What is a test cross and what genotype is used?

Question

What is a test cross and what genotype is used?

Answer 1

Test cross = the cross of an organism with an unknown dominant genotype with an organism that is homozygous recessive for that trait .  

Crossing with a recessive organism reveals any "hidden" recessive alleles a dominant individual has that prevents them from  breeding "true".  If off-spring are  recessive in phenotype then the tested individual has recessive alleles and is heterozygous for that trait.  Not desirable in breeding true to phenotype.

Answer 2

Vida a testcross is a cross between a known phenotypically dominant individual with a homozygous recessive type. This is a test to determine homozygosity or heterozygosity of the subject. After the cross the phenotypes of the individual are noted. If all the offspring manifest the dominant trait then the parent were homozygous. On the other hand if there are progenies which manifested the recessive trait then the parent is considered heterozygous. Say for example color of the pod of a pea plant. The dominant is green denoted as G and the recessive counterpart is yellow represented as g. A testcross can be any of these crosses.

GG x gg

Gg x gg

Hope this helps...