1 / 8

Understanding Gene Linkage and Mapping in chromosomes

Genes can be mapped to specific locations on chromosomes using crossover frequencies and linkage maps. Learn how Mendel, Punnett, Bateson, and Sturtevant's work with pea plants and fruit flies contributed to our understanding of gene linkage. Explore how chromosomes exchange genes during meiosis and how crossover frequencies can estimate distances between genes.

blackburnk
Download Presentation

Understanding Gene Linkage and Mapping in chromosomes

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. KEY CONCEPT Genes can be mapped to specific locations on chromosomes.

  2. Background work by scientists: • Mendel: crossed pea plants and determined the 9:3:3:1 ratio in dihybrid crosses. • Concluded: 2 alleles/trait and alleles assort independently • Punnett and Bateson: crossed pea plants and found that the dihybrid ratios differed from 9:3:3:1 • Concluded: some traits must be linked

  3. Mutant Wild type Gene linkage was explained through fruit flies. • Morgan found that linked traits are on the same chromosome. • Conclusion: Chromosomes, not genes, assort independently during meiosis.

  4. Sturtevant’s hypothesis: • The frequency of cross-overs during meiosis is related to the distance between genes: the greater the distance, the greater the frequency of crossover • S. experiments: studied linked traits in fruit flies, used crossover frequencies to make linkage maps • Making a linkage map: • Crossover frequencies are converted to map units • Can find the relative location of genes

  5. Chromosomes exchange homologous genes during meiosis. • Linked genes are not inherited together every time.

  6. Linkage maps estimate distances between genes. • The closer together two genes are, the more likely they will be inherited together. • Cross-over frequencies are related to distances between genes. • Linkage maps show the relative locations of genes.

  7. Cross-over frequencies can be converted into map units. • gene A and gene B cross over 6.0 percent of the time • gene B and gene C cross over 12.5 percent of the time • gene A and gene C cross over 18.5 percent of the time

  8. IMPORTANT: 1% crossover = 1 map unit • By knowing all crossover frequencies, the relative location of the genes can be determined. • (This is NOT an actual map of the physical distance between genes.)

More Related