为什么有些人胡子和头发的颜色不一样?

2021年1月15日
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Why do some men have red beards, but not red hair?

为什么有些人胡子和头发的颜色不一样?

为什么有些人胡子和头发的颜色不一样?

It’s relatively rare to see a redhead — just 1% to 2% of humans are natural gingers. So, you might do a double-take if you see a man sporting a reddish or even a full-blown red beard, even though he is clearly not a carrot top.

红头发的人相对来说比较少见,只有1%到2%的人是天生的红头发。所以,即使你看到一个留着红胡子却不是红头发的人,你可能也会很好奇。那么,这些奇怪的胡子颜色背后的科学原理是什么呢?

What’s the science behind these curious beards, especially among men with dark, blond or even graying mops?

This follicular fluke hasn’t escaped the notice of researchers like Nina Jablonski, professor of anthropology at Penn State University, whose research has focused on the biology of hair hues. “I have observed many, especially younger, men with red beards and red hair and some with reddish beards and light brown, blond or red-blond hair,” she told Live Science.

这种现象引起了宾夕法尼亚州立大学人类学教授尼娜·雅布伦斯基等研究人员的注意,她的研究领域是在毛发颜色背后的生物学。尼娜说道:“我观察到许多男人,尤其是年轻人,他们的头发和胡子都是红色的,但还有一些胡子是红色的人却有着浅棕色、金色或红金色的头发。”。

Most redheads live in Celtic countries such as Scotland, Ireland and Wales, followed by England and the Nordic nations, according to The Telegraph. Perhaps predictably, these red tresses exist because of a genetic mutation. Specifically, a mutation in a gene known as “MC1R,” which controls pigment production in hair cells, among other things such as fair skin, poor tanning ability and pain perception, which may explain why a local anesthetic is less effective for redheads.

据报道,大多数红头发的人生活在凯尔特国家,如苏格兰、爱尔兰和威尔士,其次则是英格兰和北欧国家。这些红色头发的存在是因为基因突变,具体来说,是一种名为“MC1R”的基因发生了突变,该基因控制毛发细胞中色素的产生,除此之外,皮肤白皙、容易被晒黑和疼痛感也与该基因有关,这也许可以解释为什么局部麻醉药对红头发的人不那么有效。

Hair color is determined by the ratio of two different pigments; eumelanin is responsible for black tones and pheomelanin causes red ones. People with black or dark brown hair will probably have only eumelanin, or at least it will be the dominant pigment. Blonds, meanwhile, have less of both types of pigment than their darker-haired and redheaded friends. And redheads, of course, have mostly pheomelanin.

头发的颜色是由两种不同色素的比例决定的,真黑素使头发呈黑色,褐黑素使头发呈红色。黑色或者深棕色头发的人毛发中可能只有真黑素,红色头发的人毛发中可能只有褐黑素,而金发女孩的毛发中这两种色素可能都很少。

One role of the MC1R gene is to code for a protein called melanocortin, whose job is to convert the red pigment into the black one. But if a person has a double mutation in this gene, its resulting proteins aren’t as effective, which lead to red locks.

So, what happens when a person has a red beard, paired with a brown head of hair? The answer has some curious genetics at play, according to Jablonski.

“This will almost certainly be due to the differential expression of MC1R in the follicles of beard hair versus scalp hair resulting in the production of a different mixture of dark brown eumelanin and yellow-red pheomelanin,” Jablonski said.

MC1R基因的一个作用是编码一种叫做黑皮质素的蛋白质,其任务是将褐黑素转化为真黑素。但是如果一个人的该基因发生了双重突变,那么其产生的蛋白质就不那么有效了,从而导致这人拥有一头红头发。但是为什么会有人胡子是红色,而头发是棕色呢?雅布伦斯基表示:“这是由于MC1R在胡须毛囊和头皮毛囊中的不同表达。”。

In other words, the same gene is behaving differently in different parts of the body and that’s probably because there’s just a single mutation of the MC1R gene, rather than a double mutation — meaning that the person is effectively a carrier of the redhead gene.

The phenomenon also occurs in some men as they age — usually as they pass their 40th birthday, which is probably because the pigment-producing cells in scalp hair and beard hair age at different rates, Jablonski said.

So you don’t have to be young and ginger to have a red beard, but it certainly helps.

换句话说,同一个基因在身体的不同部位表现不同,这可能是因为 MC1R 基因只发生了一次突变,而不是双重突变。雅布伦斯基表示,这种现象也发生在一些40岁以上的男性身上,这可能是因为头发和胡须中产生色素的细胞的年龄不同。

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