How are men more likely to be color blind than women?

Question

This is a homework question, explaning something about the (X,Y) and the (X,X) chromosomes. Please Help!

Answer 1

What colorblindness is:
Color blindness (color vision deficiency) is a condition in which certain colors cannot be distinguished, and is most commonly due to an inherited condition. Red/Green color blindness is by far the most common form, about 99%, and causes problems in distinguishing reds and greens. Another color deficiency Blue/Yellow also exists, but is rare and there is no commonly available test for it.
Depending on just which figures you believe, color blindness seems to occur in about 8% - 12% of males of European origin and about one-half of 1% of females. I did not find any figures for frequency in other races. Total color blindness (seeing in only shades of gray) is extremely rare.
There is no treatment for color blindness, nor is it usually the cause of any significant disability. However, it can be very frustrating for individuals affected by it. Those who are not color blind seem to have the misconception that color blindness means that a color blind person sees only in black and white or shades of gray. While this sort of condition is possible, it is extremely rare. Being color blind does keep one from performing certain jobs and makes others difficult.

Life's minor frustrations (and occasional dangers) for the color blind:
Weather forecasts - especially the Weather Channel - where certain colors just can not be distinguished on their weather maps. Also, maps in general because of the color coding on the legends.
Bi-color and tri-color LEDs (Light Emitting Diodes): Is that glowing indicator light red, yellow, or green?
Traffic lights, and worst of all, Caution lights: Color blind people always know the position of the colors on the traffic light - in most states, Red on top, Yellow in the center, Green (or is that blue?) on the bottom. It isn't good when we go to a city or state where they put traffic lights horizontal - it takes a couple of days to get used to that one! But caution lights present an entirely different problem. In this situation there is only one light; no top or bottom, no right or left, just one light that is either red or yellow - but which is it?
Getting in the sun with your girlfriend: So, you're out in the boat or on the beach with your girlfriend and soaking up the rays. But I can't tell until far too late if I'm getting red - or if she is. If I can tell it's red, by that time it's fire engine red and a painful sunburn is already present.
Color observation by others: "Look at those lovely pink flowers on that shrub". My reply, looking at a greenish shrub "What flowers?"
Purchasing clothing: I've got some really neat colors of clothes. Not everyone appreciates them like I do though; they seem to think the colors are strange. I just don't know why!
Kids and crayons: Color vision deficiencies bother affected children from the earliest years. At school, coloring can become a difficulty when one has to take the blue crayon -and not the pink one- to color the ocean.
Test strips for hard water, pH, swimming pools, etc.: A color blind person is generally unable to :
interpret some chemical reactions
see that litmus paper turns red by acid
identify a material by the color of its flame such as lead blue or potassium purple
interpret the chemical testing kits for swimming pool water, test strips for hard water, soil or water pH tests - all of which rely on subtle color differences and a band of similar colors to compare against.
Cooking and foods:
When cooking, red deficient individuals cannot tell whether their piece of meat is raw or well done. Many can not tell the difference between green and ripe tomatoes or between ketchup and chocolate syrup.
Some food can even look definitely disgusting to color deficient individuals. For example, people with a green deficiency cannot possibly eat spinach which to them just look like cow pat. They can however distinguish some citrus fruits. Oranges seem to be of a brighter yellow than that of lemons.
Are you wearing lipstick? Many color blind people cannot tell whether a woman is wearing lipstick or not. More difficult to handle for some is the inability to make the difference between a blue-eyed blonde and a green-eyed redhead.

Clinical information about color blindness:
Cones (color sensitive receptors) containing single visual pigments selective for red, green, and blue light, are present in the normal human eye. Disturbances of color vision will occur if the amount of pigment per cone is reduced or if one or more of the three cone systems are absent.
Although defective color vision may be acquired as a result of another eye disorder, the vast majority of color blind cases are hereditary - present at birth. The gene for this is carried in the X chromosome. Since males have an X-Y pairing and females have X-X, color blindness can occur much more easily in males and is typically passed to them by their mothers.
Color blindness is rooted in the chromosomal differences between males and females. Females may be carriers of color blindness, but males are more commonly affected.
Color blindness is a malfunction of the retina, which converts light energy into electircal energy that is then transmitted to the brain. This conversion is accomplished by two types of photoreceptor cells in the retina: rods and cones.
The cones are responsible for encoding color. Each cone contains structures or visual pigments sensitive to one of three wavelengths of light: red, green, and blue. Normal persons are able to match all colors of the spectrum by mixtures of only three fundamental color sensitivities. Hence, the huge variety of colors we perceive stems from the cone cells' response to different compositions of wavelengths of light.
Defects in color vision occur when one of the three cone cell color coding structures fails to function properly. One of the visual pigments may be present and functioning abnormally, or it may be absent altogether.
For practical purposes, all color-deficient individuals have varieties of red or green deficiency. Blue deficiencies are very rare. Color deficient patients are not completely red or green blind. Compared to persons with normal color vision, they have some trouble differentiating between certain colors, but the severity of the color deficiency is variable.
Color blindness is normally diagnosed through clinical testing. (See the Ishihara color test - the one most common test used) Although there is no treatment for color blindness, most color deficient persons compensate well for their defect and may even discover instances in which they can discern details and images that would escape normal-sighted persons. At one time the U.S. Army found that color blind persons can spot "camouflage" colors where those with normal color vision are fooled by it.




