Which histone protein is not part of the nucleosome structure?

H1

Explanation:

Histones H2A, H2B, H3 and H4 are known as the core histones which means that there are building nuclesome. H1 is known as the linker histone which binds to the "linker DNA" region between nucleosomes, helping stabilize the chromatin fiber.  The linker histone H1 binds the nucleosome at the entry and exit sites of the DNA, thus locking the DNA into place and allowing the formation of higher order structure.

b

explanation:

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.