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26 Cards in this Set
- Front
- Back
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what is syntenic?
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genes on the same chromo that are physically linked
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linkage group?
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genes inherited together
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linkage maps
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relative distances of markers on chromosmes
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who discovered genetic linkage?
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Thomas Morgan
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Explain Morgan's experiment
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white eyes (w)
minture wings (m) parents wm/wm add w+m+/y f1 all females while type and males white eyes, mini wings f2 mostly parental phenotypes, some about 36% were recombinent resutls: alleles assort together if close to chromo, closer on chromo more likely to remain |
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what two experiments proved it
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Creighton and McClintook
and stern |
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explain Crieghton and McClintook
and stern |
Crieghton and McClinktook
2 visual markers knob and part of chrom 9 which correlated with recombinant phenotypes same with stern |
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Crossing over occurs
what is a chiasma? Reciprocal exchange of Dna? |
prophase I of meiosis I
chiasma is site of crossing over Yes |
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What is the Holiday molecular mechanism of crossing over?
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explains how it happens
break and anneal to opposite chrom forming holliday intermediate chromo ends pull apart, making 4 arm intermediate cut by endonucleases in one of two planes |
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Holiday model predicts?
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50% chance that two gene loci at ends of chromo will physically exchange
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how to make genetic map
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key thing here is that number of genetic recombinants produced correlates with linkage relationship
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do a test cross with
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homo recessive or dominant...for genes involved (other parent is heter)
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results of cross test?
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if not linked all ratio of parental and recombinant will be 1:1
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what arrangement is cis and trans?
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w+M+/wm cis
w+m/M+w trans |
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1% cross over rate is
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1 map unit
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cross-over is more likely between
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distant genes
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measurement of crossing over is more accurate
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when gens are close together
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number of phenotypes for 3 point test cross
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eight
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can recombination rate reach over 50%
if so at 50% so what? |
no
1) on separate chrom or vary far apart |
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what are mapping functions for?
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after 7mu, the line starts to curve
recombination freq, underestimate so |
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difference between recombin and crossing over frequence
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recombin. frequency::: of markers
crossing:: acutal event double crossing oer |
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how to calculate recombination frequ?
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number of recombinatins/total
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they thought crossing over would occur when?
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prophase 1 at 4-chroma stage
or interphase prior to meiosis 2-chroma |
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what experiment proved it was on 4-chromatid?
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with orange bread mold
arrangement of ascospore (four gametes) in ascus indicate crossing overpattern, so can see gametes (all four types) results:: recombination and nonrecomm with 4-chroma if two-chroma no ration of recombin and nonrecombination |
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gene conversation is
and does what occurs with |
nonrececiprocal exchange of DNA
there is a switch between dna strands, "mismatch" results and invaded DNA is used as template similar genes from duplicated genes |
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mitoic recombination
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meisos can occur in somatic cells
seems to occur with heterozgous always adjacent |