How color blindness works:

The human eye sees by light stimulating the retina (a neuro-membrane lining the inside back of the eye). The retina is made up of what are called Rods and Cones. The rods, located in the peripheral retina, give us our night vision, but can not distinguish color. Cones, located in the center of the retina (called the macula), are not much good at night but do let us perceive color during daylight conditions.
Many people think anyone labeled as "colorblind" only sees black and white - like watching a black and white movie or television. This is a big misconception and not true. It is extremely rare to be totally color blind. There are many different types and degrees of colorblindness, really they are "color deficiencies" since virtually no one is truly blind to all colors.
People with normal cones and color vision are able to see all the different colors and subtle mixtures of them by using cones sensitive to one of three wavelength of light - red, green, and blue.
A mild color deficiency is present when one or more of the three cones functions "poorly". A more severe color deficiency is present when one of the cones does not function at "all" or is missing.
Protanomaly (one out of 100 males):
Protanomaly is referred to as "red-weakness", an apt description of this form of color deficiency. Any redness seen in a color by a normal observer is seen more weakly by the protanomalous viewer, both in terms of its "coloring power" (saturation, or depth of color) and its brightness. Red, orange, yellow, yellow-green, and green, appear somewhat shifted in hue ("hue" is just another word for "color") towards green, and all appear paler than they do to the normal observer. The redness component that a normal observer sees in a violet or lavender color is so weakened for the protanomalous observer that he may fail to detect it, and therefore sees only the blue component. Hence, to him the color that normals call "violet" may look only like another shade of blue.
Under poor viewing conditions, such as when driving in dazzling sunlight or in rainy or foggy weather, it is easily possible for protanomalous individuals to mistake a blinking red traffic light from a blinking yellow or amber one, or to fail to distinguish a green traffic light from the various "white" lights in store fronts, signs, and street lights that line our streets. Do not let them adjust the color on the television, because it will look far to redish or violet for the rest of the family members.
Deuteranomaly (five out of 100 of males):
Let the deuteranomalous person adjust your television and he would add more green and subtract red. He is considered "green weak". Similar to the protanomalous person, he is poor at discriminating small differences in hues in the red, orange, yellow, green region of the spectrum. He makes errors in the naming of hues in this region because they appear somewhat shifted towards red for him - difficulty in distinguishing violet from blue.
From a practical stand point though, many protanomalous and deuteranomalous people breeze through life with very little difficulty doing tasks that require normal color vision. Some may not even be aware that their color perception is in any way different from normal. The only problem they have is passing a color vision test.
Dicromasy - can be divided into protanopia and deuteranopia (two out of 100 males):
These individuals normally know they have a color vision problem and it can effect their lives on a daily basis. They see no perceptible difference between red, orange, yellow, and green. All these colors that seem so different to the normal viewer appear to be the same color for this two percent of the population.
Protanopia (one out of 100 males):
For the protanope, the brightness of red, orange, and yellow is much reduced compared to normal. This dimming can be so pronounced that reds may be confused with black or dark gray, and red traffic lights may appear to be extinguished. They may learn to distinguish reds from yellows and from greens primarily on the basis of their apparent brightness or lightness, not on any perceptible hue difference. Violet, lavender, and purple are indistinguishable from various shades of blue because their reddish components are so dimmed as to be invisible e.g. Pink flowers, reflecting both red light and blue light, may appear just blue to the protanope.
Deuteranopia (one out of 100 males):
The deuteranope suffers the same hue discrimination problems as the protanope, but without the abnormal dimming. The names red, orange, yellow, and green really mean very little to him aside from being different names that every one else around him seems to be able to agree on. Similarly, violet, lavender, purple, and blue, seem to be too many names to use logically for hues that all look alike to him.

Answer 2

Because color blindness is a sex-linked trait. That means it is found on the X chromosome. It is also a recessive trait. So, females have two X chromosomes. If one of them has the color blindness trait, then it's okay, because females have a second X that probably won't have the color blindness trait on it. And, because color blindness is recessive, the X without colorblindness will be the one that is expressed. But, she could pass on that recessive X to her sons. And, if her son gets that X, he WILL be color bind, because he only has one X. The Y chromosome carries very little genetic information on it; so the male will be colorblind. The only way that a woman could be color blind would be if her father is colorblind, and her mother is a carrier. The chances of a colorblind man marrying a colorblind carrier woman isn't that high (colorblindness isn't that common in the first place), and even if that happens, the daughter would have to inherit the colorblind X from her mother, which is a fifty-fifty chance.

