Question

(9 points) You are interested in studying recombination frequencies in wasps. You identify a queen that is heterozygous at three different loci on chromosome 5: G, H, and R. As queen wasps can produce haploid male offspring without fertilizing their eggs, you decide to look only at the genotypes of her male offspring in your analysis. Below is a list of the genotypes of her male offspring, and the number of individuals that fall into each genotypic class. 92 168 180 235 75 GhR GHR Ghr GHI 5 ghR ghr gHr GHR 242 A. The first step in your analysis is to identify the linkage phase of the alleles in the queen (the configuration of the alleles at each locus on her chromosomes). Based on the data above, what is the linkage phase of the alleles in the queen? Briefly explain how you came to this conclusion. (1 point) B. Which of the three loci is in the middle? How do you know? (1 point) C. What are the two closest genes and the genetic distance between them? Show your work. (1.5 points) D. Calculate the map distance to the first decimal place) between the gene in the middle and each of the other genes, and use this information to draw a genetic map showing the genes in order with the genetic distances indicated in the space below. Show your work. (2 points) E. When you compare the genetic map that you constructed to the newly sequenced wasp genome, you notice that the physical distance in base-pairs) between G, H, and R is different from what you would expect based on the genetic distance. Does this mean that your genetic map is incorrect? Briefly explain what could have caused this result. (1 point)

Answer 1

ANSWERS: A The best way to solve these problems is to develop a eystematic approach. Firest determine which of the genetypes are the parental genotypes. The genotypes found most frequently are the parental genetypes and a From the data provided, I it is clear that (Ghre) and (gHR) are parental genotypes. Also, the double crossover gametes are always in lewest freequency. Hence, feem the data we can infer that Ghoo and (He) are double crossovers Also, the double creessovere event noves the middle allele from one sister chrometid to the other. This effectively places the non- parental allele of the middle gene onto a chromosome with the parental alleles of two flanking genes. Hence, in the parental chreemosomes the R-gene must be in the middle , since the 'R allele in double ressover is now on the same chromosome as the G & h alleles, and the di allele at deuble crossover is on the same chremesome as g and it alleles of the parental type.

Hence, queen the linkage can be shown phase as of the alleles en follows: GR h. G reh double CROSOVUe. gret SRH (Greh/gRH). 6. The locus for the R-gene es in the middle which has been described previously in (@). The genes which are clsest will have lowest frequency of cressover between them. Hence, the genotypes GHR and ghre preoduced by single crossover between G-and-'R' bei are in the lowest frequency among single crossover Greh GRH single crossover between G and G RH R becus. So, the distance between G and R genes es - No. of recombinanti (Steam single & double crossover) x 100 Total no. of gametes x 100 = 35.6 cm 1900 180 + 168 + 3+5

Greh crossover R and 4 D) Now, the crossover between the R and H decus can be shown as follows: ски single between GRH. beus. Hence, the distance between R and H genes es : = No. of reecombinants (fream single & double crossover) Total no. of fametes = 235+ 242 + 3 +5 x 1a - 48.5 cm X10 Hence, the genetic map can be shown as below; + + 35.6 CM 48.5CM — + A + too I 84. 1 CM E) If the physical distance between G, H and R is different from our expectation based on genetic distance, this doesn't mean that one genetic map is completely incorrect. It's just an approximation based on the assumption that creessing over acceves reandomly. Hence, the distance between leci represents recombination frequency & esn't equivalent to precise physical distance.

As per Chegg guidelines, I'm permissible to answer only the first four sub-parts of a question. However, I've answered the first five sub-parts with detailed explanation. Thanks.