Chapter 17. Chapter 17: Mapping Chromosomal Translocations

Introduction

Unpacking the Problem
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You must read each slide, and complete any questions on the slide, in sequence.

In corn, the allele Pr stands for green stems, pr for purple stems. A corn plant of genotype pr/pr that has standard chromosomes is crossed with a Pr/Pr plant that is homozygous for a reciprocal translocation between chromosomes 2 and 5. The F1 are semisterile and phenotypically Pr. A backcross with the parent with standard chromosomes gives 764 semisterile Pr, 145 semisterile pr, 186 normal Pr, and 727 normal pr. What is the map distance between the Pr locus and the translocation point?

Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.

  • Part A (steps 1-3): Define the terms used in the problem.
  • Part B (steps 4-6): Set up the mapping problem.
  • Part C (step 7): Solve the mapping problem.

Question

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
1

In corn, the allele Pr stands for green stems, pr for purple stems. A corn plant of genotype pr/pr that has standard chromosomes is crossed with a Pr/Pr plant that is homozygous for a reciprocal translocation between chromosomes 2 and 5. The F1 are semisterile and phenotypically Pr. A backcross with the parent with standard chromosomes gives 764 semisterile Pr, 145 semisterile pr, 186 normal Pr, and 727 normal pr. What is the map distance between the Pr locus and the translocation point?

Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.

  • Part A (steps 1-3): Define the terms used in the problem.
  • Part B (steps 4-6): Set up the mapping problem.
  • Part C (step 7): Solve the mapping problem.

Question

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1

In corn, the allele Pr stands for green stems, pr for purple stems. A corn plant of genotype pr/pr that has standard chromosomes is crossed with a Pr/Pr plant that is homozygous for a reciprocal translocation between chromosomes 2 and 5. The F1 are semisterile and phenotypically Pr. A backcross with the parent with standard chromosomes gives 764 semisterile Pr, 145 semisterile pr, 186 normal Pr, and 727 normal pr. What is the map distance between the Pr locus and the translocation point?

Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.

  • Part A (steps 1-3): Define the terms used in the problem.
  • Part B (steps 4-6): Set up the mapping problem.
  • Part C (step 7): Solve the mapping problem.

Question

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
1

In corn, the allele Pr stands for green stems, pr for purple stems. A corn plant of genotype pr/pr that has standard chromosomes is crossed with a Pr/Pr plant that is homozygous for a reciprocal translocation between chromosomes 2 and 5. The F1 are semisterile and phenotypically Pr. A backcross with the parent with standard chromosomes gives 764 semisterile Pr, 145 semisterile pr, 186 normal Pr, and 727 normal pr. What is the map distance between the Pr locus and the translocation point?

Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.

  • Part A (steps 1-3): Define the terms used in the problem.
  • Part B (steps 4-6): Set up the mapping problem.
  • Part C (step 7): Solve the mapping problem.

Question

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iRU0JnTPH/4cL5Pq8Obv8+zslKZ8NJ1Mi8WOQZRgO4gQQ85kxC4hx4Lu+fxm54fdrbpkhV8Q3aRsLXCiB0sA97k4zUF0ACp1zD2XPdk8Bia7O9PkEk00RbWXTnK5Kn070UDwEeJiFX5o7YoBRdHkRqJOTpTlvZs8qfDO8ql/VghHyRK3Rrt3T4T+l1hx8y/g4lnvZ9BnfbQk0v0+ya5zArOzWhvvFecAWz62gjexh1JoytCp9Zz+3CJQxT6cDyX1S/At5uK6QJgNo7ZZ98wTHw0qYcNogJGksDobUKNG3BGXMPjuwHEHKdbpFMShHpNqoZFr1IjU3NWd16nKda4Z6GwCd70n0W6v+tcwRoHpyYOU7XD6g+h3XyTiO64o8/1/71ZmXvwWjtMNkh7v2r0C+j7VRyClmWnXvV1vlqZqUdwpEC+7VOIZFAS+xm2l3USCbtnw4gnsm65JY/l/T5ecPBX8JA0TvisBUk6YHM9X7v01stQgcc0=
1

In corn, the allele Pr stands for green stems, pr for purple stems. A corn plant of genotype pr/pr that has standard chromosomes is crossed with a Pr/Pr plant that is homozygous for a reciprocal translocation between chromosomes 2 and 5. The F1 are semisterile and phenotypically Pr. A backcross with the parent with standard chromosomes gives 764 semisterile Pr, 145 semisterile pr, 186 normal Pr, and 727 normal pr. What is the map distance between the Pr locus and the translocation point?

Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.

  • Part A (steps 1-3): Define the terms used in the problem.
  • Part B (steps 4-6): Set up the mapping problem.
  • Part C (step 7): Solve the mapping problem.

Question

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1

In corn, the allele Pr stands for green stems, pr for purple stems. A corn plant of genotype pr/pr that has standard chromosomes is crossed with a Pr/Pr plant that is homozygous for a reciprocal translocation between chromosomes 2 and 5. The F1 are semisterile and phenotypically Pr. A backcross with the parent with standard chromosomes gives 764 semisterile Pr, 145 semisterile pr, 186 normal Pr, and 727 normal pr. What is the map distance between the Pr locus and the translocation point?

Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.

  • Part A (steps 1-3): Define the terms used in the problem.
  • Part B (steps 4-6): Set up the mapping problem.
  • Part C (step 7): Solve the mapping problem.

Question

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1

In corn, the allele Pr stands for green stems, pr for purple stems. A corn plant of genotype pr/pr that has standard chromosomes is crossed with a Pr/Pr plant that is homozygous for a reciprocal translocation between chromosomes 2 and 5. The F1 are semisterile and phenotypically Pr. A backcross with the parent with standard chromosomes gives 764 semisterile Pr, 145 semisterile pr, 186 normal Pr, and 727 normal pr. What is the map distance between the Pr locus and the translocation point?

Unpack the Problem: Break this problem into several parts and arrive at a solution using this guided, step-by-step approach.

  • Part A (steps 1-3): Define the terms used in the problem.
  • Part B (steps 4-6): Set up the mapping problem.
  • Part C (step 7): Solve the mapping problem.

Question

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1

Conclusion

This is essentially a dihybrid mapping problem in which one of the gene loci has been replaced with the translocation break point. Recognizing this and that both green stems and semisterility are dominant in the heterozygote makes it possible to choose the proper tester to perform the backcross. The tester in this case is the parent that is purple stemmed and has normal chromosomes (since these are recessive in the F1). The progeny from the backcross are not in a 1:1:1:1 ratio and instead are grouped into a large number of parental type offspring and a much smaller group of recombinants. The latter group results from crossovers between the Pr locus and the translocation breakpoint on either chromosome 2 or 5 (you cannot tell which from the data provided). The number of recombinants is the sum of the two smaller classes. The frequency of recombinants is that number divided by the total progeny. In other words, (145 + 186)/(145 + 186 + 727 + 764) = 331/1822 = 0.1817. As a percentage, this is 18.17% or 18.17 map units.