Tiff
Forum Guru
Topics: 50
Posts: 505
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Probably really simple, but can someone please explain the difference between X-linked dominant diseases vs. X-linked recessive diseases. Do all X-linked diseases fall under both categories?
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| KHILADI420
Forum Newbie
Topics: 4
Posts: 36
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most of the X-linked recessive diseases are in first aid in biochem section. i think its either 11 or 12. X- linked dominant its only one or two.
1) vit D resistant rickets
2) Fragile X syndrome (but i am not sure about this because some books say its X-linked recessive some say its dominant.)
FOR THE EXPLANATION READ KAPLAN BIOCHEM SECTION 3 CHAPTER 1 ITS REALLY GOOD.
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| usmlesavvy
Forum Senior
Topics: 5
Posts: 122
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X-LINKED DOMINANT:
*NO MALE TO MALE TRANSMISSION , so X-linked(Males transmit their X chromosomes to their daughters...not to their sons, thus males can only transmit the defective X to their daughters)
*THE DISEASE APPEARS IN ALL GENERATION, so Dominant (an affected parent has to transmit the disease to some of their offsprings.In other words ,the disease doesnt skip generation if a person is affect either of his parents must be affected, in order to have transmitted the disease causing gene)
*BOTH MALES AND FEMALES WILL BE AFFECTED ( heterozygote females will be affected becoz only one defective X is required for the disease as its a dominat one)
X-LINKED RECESSIVE:
*NO MALE TO MALE TRANSMISSION. hence X-linked.
*THE DISEASE SKIPS GENERATION,hence Recessive ( An affected father transmits the defective X to his daughter who maybe heterozygous carrier, but this daughter is capable of transmitting the disease to her son.....i.e An affected father--->A phenotypically Normal daughter----->An affected son)
*MUCH MORE COMMON IN MALES(RARE IN FEMALES)
(Becoz females have 2 copies of X.....and males require only one copy of the mutated X to have the disease)
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| usmlesavvy
Forum Senior
Topics: 5
Posts: 122
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Guess that was a very long answer .....
The cut it short,
In XR Mostly MALES will be affected( Females rarely affected) whereas in XD Both MALES and FEMALES will be affected( in fact females will be twice as more likely to be affected )
In XR disease SKIPPS generation whereas in XD it is present in every generation
Do not confuse XD with Mitochondrial mode In mitochondrial mode both Males and females will be affected)All offsprings of affected females affected and NONE of the ofsprings of affected male will be affected!
___________________
How can you hesitate?Risk!Risk anything!care no more for the opinion of others,for those voices.Do the hardest thing on earth for you.Act for yourself.Face the truth.....
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| Tiff
Forum Guru
Topics: 50
Posts: 505
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Thanks. Still not sure why some overlap. 
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| paheli
It'sAllAboutGoodKarma
Topics: 150
Posts: 1,979
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Really good explanation there, savvy!
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