mash
Forum Fanatic
Topics: 147
Posts: 1,326
|
The effect of mutations in the SHOX gene would best be described as
Haploinsufficiency
Dominant negative
Autosomal recessive
Gain of function
X-linked recessive
___________________
I hear and I forget. I see and I remember. I do and I understand.
--Confucius
|
| Malaysian
Forum Guru
Topics: 28
Posts: 778
|
gain of function??
|
| dxtxpx
Forum Guru
Topics: 259
Posts: 1,233
|
haploinsufficency:
A situation in which the protein produced by a single copy of an otherwise normal gene is not sufficient to assure normal function.
|
| Malaysian
Forum Guru
Topics: 28
Posts: 778
|
thanx for the description however if the single gene copy is normal and not enough of protein is being produced how can that be the answer since in haploinsuffiency the gene is nornal....in the question given above the gene has been mutated.
Do you know whats dominant negative??
|
| dxtxpx
Forum Guru
Topics: 259
Posts: 1,233
|
http://dorakmt.tripod.com/genetics/notes05.html
In diseases caused by haploinsufficiency and dominant-negative mutations, a mutation in one copy of the gene may cause the disease phenotype despite having one copy still functional . In haploinsufficiency, remaining amount of normal protein is insufficient for physiological function; in dominant-negative mutation, the normal copy is rendered nonfunctional by the mutant copy. These mutations will cause an autosomal dominant inheritance pattern. Osteogenesis imperfecta is due to dominant-negative mutations in type I collagen gene (COL1A1) mutations. Similarly, aquaporin-2 gene (AQP2) has a dominant-negative effect in causing type II nephrogenic diabetes insidipus. Diseases caused by haploinsufficiency are characterized by the lack of a correlation between the severity of the genetic defect (for example, size of a deletion) and the phenotype. One example is Digeorge syndrome. Histone H2AX is a genomic caretaker that requires the function of both gene alleles for optimal protection against tumorigenesis. Therefore disruption of one allele causes genomic instability and tumour susceptibility due to haploinsufficiency . Other examples of haploinsufficiency include PAX6 gene on 11p causing aniridia type II / WAGR syndrome; PTEN gene on 10q23 Cowden Disease and several cancers; SHOX (short stature homeobox containing gene) causing short stature as a dominant phenotype ; GLI3 gene on 7p13 causing Greig cephalopolysyndactyly syndrome (GCPS), elastin (ELN) gene on 7q11.2 causing Williams-Beuren syndrome, and transferring receptor gene TFRC. The original Knudson's two-hit hypothesis suggesting loss of heterozygosity or homozygous deletion are the two hits required for the loss of tumour suppressor gene activity has now been extended to include haploinsufficiency as well as transcriptional silencing by DNA methylation of promoters that can disable tumour-suppressor genes .[/url][/u]
|
| Malaysian
Forum Guru
Topics: 28
Posts: 778
|
Thanks dxtpx.....it was informative and I learnt something new(is it part of USMLE syllabus though??).
|
| dxtxpx
Forum Guru
Topics: 259
Posts: 1,233
|
honestly i have no clue if this is important or even relevant for step1. i only looked it up cuz mash asked that question. i hope we dont get tested on such topics. 
|
| Malaysian
Forum Guru
Topics: 28
Posts: 778
|
well i wouldn't mind them asking this specific question though....but anything else like you said I hope they won't!!!!
|
|
| |
| | | | | | | | |
