A test-cross is used to determine the genotype of a phenotypically dominant individual. To do this you mate the unknown individual with a individual and examine the phenotype of its offspring.

Explanation:

1. Test cross is done To identify whether an organism exhibiting a dominant trait is either homozygous or heterozygous for a specific allele, a scientist can perform a test cross.  

2. The organism which we want to check is crossed with an organism that is homozygous for the recessive trait, and the offspring of the test cross are examined.

3. Performed with an unknown dominant phenotype and homozygous  recessive.

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.