Module 6 Lesson 8 - 5
Completion requirements
Lesson 8 — Crossing Over Frequencies and Gene Mapping
Lesson Summary
By analyzing linked-gene crosses for recombinant phenotypes and by calculating recombinant frequencies, you can construct accurate gene maps for traits. This allows for a much clearer understanding of how or why certain traits tend to move together while others may not, even if they are on the same chromosome. The linkage of genes on chromosomes tends to reduce variability in offspring. Certain genes and their expression tend to move together. However, crossing over of chromosomes in meiosis acts as a counter to this trend. Crossing over increases variability in offspring by creating chromosome combinations not seen in parents.
During this lesson, you were to consider two focusing questions:
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How does crossing over in chromosomes relate to finding the locations of genes on chromosomes?
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What is the importance of knowing where genes are located on a chromosome?
Genes on the same chromosome tend to be inherited together. If they are not, it is a result of a cross over event during meiosis. The farther apart the genes are on a chromosome, the more likely a cross-over event is and the higher the recombinant frequencies are in the offspring.
By understanding where genes are located on chromosomes, geneticists can predict better the inheritance of those genes. Scientists can also design tests that detect the presence of those genes or genes known to be nearby.