What are some techniques for genotyping?

[terryds]

I just wonder how to..
In textbook, it says using testcross (crossing the unknown genotype to the homozygous recessive genotype)
Again, how to know if it's homozygous recessive?
What device is used ?

 

[Ygggdrasil]

If you know that a trait is recessive, then individuals showing the recessive phenotype must be homozygotic. Plus, one can create lineages that are homozygotic at most loci by inbreeding a particular strain.

There are also a variety of molecular biology techniques to genotype individuals:
https://en.m.wikipedia.org/wiki/Genotyping