Ch 8 – Microbiology – Flashcards
Unlock all answers in this set
Unlock answersquestion
| genetics |
answer
| -study of the variability and transmission of characteristics -study of genes, how they carry and pass information |
question
| genome |
answer
| all genetic information in a cell including chromosomes and plasmids |
question
| chromosome |
answer
| structure containing DNA that physically carry hereditary information |
question
| plasmid |
answer
| self replicating, gene containing circular piece of DNA |
question
| genotype |
answer
| genetic constitution of the cell, organism, or individual |
question
| phenotpe |
answer
| -observable characteristic -results from expression of genes and environmental factors |
question
| bacterial chromosome |
answer
| -circular molecule of DNA -looped and folded -attached to plasma membrane at one or more points -about 1 mm long -supercoiled (10% of cell volume) |
question
| expression |
answer
| -genetic info is used within a cell to produce proteins needed for the cell to function |
question
| recombination |
answer
| transfer of genetic information between the same generation of cells |
question
| overview of DNA replication (1-5) |
answer
| -one parental ds DNA is converted into 2 ds daughter DNA molecules -one stand acts as a template for the other -Gyrase/Topoisomerase relaxes supercoiling -Helicase unwinds the two parental strands like a zipper -replication fork is the point where replication occurs |
question
| overview of DNA replication (6-10) |
answer
| -DNA polymerase synthesizes a new DNA strand 5' to 3' -the leading strand is oriented 5' to 3' in which a polymerase "reads" the DNA and adds nucleotides continuously -lagging strand is oriented 3' to 5' in which primase "reads" the DNA and adds RNA in short seperated fragements(Okazaki) -primers are removed -DNA ligase joins fragments together |
question
| DNA replication is ... |
answer
| semiconservative |
question
| bacterial DNA replication is... |
answer
| bidirectional |
question
| at completion of bacterial DNA replication, both forks meet and are separated by |
answer
| topoisomerase |
question
| 1 mistake in DNA rep every ____ due to proofreading of_______ |
answer
| 10^10 bases DNA polymerase |
question
| transcription (5) |
answer
| -synthesis of a complementary strand of RNA (mRNA) from DNA -RNA polymerase binds to a promotor on the DNA and initiates transcription -only one of the two DNA strands acts as a template -RNA is synthesize 5' to 3' -transcription stops once RNA polymerase reaches the terminator |
question
| translation |
answer
| -protein synthsis -decoding of nucleotides into amino acids -the sequence of codons (3 nucleotides) on an mRNA molecule determines the sequence of amino acids in the protein |
question
| in prokaryotes transcription/translation |
answer
| -simultaneous -translation can begin before transcription is complete -occur in cytoplasm -start codon is available to ribsomes |
question
| eukaryotes transcription/translation |
answer
| -transciption occurs in nucleus and must be completed before it is sent to cytoplasm -presence of noncoding DNA(introns) between expressed DNA regions (extrons) -introns removed and extrons spliced together |
question
| snRNP |
answer
| remove introns and splice extrons |
question
| regulation of bacterial gene expression |
answer
| -most genes (60-80%) are always turned on /expressed constitutively(enzymes of glycolysis) -expression of other genes is regulated/only expressed when needed (catabolic enzymes/surface proteins) |
question
| repression |
answer
| -mechanisms that inhibits gene expression and decrease synthesis of enzymes usually in response to an excess of surplus |
question
| repressors |
answer
| -regulatory proteins that block the ability of RNA polymerase to initiate transcription |
question
| induction |
answer
| -mechanisms responsible for turning on the expression of a gene |
question
| inducers |
answer
| substances that induce the transcription of genes |
question
| lac operon |
answer
| -genes coding for 3 enzymes involved in lactose uptake and utilization are next to eachother -LacZ, LacY, LacA (structural genes) |
question
| promotor |
answer
| region on DNA where RNA polymerase initiates transcription |
question
| operator |
answer
| -segment of DNA that a repressor or activator binds to |
question
| LacI |
answer
| regulatory gene that codes for a repressor protein |
question
| mutation |
answer
| change in the base sequence of DNA |
question
| mutation could result in |
answer
| -protein misfolded -enzyme less activated/inactivated |
question
| silent mutation |
answer
| -occurs when mutated base is on the 3rd position of the mRNA codon -codes for same amino acid or has same properties (Asp-Glu) |
question
| point mutation/base substitution |
answer
| - a single base is replaced with another base -transition-purine for purine or vv -transversion-purine for pyramidine or vv |
question
| missense |
answer
| base substitution results in a different amino acid |
question
| nonsense |
answer
| base substitution results in a STOP codon |
question
| frameshift |
answer
| -insertion or deletion |
question
| mutations can be... |
answer
| spontaneous or induced by physical or chemical agents |
question
| examples of mutagens |
answer
| -nitrous acid -UV light -radiation -nucleoside analogs |
question
| mutation rate |
answer
| probability that a gene will mutate when a cell divides |
question
| spontaneous mutation rate |
answer
| 10^-9 |
question
| mutagens increase mutation rate |
answer
| 10-1000 fold |
question
| why bacteria used to study mutation |
answer
| -divide rapidly -only one copy of each gene per cell |
question
| positive selection |
answer
| -selection that kills unmutated cells |
question
| negative selection |
answer
| -used to identify mutants that have lost ability to synthesize an amino acid -these mutant cells cannot grow in the absence of that amino acid (auxotroph) |
question
| replica plating technique |
answer
| -using a velvet to transfer colonies to histidine and non histadine plates to identify auxotrophs |
question
| genetic recombination |
answer
| -exchange of genes between 2 DNA molecules |
question
| protein that catalyzes the joining of 2 stands or recom DNA |
answer
| RecA |
question
| mechanisms of Recombination |
answer
| -transformation -conjugation -transduction |
question
| transformation |
answer
| -genes transferred from one bacterium to another as naked DNA -no contact necessary between donor and recipient -could happen naturally or be induced |
question
| mechanism of transformation |
answer
| -DNA fragments bind to exterior of cell -fragmentation of DNA -one DNA is transferred up to cytoplasm, other is degraded |
question
| conjugation |
answer
| -transfer a portion of a donor bacterium chromosome to a recipient -requires direct contact -as the donor replicates its chromosome, the copy is injected into the recipient -only can occur between cells of opposite mating types |
question
| F+ and F- |
answer
| -donor that carries fertility factor (lack Bio- and Met-) -recipient that does not (lacks Thr- and Leu) |
question
| F |
answer
| set of genes originally acquired from a plasmid and now integrated into the bacterial chromosome -established the origin of replication for the chromosome |
question
| modes of conjuation |
answer
| sex pilli mating bridge |
question
| transduction |
answer
| -transfer of bacterial DNA through a virus (bacteriophage) |
question
| types of plasmids |
answer
| -fertility -resistance -col-plasmids -degradative -virulence |
question
| fertility plasmids |
answer
| -capable of conjugation |
question
| resistance plasmids |
answer
| -contain genes that can build resistance against antibiotics or poisons |
question
| col-plasmids |
answer
| contain genes that code for bacteriocins (proteinacious toxins) |
question
| degradative plasmids |
answer
| allow degradation of unusual substance (toluene) |
question
| virulence plasmids |
answer
| turn bacterium into a pathogen |
question
| transposons |
answer
| small segments of DNA that can be moved from one region of DNA to another (often within genes) |