Answer 3

Alot more heres why:
Red-Green colorblindness is a sex-linked recessive trait which means it is carried on the X chromosome and is recessive. As you know, a normal male has one Y and one X chromosome while the female has 2 X chromosomes. Since the X chromosome is guaranteed from the mother, the son of a carrier (person who has gene for traits but dont physically have it) will show this trait.
Lets let X be dominant and Xr recessive (which carries color blindness)

For Female:
Since the female has 2 X chromosomes both have to be recessive in order to show color-blindness physically since if she only had one, the other dominant gene would mask it so she would have geneotype: Xr Xr and receive one from each parent

For Male:
Since he has only 1 X chromosome, at long as that X chromosome has the trait he will show it. The other chromosome he has is Y which can not mask the recessive X because they do not code for the same alleles. Thus his phenotype is: Xr Y

Therefore all males who have receieved the gene WILL show it but females will not show if she has 1 or less. only when she has 2 will this show. Also, the only way possible for a daughter to get color-blind is if she knows her father is colorblind (since the only X chromosome her father can give is Xr recessive) and the mother either shows the trait (Xr Xr) or is carrier (X Xr). The son receives his color-blind gene from the mother eiter carrier (X Xr) or showing the trait (Xr Xr) since the father gives him the Y chromosome.

Female: carrier (X Xr) x normal male(XY)

Offspring:
Xr X
Xr Y
XX
XY

here both girls dont show trait and only 1/2 are carrier
but boys half are normal and half show the trait

Answer 4

Men are more likely to suffer from red-green color blindness because the genes for the red and green color receptors are placed on the X chromosome, which men only have one of while women have two. It's a sex-linked trait, and the probability of a man having his one X chromosome defective in that way is higher than that of a woman having both her X chromosomes be defective.

Answer 5

colourblindness is an X-linked chromosomal disorder. Women have two X chromosomes (XX) and men have an X and Y (XY). This means that if you have a carrier or sufferer as a parent, if you are female, you probably would have a healthy X (one of your X choromosomes) which would dominate over it so you wouldn't show symptoms but a male only has a Y chromosome so if the X is infected the Y can't dominate over it and so they would display that phenotype.

Answer 6

The red and green color receptors are activated by dyes, which are encoded on the x chromosome (they are adjacent to each other). Since a male has only one of these, while a female has two, a fault in coding for the dyes will cause colorblindness in a male, but a female can use the coding from either x-chromosome to make the necessary dyes. So colorblindness among women is uncommon, although I know one who is. Of course, her sons are colorblind.

Answer 7

Men have XY chromosomes and women have XX chromosomes. The colorblind gene is located on the X chromosome.

For men, only one chromosome can have the gene. As soon as they have it, they're colorblind.
For women, there are two X chromosomes. If only one of them had the coloblind gene, the woman will carry the disease, but will not have any symptoms. If both X have the gene, then she will be colorblind.

This happens less often, because the woman would need to have a father colorblind and a mother who is at least a carrier, if not colorblind herself.

Answer 8

Color blind is having to do with genetics and color blindness is transmitted through X-Link Recessive where it only affects males. Most of the time mother is unaffected carrier and transmitted only to her sons, hence more males are affected than females.
I hope this helps!

Answer 9

The colour blindness gene is on the X chromosome. In women, if one of the X chromosomes has the colour blindness gene, the other normal gene can mask it, and the woman sees normally, but is a carrier for colour blindness. If both of her X chromosomes have the colour blindness gene, which is quite rare, then she will be colour blind.

In Men, since the only have one X chromosome, (the Y has no gene for seeing colour), then if he has the colour blindness gene on the X, there is no chance for it to be masked, and he will be colour blind.

Answer 10

Because the gene for colour vision is carried on the X chromosome. This means that women (who are XX) carry two copies of the gene while men (who are XY) only carry one copy.

When the gene is mutated to cause colour-blindness on one X chromosome it's effects are "masked" in women because they have a fully-functional gene on their other X chromosome but men only have one copy of the gene so if it is mutated then there is no other copy and the colour-blindness is expressed. This masking is called "Rececessiveness" - the gene is "Recessive".

Women can only be colour-blind through this type of mutation if both copies of the gene are mutated (one on each X chromosome - "double recessive"). This is more unlikely because it would require the pairing of a colour-blind man with a woman who was carrying at least one mutated copy of the gene.

Answer 11

1 out of 10 men are colorblind: 1 out of 100 women are colorblind