| From: erry ® | 04/02/2001
18:55:31 |
| Subject: Albino child |
post id:
221504 |
| Today while i was at work, a
young girl, i'm guessing about 1.5 or 2, came into the shop with her
mother - who was a relatively "normal" anglo saxon woman. The girl was
albino - white hair, white skin, red eyes. Three questions: 1. Do her eyes appear red because of the blood in her eye, and there is no pigment to cover it, hence it shows thru as pinky-red? 2. We often ask parents if their children are allowed a jellybean when they buy books. This girl was allowed one, as long as it was white - her mother explained that other colours stain her skin. How/why does this happen? 3. What causes "albinility"? I'm guessing genes .. | |
| From: dr drake | 04/02/2001
22:08:41 |
| Subject: re: Albino child |
post id:
221642 |
| Answer to number 3. - albinism is
caused by a single recessive gene, meaning that both parents of an albino
person or animal have to be carrying the gene. To be born albino you would
need to have both copies of the recessive gene. The parents can be normal - having one dominant normal skin colour gene and one recessive albino gene. If both parents are like this then there is a 25% chance of having an albino child. If both parents were albino then all their children would be albino. | |
| From: Di (Avatar) | 04/02/2001
22:29:09 |
| Subject: re: Albino child |
post id:
221653 |
| A question about question
2. Did the mother mean that eating it changed the childs skin, or touching it? | |
| From: sissy | 04/02/2001
22:33:24 |
| Subject: re: Albino child |
post id:
221659 |
| I'm guessing that the child's
skin would be so very pale and fragile, that any dyes in the jelly beans
would stain her skin and be hard to remove, rather like spilling coloured
food or drinks on a beautiful white garment. I may be wrong, but I can't see how eating a jellybean would cause the child to change colour. However, as I said this is a guess. | |
| From: Daniel (illuminati) ® | 04/02/2001
22:38:01 |
| Subject: re: Albino child |
post id:
221664 |
| It would be interesting, though,
if the kid did change colour every time he/she ate a jellybean...that'd
adsd a whole new dimension to fashion! Blue one day, Green the next, then
purple...or he/she could dye him/herself a 'normal' skin colour with the
right jellybeans :) | |
| From: J.F. ® | 04/02/2001
23:25:05 |
| Subject: re: Albino child |
post id:
221692 |
| Erry, albinism results from
mutations that inactivate the melanin- synthesis genes, so there is no
melanin in eyes, skin or hair. For some reason, there is often a severe
defect of vision, too. I went to a lunch time seminar several years ago, where the doctor commented that many albinos were eligible for blind pensions in one country (I think it was UK) but eligible for driver's licences elsewhere (I think it was USA) He mentioned something about some albinos having a very little hair pigment, but it is too long ago to recall it well. I think he also commented that they do not have the area of high visual acuity on the retina (fovea) that other people have. I saw an albino woman shopping for clothing once; she held the price tags very close to one eye to see them. | |
| From: J.F. ® | 05/02/2001
23:20:37 |
| Subject: re: Albino child |
post id:
222631 |
| Plenty of info on albinism
here: http://cdr.lightsmithproductions.com/albinism.html "Oculocutaneous (pronounced Ock-you-low-kew-Tain-ee-us) albinism involves the eyes, hair, and skin. Ocular albinism involves primarily the eye. People with ocular albinism may have slight lightening of hair and skin colors as well, compared to other family members. At present researchers have defined 10 different types of oculocutaneous albinism, and five types of ocular albinism, on the basis of their appearance by clinical examination. Newer laboratory research studying DNA has shown that there are numerous types of changes in the genes of those with albinism, including within families. Therefore, it is likely that the current system for naming types of albinism will change as research progresses." Because there are so many genes causing albinism, it is possible that two albino parents would be able to pass on working versions of all genes involved to produce pigmented offspring. "The most common types of oculocutaneous albinism are called "ty-negative" and "ty-positive". Persons with ty-neg albinism have no melanin pigmentation, and more difficulty with vision. Those with ty-pos albinism have very slight pigmentation, and generally less severe visual difficulties." They explain recessive autosomal albinism + also: "The above explanation of the inheritance of albinism does not apply to one type of ocular albinism, called X-linked ocular albinism. For X-linked inheritance, the gene for albinism is located on an X chromosome. Females have two X chromosomes, while males have one X chromosome and one Y chromosome. X-linked ocular albinism appears almost exclusively in males. The gene for it is passed from mothers who carry it to their sons. The mothers have subtle eye changes which an ophthalmologist could identify, but mothers generally have normal vision. For each son born to a mother who carries the gene, there is a one in two chance of having X-linked ocular albinism." "Eye conditions common in albinism include: Nystagmus, irregular rapid movement of the eyes back and forth. Strabismus, muscle imbalance of the eyes ("crossed eyes" or "lazy eye"), Sensitivity to bright light and glare. People with albinism may be either far-sighted or near-sighted, and often have astigmatism. " There is more good info on the site. As for the patched pigmentation on the man, I think that is analogous to the "merle" pattern in other species. I will check. | |
| From: J.F. ® | 05/02/2001
23:29:36 |
| Subject: re: Albino child |
post id:
222637 |
