Dihybrid Crosses and Genes Relinked

Updated presentation for 2011.

Link to more class resources here: 10.2 Dihybrid Crosses and Gene Linkage

If you want to download an editable version of the file, please make a donation to one of my charities at Biology4Good. Click here for more information.

About Stephen

International Educator: China via Japan, Indonesia & the UK. Director of Innovation in Learning & Teaching. Science educator. Twitterist (@sjtylr), dad and bloggerer. MA International Education & current EdD student. Experienced Director of Learning & MYP Coordinator. Interested in curriculum, pedagogy, purposeful EdTech and global competence. Find out more: http://sjtylr.net/about. Science site: http://i-biology.net.

Posted on May 12, 2011, in AHL, IBDP Biology and tagged , . Bookmark the permalink. 2 Comments.

  1. Mr. T,

    Could you please explain how one knows which allele goes on which chromosome in a linked gene?
    It seems that if the gene is XxLl, then the dominant genes will go together and the reccessive genes will go together on each chromosome, (XL and xl)?
    If the genotype is XXLl though, the dominant gene will have to link with one of the reccessive genes (XL Xl…)

    Is there a general rule?

    Mr. Link

    • Good question Mr Link!

      In the Biology subject guide, it states that they will use the standard notation for linked genes in questions, i.e. A B or a b. Another alternative notation is AB/ab, which denotes gene linkage, though this is not used in the subject guide.

      You should not have to make the assumption of which allele is on which chromosome. I will add a slide to clarify this. EDIT – added to slides 47-49 (changes take a while to appear on embeds).

      I hope this helps,


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