How did life evolve? There are different factors that can determine whether a female or male creature develops.
Амьдрал яаж эхэлсэн бэ? Аливаа бодгаль эр, эсхүл эм хүйстэй болж хөгжихөд олон хүчин зүйл нөлөөлдөг.
In some species, sex is determined by the temperature in which their eggs grow. In other species, the amount of food can affect how many females or males are born.
Зарим төрөл зүйлийн хувьд өндөг бойжих хэмээс хамаардаг бол идэж буй хүнсний хэмжээнээс хамааран эр, эсхүл эм амьтан өсч өндийх нь бий.
However, in mammals it is the sex chromosomes, and specific genes on these sex chromosomes, that control whether an embryo develops as a female or a male.
Хөхтөн амьтны хувьд хүйс тодорхойлогч хромосом, тусгай ген эмбрио чухам ямар хүйстэй болохыг тодорхойлдог юм.
Generally in mammals, females have two X chromosomes (XX), while males have an X and a Y chromosome (XY).This may seem like a simple rule of nature, but actually it’s not. In fact, there are many different ways a species can determine sex through their chromosomes, a good example being birds, which have very different sex chromosomes from mammals called ZW chromosomes.
Ерөнхийдөө, хөхтөн амьтдын хувьд эм нь хоёр ИКС , эр нь ИКС, ИГРИК хромосомтой байдаг. Хэдийгээр энэ нь байгалийн тогтсон хууль боловч бодгалийн хүйс төрөл зүйл бүрт өөр өөр хромосомоор тодорхойлогддог. Үүний тод жишээ хөхтөн амьтнаас өөр ЗЭТ ДАБЛЬЮ хромосом бүхий шувуу юм.
What’s interesting about the chromosomes of the mammalian platypus (Ornithorhynchus anatinus) is that they appear to bend many of the traditional rules about what normal mammalian chromosomes should be. First, the ptatypus is the only mammal which has mircochromosomes. Microchromosomes are very small chromosomes, which look like dots, that have been found in birds but not in other mammals. Second, although the platypus uses XY sex chromosomes like humans, they have five times the number of X and Y chromosomes.
Platypus females have 10 X chromosomes and platypus males have five of each X and Y chromosomes. The high number of sex chromosomes in the platypus is the reason scientists like to study them, so that they can understand more about how mammals sex chromosomes are sorted and inherited.
To further complicate the story, the platypus appears to be lacking the essential gene that is found in all other mammals and is required to make males. In other mammals, this specific gene is found on the Y chromosome. However, in platypus males this gene cannot be found on any of its five Y chromosomes. To dare, it still remains a mystery how a platypus develops a a male without the presence of this sex-determining gene. The search is now on to find exactly what does control male development in the platypus.
It seems strange platyps chromosomes have alot to offer. Through stuying the platypus, we will unlock more secrets about how the evolution of sex determination occured in mammals.
Courtesy of Megan Wright, PhD student from Discipline of Genetics in the School of Molecular and Biomedical Science, University of Adelaide.