Term
| what is the RF of linked genes? why? |
|
Definition
<50%
because crossing over does not always occur and does not always occur between the same genes |
|
|
Term
| what is the site of crossing over called? |
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Definition
|
|
Term
| what is the RF for independant assortment? |
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Definition
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Term
| what is the proper notation for two genes whose linkage relationship is unknown? |
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Definition
A/a . B/b
(Both alleles of gene 1, dot, both alleles of gene 2) |
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Term
| what is the correct notation for 2 genes that are known to be unlinked? |
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Definition
A/a;B/b
(both alleles of gene 1, semicolon, both alleles of gene 2) |
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Term
| what does a slash mean in gene notation? |
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Definition
| genes on either side of slash are on homologous chromosomes |
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Term
| what is the notation for 2 genes that are known to be linked? |
|
Definition
Ab/aB(ex.)
(allelic combination on one homolog, slash, allelic combination of other homolog) |
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Term
| what is the RF for linked genes w/no crossing over? |
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Definition
|
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Term
| what is the name for the location of a gene on a chromosome? |
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Definition
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Term
| who realized that the RF of linked genes can be directly related to their distance from each other on the chromosome? |
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Definition
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|
Term
| what is another name for a map unit? |
|
Definition
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|
Term
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Definition
| the distance on a chromosome such that the RF by crossing over is 1% |
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Term
| in a 3 point testcross, how can the parental allelic combinations be determined? |
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Definition
| the 2 phenotypes that occur in the highest frequency in the offspring will be the parental types |
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Term
| the 8 types of offspring from a 3-point cross can be divided into 4 groups based on the frequency in which they occur in offspring. what do these groups represent? |
|
Definition
most frequent - parental combinations
2nd most frequent - singel cross-over between pair that is farther apart
3rd most freq.- single crossover between pair that is closer together
least freq.- double crossover |
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Term
| why do the distances between gene 1-2 and 2-3 not total the distance 2-3 in a 3-point cross? |
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Definition
| b/c double crossovers leave genes in the parental form half of the time, so half of these are counted as parentals and not as double crossovers |
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Term
| how is the distance between the outer genes in a 3-point cross calcualted accurately? |
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Definition
| add the distance of genes 1-2 and 2-3 or count the double crossover frequency twice when calculating RF |
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Term
| what is the easiest way to recognize the order of genes in a 3-point cross? |
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Definition
| compare largest frequency group to smalles freq. group. the gene that flip-flops is the middle gene |
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Term
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Definition
| when a crossover in one region decreases the likelihood of a crossover in a nearby region |
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Term
| how is interfernce calculated? |
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Definition
| I = (# double x-overs missing)/(# double x-overs expected) |
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Term
| how do you calculate the # of double x-overs that are expected from an experiment? |
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Definition
| multiple RF of gene 1-2 by RF of gene 2-3 to get expected RF of double x-over. multiply this by the total progeny to get expected count |
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|
Term
| how are gene distances larger than 50 mu determined? why is 50 the largest that can be detected directly? |
|
Definition
-internal distances added together
-50% is maximum RF from crossing over (and highly unlikely) |
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Term
| explain conjugation, transformation, and transduction. |
|
Definition
conjugation - genetic passing directly
transformation - uptake of DNA from environment
transduction - genetic passing via phage
(DON'T use the word 'exchange') |
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Term
| what two characteristics are common to the 3 methods by which prokaryotes pass DNA? |
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Definition
1. is a partial passing
2. is one-directional (not an exchange) |
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Term
| how are bacterial colony phenotypes differentiated? |
|
Definition
1. Biochemical requirements(prototrophy/auxotrophy)
2. Resistance
3. Colony morphology |
|
|
Term
| define prototrophy and auxotrophy |
|
Definition
prototrophy - no specific nutrient requirements, can grow on minimal media
auxotrophy - specific, complex nutrient requirements (amino acids, vitamins, etc) |
|
