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Lecture018
MB351Exam3
| Question | Answer |
|---|---|
| What is a mutation? | A heritable change in the genetic material |
| Mutations can be... | neutral, beneficial, or harmful |
| What is a mutagen? | an agent that causes mutations |
| What is a spontaneous mutation? | mutation that occurs in the absence of a mutagen |
| What are some types of mutation? | Base substitution, silent, missense, nonsense, frameshift |
| What is a base substitution mutation? | when there is a change in one base pair (point mutation) |
| What is a silent mutation? | No change in amino acid sequence (no phenotype effect) for example: TAT to TAC still codes for tyrosine |
| What is a missense mutation? | Results in a change in amino acid. There is a possible phenotype change. |
| What is a nonsense mutation? | Introduces stop codon and produces truncated protein. Effect on phenotype very likely. |
| What is a frameshift mutation? | insertion or deletion of one or more nucleotide pairs. Changes codon reading and multiple amino acids. Effect on phenotype very likely. |
| What is the spontaneous mutation rate? | 1 in 10^(-6) per replicated gene |
| How much does mutagens increase mutation rate per replicated gene? | 10^-5 or 10^-3 per replicated gene |
| What are some mutagens? | Chemical mutagens (acridine dyes, base analogs) or radiation (xrays, gamma rays, UV) |
| What sort of enzymes do bacterias have that can prevent mutations? | They can repair damage with photolyases and mucleotide excision repair |
| What is photolyases? | Bacterias use this enzyme to separate dimers |
| What is a nucleotide excision repair? | Bacterias use this enzyme to cut out incorrect bases and fill gaps. |
| What is genetic recombination? | the physical exchange of DNA between genetic elements |
| Why is recombination important? | It can create new combinations of genes even in the absence of mutation |
| Why is both mutation and recombination important to life? | Together, they both fuel the evolutionary process. They provide genetic diversity. |
| What is the process of genetic recombination? | It involves important forms of exchanges with homologous genes "crossing over" |
| When does crossing over occur in recombination? | When two chromosome break and join |
| A complex process of recombination requires how many proteins? | ~25 proteins/enzymes |
| What protein is involved in recombination and catalyzes the joining of the two chromosome strands? | the protein recA |
| What fills in the gaps and ligates in recombination? | DNA polymerase |
| What happens to non-incorporated DNA in recombination? | They are degraded |
| What are the three mechanisms of genetic exchange in prokaryotes? | Transformation, Conjugation, and Transduction |
| What is transformation in prokaryotes? | It is when free DNA that is released from one cell is taken up by another |
| What is conjugation in prokaryotes? | When DNA transfer involves cell-to-cell contact and a conjugative plasmid in the donor cell |
| What is transduction in prokaryotes? | When DNA transfer is mediated by a virus/phage |
| What can happen to an incoming DNA? | It can genetically recombine with the host, degrade by restriction enzymes, or replicate on its own if it has its own plasmid or phage genome |
| What happens in transformation with DNA fragments? | DNA fragments are inserted into a bacteria cell. The cell uptakes the DNA and either there is a stable transformation where the bacterial chromosome integrates with the DNA or degradation occurs and there is an unsuccessful transformation. |
| What happens with a plasmid transformation? | DNA plasmid is inserted into bacterial cell. Cell uptakes the plasmid, and there is a stable transformation even if plasmid is not integrated into the chromosome. |
| What is transformation in general? | A genetic transfer process by which free DNA is incorporated into a recipient cell and brings about genetic change |
| What is a competent cell? | A cell that is able to take up DNA and be transformed |
| Cells can be induced to be competent using what? | Calcium chloride or by electroporation |
| What are plasmids? | *Independently replicating elements *double stranded DNA, can be non-essential genes *Replicated like DNA or by rolling circle |
| True or False: Multiple plasmids per cell can occur. | True. |
| What is a dissimilation plasmid? | It encodes enzymes for catabolism of unusual cpds. |
| What is an R plasmid? | it encodes antibiotic resistance |
| What is virulence plasmids? | Toxin production |
| What is conjugative or F(fertility)plasmids/factor? | they carry genes for sex pili and transfer of plasmid |
| Why are Pseudomona bacterias used to clean oil spills? | They have dissimilation plasmids and are able to degrade oil for their carbon and energy requirements. |
| How does conjugation occur in bacteria? | Through a Sex Pilus and a Mating bridge |
| How does sex pilus occur in bacteria | Sex pilus draws F- cells closer, induces mating bridge to form |
| What is a mating bridge in bacteria? | It is a region of contact between the donor and recipient cells where the DNA is presumably transferred via a pore |
| How does conjugation occur in E. Coli? | Donor cell (F+) has F plasmid, encodes genes to make pilus. Recipient cell (F-) becomes F+ when it receives F plasmid. |
| True or False: Conjugation in E.coli is conservative, donor retains copy of plasmid after transfer | True. |
| True or False: Sometimes the F plasmid recombines with the chromosome to become a Gfr cell | False: It becomes an Hfr cell (High frequency of recombination) |
| What happens through conjugation with an Hfr cell sometimes? | An F- cell may acquire new versions of chromosomal genes. However, it remains an F- cell bc it did no receive a complete F factor during conjugation. |
| What is transduction by a Bacteriophage? | This is the transfer of bacterial genes by viruses |
| What is generalized transduction? | It occurs during lytic cycle of viruses in Bacteriophage |
| What are random fragments? | They are DNA from partially degraded host chromosome that are packaged by mistake in Bacteriophage, this makes a transducing particle |
| What is a transducing particle? | When DNA from host is packaged by mistake into a phage in Bacteriophage |
| Summarize transduction by a Bacteriophage? | When Bacterial genes are incorporated into viral genetic material due to mistakes that are made during the events within the cell. The phage will go on and infect another host and the infection will introduce the original DNA into the new cell |
| What is mobile genetic elements (MGEs)? | Discrete segments of DNA that move as units from one location to another within other DNA molecules |
| What are insertion sequences? | *Short pieces of mobile DNA *Short inverted repeats at the ends *Encode transposase enzyme |
| What are Transposons? | *Larger mobile DNA *encodes transpoase and can carry many genes (Antibiotic resistance) *Widely used tool in microbial genetics |
| How can mutation be beneficial? | |
| What causes mutations? | |
| How do mutagens affect the mutation rate? | |
| Compare conjugation between the following pairs: F+ x F-, Hfr x F- | |
| What types of genes do plasmids carry? |
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kzxiong
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