Both words are used throughout the series, with slightly different meanings. Here's what I propose for our official usage.
変異体 へんいたい Henitai
Meanings: mutant, variant, genetic variant, mutated form
Tai means body and generally refers to the humanoid form.
変異株 へんいかぶ Henikabu
Meanings: mutant strain, variant strain
Kabu means strain (bacteria, virus, etc.).
http://www.virology.net/ATVGlossary.html
MUTATION
A rearrangement of genes or change in base pairs so they produce different effects within their environment.
VARIANT
A variation of a particular strain of virus or infective agent; slightly different in form or function.
BIOHAZARD 1
始祖ウィルス変異体を投与(Nov.10.1967)
Administered Progenitor virus mutants (Nov.10.1967)
2)変異体を含むB.O.W.の胚を、一種につき2個ずつ回収せよ。
Retrieve two embryos for each species of B.O.W. including the mutants.
This is interesting since its referring to mutated forms, in other words, irregular mutants/secondary exposed creatures like Plant 42.
No.1 History of Biohazard
[1967年]
▼11月
・建築家のジョージ・トレヴァーの妻ジェシカと娘のリサに「始祖ウィルス変異体」が投与される。
'Progenitor virus mutants' are administered to architect George Trevor's wife Jessica and daughter Lisa.
'Mutated forms of the Progenitor virus' works too.
Biohazard Outbreak
［調査依頼書］
報告にあったものとは違う種のようで、ウイルスによる変異体だと思われるが、こちらでは詳しく調べられない。
G変異体/G-IMAGO
Imago refers to the development cycle of an insect so 'G-Mutant' is more appropriate.
CODE: Veronica Alexander's Diary
やがて研究成果が出はじめ、始祖ウィルスの変異体を総じてT-ウィルスと呼ぶようになった。
Soon the research results began to rise and a variant of the Progenitor virus often came to be referred to as T-virus.
Wesker's Report II:
Female Specimen
「始祖ウィルス」から「生体生物兵器」を製造するために、その特性を強化した「ウィルスの変異株」を開発する。
To develop a 'variant strain' with enhanced properties in order to produce a 'Bio Organic Weapon' from the 'Progenitor virus'.
Nemesis
「ゾンビ」や「ハンター」を製造する為の「t-ウィルス変異株」はほとんどの「人間」に適応したのだが、脳組織を衰退させる問題があった。
バーキンはその問題を克服するべく、完全適応すれば脳への影響を最低限に抑える新しい「変異株」の抽出を行なった。
だが「その変異株」に対しては「適応する遺伝子を持った人間」が極めて少なかった。
遺伝子解析班のシミュレートでは、「1000万人に1人の人間」しか「タイラント」として発症せず、他はただ「ゾンビ」となるだけだったのだ。
研究が進めばもっと多くの「人間」が「タイラント」として発症する別のタイプの「t-ウィルス」も開発できるはずだった。
しかし、その研究をする為にも先ず「新しい変異株」に完全適応する「人間」が必要とされた。
The 't-virus variant strain' used to produce the 'Zombie' and 'Hunter' adapted to most 'men', but there was the problem caused by a decay of brain tissue.
In order to overcome this problem, Birkin extracted a new 'variant strain' which would minimize the effects on the brain if fully adaptive.
But an extremely small number of 'men with adaptable genes' existed for 'this variant strain'.
In a simulation conducted by the genetic analysis group, only 'one person in every 10 million people' displayed the initial onset of 'Tyrant', while the others simply became 'zombies'.
Further along in our research, we should be able to develop several types of 't-virus' which trigger the onset of 'Tyrant' in more 'men'.
But first we required a fully adaptive 'man' for this 'new variant strain'... [Enter Sergi 1991]
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I'd like to hear what our resident doctors have to say.
Basically, a mutant is something whose genetic code is different in some way from the source material, although I haven't seen the term applied to any transgenic modifications more sophisticated than a few nucleotides.
Viruses mutate all the time, and it could probably be said, for instance, that the strain of T-Virus which creates Crimson Heads is a mutant of an earlier strain. In contrast, Birkin tinkered extensively with the T-Virus in order to create a variant which could produce Tyrants; "mutant" would not be the most appropriate term for that virus. In either case, the term "strain" would be appropriate, and we should probably use that term to avoid confusion.
Technically, what we call "irregular mutants" would not best be described as mutants, although they possess mutations; while they are genetically different from their parent organisms due to the effects of the T-Virus, this difference is probably wildly variable from cell to cell due to the random nature of viral integration. As you can imagine, the scientific nomenclature isn't really equipped to describe this particular scenario.
However, since a precedent exists, we may as well continue to refer to such creatures as mutants.
"The last century showed us the evil face of physics. This century will show us the evil face of biology. This will be humanity's last century, Constance."
- A.X.L. Pendergast
Thanks. Regarless of precedent, what do you propose?
"For instance, let’s assume that you developed the ultimate bio-weapon. Well, what would you do? Fate is now in your hands." -Albert Wesker
Disregarding precedents, I would refer to all variations of the T-Virus as "strains" - for example, the Marcus prototype strain, the V-ACT strain, or the Raccoon City strain. Any B.O.W.s created through genetic manipulation of a human ovum would be "transgenic organisms." Any monsters created directly through infection of an adult or developing organism (i.e., not a single cell) would be "transduced organisms," including Tyrants, G-Types, and some "accidental" monsters. Any organism which is likely to be a result of genetic changes (induced by viral infection or otherwise) passed from parent to offspring could conceivably called a mutant. This might include the Grave Digger, Sliding Worms, and possibly Licker Betas (all of which are known to be reproductively viable), and potentially a variety of other arthropod monsters like the Brain Suckers and Drain Deimos.
Again, the current scientific vocabulary is ill-equipped to deal with the creatures of Resident Evil. While "mutant" may not be technically accurate as a descriptor for most monsters, it has entered the vernacular in much the same way as the word "theory," and I wouldn't begrudge people its use.
"The last century showed us the evil face of physics. This century will show us the evil face of biology. This will be humanity's last century, Constance."
- A.X.L. Pendergast
Newsbot, we should adopt this.
"For instance, let’s assume that you developed the ultimate bio-weapon. Well, what would you do? Fate is now in your hands." -Albert Wesker
Already have. General consensus is that variant = developed while mutant = natural.