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Micro Unit 6 of 14
Microbiology Study Guide for the CLEP Exam (Genetics)
| Question | Answer |
|---|---|
| What is transcription? | The process by which RNA polymerase uses a DNA template to produce mRNA. |
| What is an operon? | Two or more genes in a bacterial chromosone that are transcribed into one mRNA molecule. Eukaryotic cells do not have operons |
| What is translation? | The process of rRNAs translating the mRNA codons into protiens by polyymerizing the correct amino acids in the correct order. |
| What is the function of "RNA polymerase"? | Used to produce the RNA copy of each gene |
| What is the function of "mRNA"? | A template for the coded genetic information in DNA to be translated into protien |
| What is the function of "ribosomes" | Enzymes that carry out the process of translation |
| What is the function of "codon" | A nucleotide triplet that codes for a specific amino acid |
| What si coupled transcription and translation? | Coupled transcription and translation is the simultaneous synthesis of RNA and protien that occurs in the cytoplasm of prokaryotes |
| What does a triplet of bases encode? | Each triplet codon in mRNA codes for one amino acid |
| How did griffith demonstrate a gene transfer? | He showed that capsular production could be restored to a capsular mutant from dead, wild-type bacteria |
| How did Avery show that genes are made of DNA? | He and his coworkers showed that the bacterial substance that caused transformation was DNase sensative. This provided strong evidence that transferal of DNA rather than protien or RNA was neccessary for capsule production |
| What type of gene transfer mechanism did Hershey and Chase use to confirm that DNA is the genetic material? | They used transduction to confirm that DNA is the genetic material |
| Define "gene" | The DNA coding material for a single protien |
| Define "choromosome" | A large circular molecule of several million bases of DNA that contains cellular genes |
| Define "genome" | The collection of all the cells in a gene |
| Define "complementary DNA" | DNA that will base pair with another DNA molecule because it has A in place of every T, C in place of every G of the molecule |
| How many genes might there be in the average bacterium? | about five thousand |
| How many genes might there be in a human cell? | about fifty thousand |
| What cells have diploid or haploid genomes? | Prokaryotic cells have haploid genomes; eukaryotic cells have diploid genomes |
| What must happen to the genetic material when cell division occurs? | the genome must be duplicated |
| Where does DNA synthesis begin? | at the origin of replication |
| What is produced by DNA replication? | two double-stranded DNA molecules identical to the starting DNA are produced during DNA replication |
| How does DNA proofread? | DNA proofreads through DNA polymerase, which checks to see if the newly added nucleotides are complementary to the template. If they are not complementary, DNA ploymerase removes and replaces them with a new nucleotide |
| Are human viruses harmful or beneficial? | Both. What a virus causes damage to the host, it's harmful. When a virus is used by gene therapy to repair a genetic defect, it's beneficial |
| What is a viral vector? | A viral vector is a virus used by gene therapy to deliver a gene with proper activity to host cells that need the gene |
| When do bacteria normally regulate gene expression? | During transcription |
| How is lac operon induced? | Lactose combines with the lac repressor to inactivate it. RNA polymerase can then bind to the promoter and transcribe the lac operon |
| How is the tryptophan operon repressed? | Tryptophan binds to the trp operon aporepressor to form an active complex, which binds to the trp operator and prevents RNA polymerase binding and transcription |
| Describe feedback inhibition | feedback inhibition is associated with repressible operons where the end product of the operon pathway makes a complex with the aporepressor to inhibit transcription |
| Give two ways that inducible and repressible expression control differs | Inducible systems turn on expression while repessible systems turn them off. Repressible systems have fine control over how much expression occurs. |
| What is the function of proteases? | to rid the cell of unwanted protien |
| List three things that can cause mutation | 1. A mistake in the DNA-dependent polymerase 2. Chemicals found in the environment 3. ultraviolet rays from the sun and tanning lights |
| What process causes spontaneous genetic change? | Mutation |
| What is the heritable change in the base sequence of DNA called? | Mutation |
| Define "Nonsense mutation" | Gives rise to a stop codon in the middle of the gene so that translation stops before it's complete |
| Define "Frame-shift deletion" | Indicates that nucleotides, perhaps ane or two (not three), have been deleted from a gene so that downstream codones are no longer in register. |
| Give an example of phenotypic and genotypic changes in the lac operon | A mutation in the lac operon, the 3 structural genes or the control promotor or operator regions could result in the cell becoming phenotypically lactose. If we knew that the mutation rendered the lacZ nonfunctional it would be a lacZ genotype |
| Which change, phenotypic or genotypic, would produce a lactose auxotroph? | both |
| How might regulatory mutations in the lac operator or promoter affect cell function? | a mutant lac operator would not bind the repressor, so the lactose operon would be expressed constitutively. a mutant lac promoter would be unable to bind RNA polymerase so no transcription would be possible. |
| What does the "Ames" test show? | This test shows whether test chemicals increase the frequency of mutations. If the frequency increases, the chemical under question is called mutagen or even a carcinogen. |
| In which type of transfer does a sex pilus form a bridge between two bacteria? | conjunction |
| What is the difference in location of the F-factor in an F+ cell and an Hfr cell? | The F-factor of an F+ cell resides in the extra-chromosomal plasmid; the F-factor of an Hfr cell integrates into and becomes part of the bacterial chromosome. |
| What type of gene transfer transports naked DNA through a cell membrane? | Transformation transports naked DNA through a cell membrane |
| What type of gene transfer is mediated by a bacteriophage? | Transduction |
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