Basically suffer genetic effect:
Palpebral (Eyelids) common weighs eyelid, the heredity of the person's sheet, double-fold eyelid is the gene pilot on the euchromosome in sufferring nucleolus, double-fold eyelid by dominance gene (usable A expresses) control, single-edged eyelid by recessive gene (usable A expresses) control;
The generation of odd, double-fold eyelid follows a person on in eyelid one carries eyelid flesh to have immediate concern. Carry eyelid flesh to have apparent thread when this outspread when to hypodermic, muscle systole causes adherent place cutaneous to shrink back, because the skin knits the integrated effect of a round flat piece of jade with a hole in its center, form double eyelid (double-fold eyelid) . And the cause of formation of single-edged eyelid lacks this kind of motive namely carry eyelid flesh fiber. The dominance gene A that afore-mentioned alleged control double-fold eyelid form, carry eyelid flesh fiber to form with this kind namely actually relevant. Generally speaking, a person that has dominance gene A (genotype is AA or Aa) expression should be double-fold eyelid, and expression of the person that genotype is Aa is single-edged eyelid.
Also have acquired effect:
However, individual development of the mankind is a very complex process, it should get the got-up action of other gene in genetic background, get even all sorts of inside, the influence of element of outer shroud condition, even if the person that genotype is AA or Aa, because carry,go up possibly also of development of eyelid flesh fiber not complete and expression does not give double eyelid. Should behave the person of double-fold eyelid originally from genetic composition, because the likelihood promotes growth of eyelid flesh fiber very not complete and present single-edged eyelid; Because carry,go up possibly also development of eyelid flesh fiber is very not complete and bring about palpebral dualism not apparent, or because of 2 eyes carrying development of eyelid flesh fiber to degree differs and form a small hole is the phenomenon that another single-edged eyelid, eye is double-fold eyelid; Appear possibly even such circumstance: ? Fetters does fan tear pattern of mu of さ of Xie of パ of chasm of pen of of carve Peng is narrow like You of Zhun of tiny stream lid to build vertebra to be ァ of male of of Dong of chimney of of Zai Chu of Xie ば is ⑺ box simian awl of family name paper Guo Yunyou a huge legendary turtle?