| http://www.blindbabies.org/factsheet_albinism.htm "CHARACTERISTICS Low Vision (visual acuity between 20/50 and 20/800) Sensitivity to bright light and glare (photophobia) Rhythmic, involuntary eye movements (nystagmus) Absent or decreased pigment in the skin and eye and sensitivity to sunburn (ultraviolet light) that could lead to skin cancers or cataracts in later life "Slowness to see" in infancy Farsighted, nearsighted, often with astigmatism Underdevelopment of the central retina (foveal hypoplasia) Decreased pigment in the retina (blonde fundus) Inability of the eyes to work together (absence of stereo vision) Misrouting of the nerve pathways from the retina to the brain Light colored eyes ranging from lavender to hazel, with the majority being blue Strabismus, with both vertical and horizontal deviations " I read years ago that Siamese cats were shown to have some misrouting of nerve pathways. I wonder if the ones that do not look crosseyed have that defect? Plenty of info on that site on how to help albinos see + cope in life, their special needs, etc. | |
| From: J.F. ® | 05/02/2001
23:46:49 |
| Subject: re: Albino child |
post id:
222659 |
| Sarah's Mum, it might be that the
patched man had a gene like "piebald" as this cat breeder calls it:
http://home.earthlink.net/~featherland/off/white.html There is a bit of basic embryology that may apply to humans as well as cats: "When an egg is first fertilized, all the cells are the same. This is followed by a process known as differentiation, where individual cells start to take on their unique "duties" in the complete animal. In this process, some cells start to move from the part of the embryo called the neural crest (at the top of what will be the kitten), down over the sides of the embryo towards the bottom. These cells will later further differentiate into cells responsible for many functions, including the melanocyte cells that give color to a cat's skin and fur. If these cells contain the genotype ww and no dominant alleles of the piebald gene they will travel all the way to the bottom of the embryo. If they contain one or two copies of the piebald gene, they can get "lazy" and stop before they complete the journey. If they have one or more copies of the epistatic white gene, this journey will be interfered with as well, stopping very shortly after it starts. Many factors can influence this "pigment parade". Some bicolors have perfectly symmetrical markings, some have their white "askew". Some have one well defined unfragmented area of white, others have color that seems to scatter across an area. This could be due to polygenes or even possibly what is surrounding the embryo as it develops. In a study of the effects of ultrasound on developing human babies no ill effects were found. However, they did find that more babies were lefthanded if they received ultrasound treatment prior to about 12 weeks. Science has a lot to explore in the field of embryology and environmental affects on developing cells! Can there be bad effects from stopping the parade of pigment forming cells prematurely? Yes, and this is what leads to deafness in some white cats and (very rarely) in "van" bicolors as well. As I stated earlier, these marching neural crest cells have more than one function to perform. Another type of cell can be formed from these neural crest cells that is essential for sound hearing. That is why deafness is most common in blue eyed white cats and when it occurs in vans, only in those with VERY little color. The pigment cells are responsible for giving our cats colored eyes as well as colored skin and fur. An eye without these cells is blue. If the pigment cells have marched down from the neural crest far enough to give the eyes color, chances are they have progressed far enough to provide sound hearing as well. But remember how some bicolors are assymetrical? The same thing can happen in whites, causing odd eyed cats or deafness in one ear. I have seen bicolored cats with eyes that are blue on the side towards the middle of the face and copper on the side towards the outside of the face. Now THAT is an odd-eyed cat! As breeding programs consistently produce bicolored and van cats with more and more white on them, blue and odd eyes will increase in frequency in these programs." Epistatic white is dominant (W), and the cat is white regardless of having genes for red or tabby etc. Polygenes are modifying genes, that slightly adjust the effects of major genes. Did the man you mentioned have hearing problems, even just in the ear on the white/ "albino" side? You cannot always tell unless such people mention it. | |
| From: J.F. ® | 06/02/2001
0:06:41 |
| Subject: re: Albino child |
post id:
222693 |
| A site on merle, white and
harlequin Great Danes, mentioning the high incidence of birth defects +
deafness: http://www.innercite.com/~daneaffr/ezcolor.htm "WHITES: "Double-merle" or dominant-whites result from harl x harl, harl x merle & merle x merle breedings (as well as when whites are bred to merles or harls). These dogs carry a double dose of the dominant gene that makes a harl/merle. They are usually 90% or more white, may have odd gray and/or black patches anywhere, and are commonly deaf, sometimes have eye defects, and can also be sterile & may have other problems. .... Many breeders require that all dogs who are white or near- white are culled at birth so as not to rear potentially defective puppies. Many of these whites (about ~50% of double-merle whites) die as embryos, reducing the size of the litter itself, & those who survive to birth must be expected to have serious defects. The common practice of ethical breeders is to humanely euthanize all near white pups at birth. " We can learn a lot about genetics from animal breeders. Culling humans is unacceptable, IMO. | |
| From: J.F. ® | 07/02/2001
20:48:44 |
| Subject: re: Albino child |
post id:
224757 |
| My Genetics lecturers estimated that on average, humans have 5 or 6 faulty genes each. I think they were overly - optimistic, and we may carry more. You are lucky if none of them cause noticeable problems. | |