombination |
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| when one bacterium donates DNA to another bacterium |
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| What is the end result of recombination? |
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| a new strain different from both the donor and the original recipient |
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| What are easily exchanged among bacteria |
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| plasmids! |
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| recombinant organism |
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| any organism that contains (and expresses) genes that originated in another organism |
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| Difference between plasmid and chromosomal fragments mode of transmission of genetic material in bacteria |
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| -plasmid can replicate independently of the bacterial chromosomes -chromosomal fragments must integrate themselves into the bacterial chromosome in order to replicate |
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| What are the 3 means of recombination in bacteria |
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| 1. Conjugation 2. transformation 3. transduction |
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| Conjugation-- factors involved |
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| -donor cell with pilus -fertility plasmid in donor -both donor and recipient are alive -bridge forms between cells to transfer DNA |
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| Conjugation-- Direct or indirect? |
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| direct! |
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| Transformation-- factors involved? |
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| -free donor DNA (fragment) -live, competent recipient cell |
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| Transformation-- direct or indirect? |
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| indirect! |
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| Transduction-- factors involved? |
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| -donor is lysed bacteria cell -defective bacteriophage is carrier of donor cell -live recipient cell of same species as donor |
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| Transduction-- direct or indirect? |
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| indirect |
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| What is a pilus? |
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| cytoplamic bridge that lets two cells dock and transfer materials between them |
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| Stains of bacteria containing/and not the f factor |
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| F+ and F- |
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| Resistance Plasmids? |
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| bear genes for resisting antibiotics -can confer multiple resistance to antibiotics to a strain of bacteria |
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| HFR stains |
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| -the f factor is integrated into the chromosome -the copied chromosome will contain the f factor and chromosomal genes - recipient cell is now an Hfr with new henes |
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| Transfermation is what? |
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| capturing DNA from solution - it is nonspecific acceptance of foreign DNA by a bacterial cell |
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| What are competent cells? |
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| they are capable of accepting genetic material (the live cell) |
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| What is generalized transduction? |
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| It involves a lytic bacteriophage -during bacteriophage assembly, some bacterial host DNA is packaged into capsid with viral DNA |
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| What is specialized transduction? |
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| -involves lysogenic bacteriophage transfer of only a few specific genes from one bacterial cell to another by means of a phage |
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| What are transposons? |
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| jumping genes -they move from place to place in the genome, plasmids, and viral genomes -they disrupt the place they land -they mobilize other genes (like antibiotic resistance |
