Table of contents
- 1. Introduction to Genetics51m
- 2. Mendel's Laws of Inheritance3h 37m
- 3. Extensions to Mendelian Inheritance2h 41m
- 4. Genetic Mapping and Linkage2h 28m
- 5. Genetics of Bacteria and Viruses1h 21m
- 6. Chromosomal Variation1h 48m
- 7. DNA and Chromosome Structure56m
- 8. DNA Replication1h 10m
- 9. Mitosis and Meiosis1h 34m
- 10. Transcription1h 0m
- 11. Translation58m
- 12. Gene Regulation in Prokaryotes1h 19m
- 13. Gene Regulation in Eukaryotes44m
- 14. Genetic Control of Development44m
- 15. Genomes and Genomics1h 50m
- 16. Transposable Elements47m
- 17. Mutation, Repair, and Recombination1h 6m
- 18. Molecular Genetic Tools19m
- 19. Cancer Genetics29m
- 20. Quantitative Genetics1h 26m
- 21. Population Genetics50m
- 22. Evolutionary Genetics29m
4. Genetic Mapping and Linkage
Mapping Genes
2:41 minutes
Problem 17b
Textbook Question
Textbook QuestionDrosophila females homozygous for the third chromosomal genes pink and ebony (the same genes from Problem 16) were crossed with males homozygous for the second chromosomal gene dumpy. Because these genes are recessive, all offspring were wild type (normal). F₁ females were testcrossed to triply recessive males. If we assume that the two linked genes, pink and ebony, are 20 mu apart, predict the results of this cross. If the reciprocal cross were made (F₁ males—where no crossing over occurs—with triply recessive females), how would the results vary, if at all?
Verified Solution
This video solution was recommended by our tutors as helpful for the problem above
Video duration:
2mPlay a video:
Was this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Linkage and Genetic Mapping
Linkage refers to the tendency of genes located close to each other on a chromosome to be inherited together. Genetic mapping uses recombination frequency, measured in map units (mu), to determine the distance between genes. A distance of 20 mu indicates a 20% chance of recombination occurring between the pink and ebony genes, which affects the phenotypic ratios of offspring in genetic crosses.
Recommended video:
Guided course
07:33
Chi Square and Linkage
Testcross
A testcross involves breeding an individual with a dominant phenotype but unknown genotype with a homozygous recessive individual. This method helps determine the genotype of the dominant individual based on the phenotypes of the offspring. In this scenario, the F₁ females are testcrossed to triply recessive males to reveal the inheritance patterns of the linked genes.
Reciprocal Cross
A reciprocal cross is a breeding experiment where the sexes of the parents are switched in two separate crosses. This allows researchers to determine if the inheritance pattern is influenced by the sex of the parent. In this case, crossing F₁ males with triply recessive females would yield different results due to the absence of crossing over in males, affecting the distribution of phenotypes in the offspring.
Recommended video:
Guided course
26:08
Trihybrid Cross
Related Videos
Related Practice