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Name: Heather M.
Status: Student
Age: 15
Location: N/A
Country: N/A
Date: N/A 

My teacher tells me that you can not write the little letter frist in the combinations. For example tT. But then I read you can in my Biology Book but he still says no. So can you write it tT or is it Tt?

Heather, you will find that it will be very confusing for you if you write the little letter first. The convention of the big letter first makes it easier to read and interpret results from the Punnett square, as well as determining the phenotype from any genotype. The only time that I've ever seen the little letter first as being acceptable is when one is trying to show exactly which allele came from which parent. For example, if you cross Tt and Tt, there are two ways you get offspring that are Tt: one where the mother donates the t, and one where the father donates the t. Writing the little letter first would suggest that the mother donated the t - it would be useful in some probability problems with genetics. Does that make sense?

Ellen Mayo

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