G214 SU2 Mapping

• Recombinant

  Offspring whose phenotype differs from the parental due to crossing over of genetic material
• What is the percentage of parental and phenotype frequencies in independent assortment?

  50% parental and 50% recombinant
• What is the percentage of parental and recombinant phenotype frequencies in linkage with no crossing over?

  100% parental phenotype
• what is the percentage of parental and recombinant phenotype frequencies in linkage with crossing over

  >50% parental phenotype and <50% recombinant phenotype
• what is recombination frequency

  the percentage of recombinant progeny; can be used as an indication of the physical distance separating any 2 genes on a chromosome
• what is interlocus distance

  number of crossover events between 2 loci is equal to the distance between them
• What are single crossovers (SCO)

  Crossing over between 2 linked genes - certain percentage (<50%) of F2 offspring as result of crossing over
• How do you calculate the probability of 2 crossing overs occuring simultaneously?

  Multiply product of their individual probabilities
• Which percentage is lower? Double crossovers or single crossovers


  double cross overs
• What type of crossing overs are the parentals?

  non crossing over
• does the parentals have the highest or lowest percentage and why?

  Highest - most common due to no crossing over
• Does DCO have the highest or lowest percentage?

  Lowest - due to a low probability
• What does chiasma interference affect?

  the number of DCOs
• how do you calculate the coefficient of coincidence?


  observed DCO / expected DCO
• What does it mean when C = 0,804?

  Only 80% DCO is observed from the expected DCO
• How do you calculate the interference (I)?

  I = 1 - C
• Is the DCO obs or DCO exp bigger in positive interference?

  DCO exp (C<1)
• Is the DCO obs or DCO exp bigger in negative interference?

  DCO obs (C>1)
• How many types of offspring will 2 linked genes have?


  4 total - 2 represent parental phenotype and 2 represent SCO
• How many types of offspring will 3 linked genes have?

  8 in total - 2 parental phenotype, 2 DCO and 4 represent 2 SCO
• List the steps in determining linkage of 3 genes

  1. Sort phenotypes by complimentary and frequency
  2. Calculate the total number of progeny
  3. Calculate the recombination frequencies and distances
  4. calculate order of genes by comparing theoretical to observed
  5. Apply the distances to the correct linked genes
• Why would 3 linked genes have only 6 total classes

  No DCO present
• Is the recombinant frequency additive?

  No