color blindness..........

Discussion in 'Biology & Genetics' started by andrewking, Apr 23, 2007.

  1. andrewking Registered Member

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    Hi I am Andrews, I want to discuss about color blindness and mostly survey shows that males are suffering from color blindness and why color blindness is mostly prevalent on males. If any one know about color blindness reply me
    Thanks in advance
     
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  3. Dinosaur Rational Skeptic Valued Senior Member

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    I think the common types of color blindness are due to recessive genes on the X Chromosome. A normal female has two X Chromosomes, while a normal male has an X & a Y Chromosome.

    The details and odds are as follows.
    • A male cannot inherit color blindness from a color blind father. If the father contributes his X Chromosome to the child, it is a girl. The Y chromosome (resulting in a male child) does not carry the gene for color blindness.

    • If a woman’s father is color blind and the women is not, then the woman has one gene for color blindness. Regardless of her husband, any male child has a 50-50 chance of being color blind.

      If her husband is not color blind, her female children have no chance of being color blind.

      If her husband is color blind, her female children have a 50-50 chance of being color blind.

    • A woman with a color blind father and a color blind maternal grandfather has only a 50-50 chance of being color blind (as stated above).

    • If a woman is color blind, all of her sons will be color blind. Her daughters will not be color blind if her husband is not color blind.
    The above gives a clue indicating why males are more likely than females to be color blind.

    The same type of inheritance applies to various other traits including: Hemophilia, baldness, and (I think) left handedness.
     
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  5. Dinosaur Rational Skeptic Valued Senior Member

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    There was an interesting problem that confused some people for a while many years ago.

    A survey of school children in Scotland indicated that a larger than normal percentage of Catholic children had an uncommon type of color blindness.

    The obvious question was: What does being Catholic have to do with being color blind? A quick check of statistics from other countries indicated normal percentages for Catholics in other countries. That indicated that it was being Scot and Catholic.

    Somebody quickly realized that most Catholics in Scotland were descendants of Irish immigrants. A check of statistics in Ireland indicated that this type of color blindness was extremely rare in Ireland and also rarer than usual among Irish in countries other than Scotland. In spite of the statistics, the phenomenon had to be due to being Irish. Strange?

    Then the light dawned in somebody's mind. People with this form of color blindness could not tell the difference between blighted potatoes and normal potatoes. Such people used blighted potatoes as seed for next year's crop, resulting in a disastrous crop the next year. These were the first Irish to emigrate from Ireland due to the famine caused by the potato blight. Most of them went to Scotland, the most convenient country (England & Ireland were at odds even then).

    That first wave of Irish emigrants mostly went to Scotland and included almost all of those with this type of color blindness. This resulted in its being rarer than usual in Ireland, and higher than usual among Irish in Scotland. Later waves of Irish emigrants (without color blindness) went to the US and various countries other than Scotland, which already had more than its desired share of Irish.
     
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  7. andrewking Registered Member

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    Thanks for your reply....I need better information about it
     

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