robin082006
Forum Hero
Topics: 471
Posts: 5,125
|
X linked dominant, CGG repeat expansion
___________________
The Key to Succeed is Patience.
|
| mitty
Forum Guru
Topics: 52
Posts: 376
|
yes. Kaplan says it is x linked dominant but FA says autosomal recessive.
___________________
He will make it happen.
|
| nickriviera
Forum Newbie
Topics: 0
Posts: 4
|
Itīs definitively dominant! Itīs a classic example of both dominant and of rep expansion as well as Huntington.
|
| Geroo
Forum Guru
Topics: 114
Posts: 799
|
goljan says it's x linked recessive
|
| sonaliraj99
Forum Senior
Topics: 39
Posts: 132
|
HMMM.... i don't know wat d books mentioned above say... but i had a theory d moment i read d q.. i'l try it here..pl. do tel if its rt...
see... v say its phenotypic expression is in men.... they inherit it from ma... who doesn't ALWAYS express it.... cos she has 2 x.. so i think.. its recessive.. i'm REALLY REALLY SORRY if i'm confusin anyone.... i jus remembered d pedigree chart.. so d guess
___________________
ZIDDI.ZIDDI ARMAAN!!!ZIDDI.ZIDDI HAI TUFAAN.
ZIDDI.HUM BHI YAHA.
|
| sonaliraj99
Forum Senior
Topics: 39
Posts: 132
|
ANOTHER THING GUYS... ROBBINS SAYS ITS RECESSIVE
___________________
ZIDDI.ZIDDI ARMAAN!!!ZIDDI.ZIDDI HAI TUFAAN.
ZIDDI.HUM BHI YAHA.
|
| DrVirgo
Forum Hero
Topics: 1041
Posts: 3,342
|
I came here to ask the same question since I found contradicting statements regarding X linked dominant or recessive in different books. Can anyone look up in Harrisons or Merck? I don't have those right now.
Thanks.
Anyway:
First of all, X-linked means no Male to Male inheritance (because males give a Y to their sons)
X-linked dominant means that it can affect females as well as males since you only need ONE mutated X to have the disease.
X-linked recessive is more common in males becasue you have to have it on ALL your X chromosomes to have the disease. (Males only have one X, so its easier for them to get it. Females have 2, so its not likely they will get it).
___________________
Our greatest glory is not in never falling, but in rising every time we fall.
|
| pearljam59
Forum Guru
Topics: 120
Posts: 273
|
Actually FA 2006 just says X-linked.
|
| yasmeen
Forum Guru
Topics: 67
Posts: 936
|
its x linked dominant
|
| DrVirgo
Forum Hero
Topics: 1041
Posts: 3,342
|
Harrisons says X-Linked Recessive.
Lets just forget if its dominant or recessive, and remember that its X-Linked.
If its so uncertain and there are so many contradictions in various texts, the bad news is thats its frustrating for us, but the good news is that it doesn't make a good question for USMLE and will NEVER be asked.
___________________
Our greatest glory is not in never falling, but in rising every time we fall.
|
| paganini
Forum Senior
Topics: 26
Posts: 159
|
I had the same confusion a month ago. Kaplan lecture notes (2006-2007) of Biochemistry and Pathology says that Fragile X syndrome is X link dominant, Big mistake. Goljan, Robbins says X link recessive, BIG MISTAKE. BRS of pathology only says X-linked disorder, BIG MISTAKE. After reading many books, only 2 of them have good explanations: kaplan REVIEW volume I (2005), which is from a different author than that of the lecture notes; an Pathophysiology of disease (2005). Correct answer is to say that it follows a NONMENDELIAN INHERITANCE PATTERN. Fragile X syndrome is clearly a genetic disease, but fails to fallow the patterns for normal X-linked recessive or dominant mutation. Completely unaffected carrier males, called nonpenetrant transmitting males, may be identified in pedigrees (Kaplan Biochemistry lecture notes says: male have 100% penetrance, BIG MISTAKE). The male or famale offspring from such a carrier male are completely normal, but the grandchildren from the carrier's daughter may Be affected. Among these grandchildren aproximately 25% of the males will be affected, 25% will be unaffected carriers. Around 25% of the females may have mild symptoms of the disease, and about 25% of the females will be unaffected carriers. 50% of the grandchildren, both males and females, will be completely normal. A female carrier has an inheritance number of repeats, greater than 50 but less than 230. The promoter region is not hypermethylated, she has a premutation and is asymptomatic. If she has more than 230 repeats the promoter region is hypermethylated(the cause is unknown) and will manifest the symptoms. So is not x-recessive because you may have females affected. Is no x-dominant because males dont have complete penetrance. In some respect, fragile x syndrome is similar to other genetic conditions caused by X-linked mutations: Affected males are impaired more severely than females and is never transmitted from father to son. However it breaks the rule Of mendiluan transmission in that at least 20% of carriers males manifest NO signs of it, so we can not say it is X-linked.  What you should learn is that it is classified as a disorder with nonmendelian inheritance pattern.
___________________
Mr. Physiology. An answering machine.
|
| gpsbrar
Forum Elite
Topics: 34
Posts: 278
|
Paganini is right. It is non mendelian pattern of inheritence. Only think very important about it is Think Big (physical appearance) and low IQ. Linked to FMR 1 gene, X link and trinucleotide repeat expansion.
___________________
B+
|
|
| |
| | | | | | | | | | | | |
