Chapter 2 Summary

The topics covered in this chapter can be summarized as follows:

  • The alleles of loci in different chromosomes are inherited independently of each other.
  • The expected phenotypic ratio of a dihybrid cross is 9:3:3:1.
  • The 9:3:3:1 ratio can be modified if the loci are not simple dominant/recessive to each other,  if there are gene interactions, or if the two loci are linked.
  • A test cross gives a ratio of 1:1:1:1 for loci that assort independently.

Take a look at this video, Mendelian Genetics and Punnett Squares, from Professor Dave Explains (2017), which gives a great summary of what we have covered so far!


Professor Dave Explains. (2017). Mendelian genetics and Punnett squares [Video file]. YouTube.


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Introduction to Genetics Copyright © 2023 by Natasha Ramroop Singh, Thompson Rivers University is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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