Modelling the Inheritance of Linked and Unlinked Genes

To model the difference between linked and unlinked genes I used an activity I created that you should view here.

How it works:

By keeping some “alleles” linked and some “unlinked” we observe a difference in the inheritance pattern.

My initial instructions for this worksheet weren’t very clear but I think they are much better now. Ideally it will be printed so that the maternal genes are printed in one colour (let’s say pink, even though it’s a socially constructed convention. Let’s talk about that another time) and the paternal genes are a different colour. If I were to teach this again I would create a class set of laminated linked genes and laminated unlinked genes. The students spent far too long cutting them out themselves and I don’t think the actual process of cutting them adds anything to the learning experience.

Why is linkage important? The linkage of genes has huge implications for the inheritance of alleles. Genes which are on the same chromosome do not randomly segregated in meiosis. They physically cannot because they are on the same chromosome and so are inherited together.

Oh if only biology were so simple. NOT. That would be boooooooring! Evolution is way more sophisticated than that.

In fact, we have a process called crossing over that swaps a little bit of DNA between homologous chromosomes so your maternal and paternal DNA can be rearranged into each of your gametes. So if you can imagine, genes which are closer together are more likely to stay together. It would be very unlikely for a crossing over event to happen right at the exact spot where one gene ends and the other starts and so genes which are closer together tend to stay together.

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