BIO207H5 Lecture Notes - Lecture 8: Reginald Punnett, Synteny, Genetic Linkage
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May or may not be better to read chapter 5 to understand this topic
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Tutorial 5 is based on this lecture, but not test 2.
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Recap from last lecture
alleles assort independently
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final allele distribution is random
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No crossing (obviously, due to different chromosomes)
Parental chromosomes = 100% in the gamete pool
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So Parental gametes ≠100%
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Parental chromosome combination ≠100% for each gamete (non-parental gametes)
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Genes on different chromosomes
No Genetic Linkage
Syntenic genes : Genes on the same chromosome
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Crossing over (frequency) αto distance
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Crossing over occurs between homologs
Alleles do NOT assort independently
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Final allele distribution is NOT random
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Parental >> recombinant chromosomes because crossing over does not happen
too often
Recombinants α to crossing over
Parental chromosomes have not been altered (no crossing over)
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Parental chromosomes ≠100%
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Recombination frequency, expressed as r, is calculated as R = number of recombinants /
total number of progeny
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When syntenic genes 'fairly' close to one another in distance (will be explained in later lecture)
Incomplete Genetic Linkage
Syntenic genes
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Crossing over αto distance -> cannot occur
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Alleles cannot assort independently
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Final allele distribution is NOT random
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Parental chromosomes = 100%
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because of non-parental gametes
Whenever we have >1 chromosome pairs (homolog pairs)
Parental chromosome combination ≠100%
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Parental gametes = 100%
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When syntenic genes are 'very' close
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Complete Genetic Linkage
Syntenic genes
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Crossing over occurs very frequently
When syntenic genes are 'very' far
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No Genetic Linkage
Lecture 8
Monday, August 8, 2016
4:00 PM
Lecture Page 1