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Term
| how could you select for an auxotroph requiring a specific growth factor? |
|
Definition
1. grow in minimal media broth w/penicillin (kills growing cells so kills prototrophs)
2. plate on minimal media that contains the specific growth factor |
|
|
Term
| explain the characteristics of an F plasmid? |
|
Definition
1.replicates inside cell, passed on with cell division
2.causes pili
3.does not conjugate w/other F+
4.can cross in and out of the bact.csome
5.can cause entire bact.csome to be transferred via conjugation |
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|
Term
|
Definition
| a bacteria containing an F plasmid that has been integrated into the main csome and has crossed back out, taking some of the csome with it |
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Term
|
Definition
| when an F prime factor transfers a main csome gene to another cell |
|
|
Term
| what is an Hfr factor? what does it stand for? |
|
Definition
an F factor that is integrated into the main csome
High Frequency of Recombination |
|
|
Term
| what are the 2 ways that a bacterial genome can be recombined? |
|
Definition
1.sexduction via F prime
2.Hfr |
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|
Term
| what bacterial crosses result in no recombintion? high? low? |
|
Definition
none - (F+ x F+) OR (F- x F-)
High -(Hfr x F-)
Low - (F+ x F-) |
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|
Term
| why is there some recombination in an (F+ x F-) cross? |
|
Definition
| there will be rare instances of integration forming a few Hfr cells |
|
|
Term
| what types of strains are used for prokaryote genomic mapping? |
|
Definition
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|
Term
| if you crossed an Hfr x F-, how would you recover recombined bacteria? |
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Definition
| use an Hfr strain that is sensitive to some factor and an F- strain that is resistant. After conjugation, cells that are still resistant must be F- b/c transfer cannot occur the other direction. (would NOT be able to map resistance gene however) |
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|
Term
| what are the 2 methods discussed for mapping bacterial genomes? |
|
Definition
interrupted mating and
recombination-based mapping |
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|
Term
| how is conjugation stopped in interrupted-mating? |
|
Definition
|
|
Term
| what is the pro and con of interrupted mating? |
|
Definition
1. can give gene order over long distance
2.low resolution |
|
|
Term
| what are the pro and con of recombinant-based mapping? |
|
Definition
1.high resolution
2.only good over short distances |
|
|
Term
| what is map distance in controlled mating measure in? |
|
Definition
|
|
Term
| what do you need to know about your Hfr strain for recombinant based mapping? |
|
Definition
| need to know which gene enters last |
|
|
Term
| how do you know which gene is in the middle from recombinant-based mapping? |
|
Definition
| the combination that DOESN'T appear represents the one that would involve a triple crossover |
|
|
Term
| why do you select for the Hfr gene that enters last in recombinant-based mapping? |
|
Definition
| this insures that a crossover has occurred somewhere to the left and right of this gene |
|
|
Term
| what is especially interesting regarding bacterial transformation? |
|
Definition
|
|
Term
| what is used to increase transformation competance? why? |
|
Definition
heat or osmotic stress
-weakens the cell membrane/wall |
|
|
Term
| what is the co-transformation rate? |
|
Definition
| the rate at which 2 genes are transformed together |
|
|
Term
| what is the pro and con of using cotrasformation rate for gene mapping? |
|
Definition
1.high resolution at short distances
2.only works if genes are pretty close together |
|
|
Term
| what determines the rate of trasnformation? |
|
Definition
| the amount of DNA in the environment |
|
|
Term
| what are phages grown on? what is growth called? |
|
Definition
grown on a bacterial lawn
colonies called plaques |
|
|
Term
|
Definition
| the process by which a bacteriophage infects a bacteria and turns it into a virus factory which ends in cell lysis and phage dispersal |
|
|
Term
| how can phage genes be mapped? |
|
Definition
double infection
-infect host with 2 types of phages
(# recombinant phages)/(total # of phages) = RF |
|
|
Term
| how and where does phage dna recombine? |
|
Definition
| via crossing over in a host cell's cytoplasm |
|
|
Term
| what is the difference between a virulent phage and a temperate phage? |
|
Definition
virulent - performs lytic cycle only
temperate - does lysogenic cycle and lytic cycle |
|
|
Term
| what is the lysogenic cycle? |
|
Definition
| integration of phage dna into the host csome, rides along, comes out later and starts lytic cycle |
|
|
Term
| what type of virus is HIV? |
|
Definition
|
|
Term
|
Definition
| phage DNA which is inserted in a host csome (during lysogenic cycle) |
|
|
Term
| how is bacterial DNA transferred in transduction? |
|
Definition
| when phages form, some contain bacterial DNA instead, which is spread to recipient via phage |
|
|
Term
| what is generalized transduction? |
|
Definition
| when a random piece of DNA is transduced by chance |
|
|
Term
| what is specialized transduction? |
|
Definition
| only the DNA on the host csome near where the phage integrated is transduced |
|
|
Term
| what type of phages perform specialized transduction? |
|
Definition
|
|
Term
| how can tranduction be used to map genes? |
|
Definition
co-transduction frequency
-rate at which 2 genes are tranduced together (like co-transformation) |
|
|
Term
| what are the 4 ways to map bacterial genomes? |
|
Definition
1. recombinant-based
2. interrupted mating
3. Co-transformation
4. Co-transduction |
|
|
Term
| what is 'vertical' and 'horizontal' gene transfer? |
|
Definition
vertical - from parent to offspring (eukaryotes)
horizontal - from donar to 'neighbor', among 'peers'(prokaryotes) |
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