[Pet biology 101: Phenotype]

Introduction

Phenotype

As far as biology is concerned there are two groups of people, namely pet owners and pets. Pet owners have the phenotype PO, while pets have the phenotype PH (pethood). The male Y chromosome prevents the expression of the PH phenotype by male humans, so all known PH phenotypes are born female. Pet owners on the other hand can be of either sex.

Hormones

There are four hormones of importance to pet biology for now: estrogen, oxytocin, somatotropin and luteinizing hormone.

Estrogen is a category of female hormones from which two are relevant at this moment, namely estradiol (estrogen E2) and estroxin (estrogen E5). Estradiol is important here because once puberty is reached estradiol triggers the production of estroxin.
Estroxin is important because the estroxin level governs the expression of the pet subtypes (see Pet biology 102: Phenotype special cases for details)

Oxytocin is important because the interaction of oxytocin with the human organism determines if one is a pet owner or a pet.

Somatotropin, a growth hormone AKA GH or HGH (human growth hormone), is a hormone that stimulates cell reproduction and cell regeneration in humans and other animals.

Luteinizing hormone (LH) AKA lutropin is used as a remedy for Pethood Gonal Dormancy. All PH phenotypes are born with Pethood Gonal Dormancy or PHGD for short. PHGD keeps the ovaries dormant, which makes PH phenotypes naturally sterile. This can however be remediated by giving luteinizing hormone AKA lutropin which causes an LH surge and triggers ovulation.

Hormone receptors

Both estrogen and oxytocin have receptors in the human body. Foremost are the oxytocin receptors OXTR PO and OXTR PH. As the name implies pet owner phenotypes are born with OXTR PO receptors and pethood phenotype are born with OXTR PH receptors. Combined with the estroxin level, this yields the behavior attributed to the PO or PH phenotype. Oxytocin binding to the OXTR receptors before the start of the production of estroxin may cause subconscious preferences in interacting with other people. Oxytocin is nicknamed the cuddle hormone after all because it affects bonding.

Of the estrogen receptors, ER-delta is the most relevant at this moment because only PH-2 phenotypes are born with it. Estroxin binding to the ER-delta receptor triggers the somatotropin hormone and prepares the organism to accept Mobile Genetic Elements (MGE) from other species to prepare the body for the transformation typical to the PH-2 phenotype.

Mobile Genetic Element (MGE)

Ever since the first multi-cellular organism, species have been incorporating foreign genetic material to have an evolutionary edge, the amount of this foreign genetic material is nowadays known as the MGE count or Mobile Genetic Element count. For the average person approximately 50% of the genome is thought to be MGEs.

Puberty

Pet owner phenotype PO

Between the age of 12 and 18 years on average, all people proceed through puberty as their hormones (estradiol and testosterone taking the lead here) have their first boost resulting in the know physical changes marshaling the coming of age. At the end of puberty these hormones level off.

Pethood phenotype PH-1, AKA common pet

Instead of plateauing, a pet's estroxin level keeps increasing beyond the coming of age (18 years). This effectively causes a second puberty, this one focused on psychological changes.

While your average PO will have graduated high school by now and planning to attend college or find a job, developing an affinity for a career, as a pet one will develop an affinity to a certain kind of animal. Comparable to the former puberty, this pet-puberty can be a confusing time until one finds the animal that fits one's personality. Some will know it immediately, almost intuitively, they just know and feel which one is right for them, others may need more time figuring this one out.

Either way, the future is set by now. All a pet is expected to do is find a good owner. The prime directive here is that all relations between owner and pet are mutually voluntary.

Pethood phenotype PH-2, AKA transgenic pet

Like the PH-1 phenotype, a PH-2's estroxin level keeps increasing beyond the coming of age (18 years). A transgenic pet experiences similar psychological changes as a common pet, but also undergoes physical changes as somatotropin transforms the body to express the accepted MGEs of another species. Henceforth named the donor species. This means that the kind of pet one is is not only determined by an affinity to a kind of animal, but by the environment she grew up in. The chances you turn out to be a certain type of transgenic pet are in direct correlation to the proliferation of the kind of animal in your surroundings.

On average, the kind of transgenic pet you are should be set after having your pet-puberty that lasts about a year, in which times your transformation to expressing the basic characteristics of the donor species will take place.

Summary chart