Anticipation 3
Anticipation 3
 
Custom Search
Anticipation 3
   
 
 
 
Accelerated Mobile Pages
Anticipation 3
Home Page

United Kingdom
United Kingdom
 
 
Go Back

Smartphone









Free the Animation VR / AR
Play to reveal 3D images and 3D models!
   
 
vlrPhone / vlrFilter
Project of very low consumption, radiation and bitrate softphones, with the support of the spatial audio, of the frequency shifts and of the ultrasonic communications / Multifunction Audio Filter with Remote Control!



 

Vectors and 3D Models

City Images, Travel Images, Safe Images

Howto - How To - Illustrated Answers

 

Anticipation (genetics)
In genetics, anticipation is a phenomenon whereby as a genetic disorder is passed on to the next generation, the symptoms of the genetic disorder become

View Wikipedia Article

function mfTempOpenSection(id){var block=document.getElementById("mf-section-"+id);block.className+=" open-block";block.previousSibling.className+=" open-block";}

In genetics, anticipation is a phenomenon whereby as a genetic disorder is passed on to the next generation, the symptoms of the genetic disorder become apparent at an earlier age with each generation. In most cases, an increase of severity of symptoms is also noted. Anticipation is common in trinucleotide repeat disorders, such as Huntington's disease and myotonic dystrophy, where a dynamic mutation in DNA occurs. All of these diseases have neurological symptoms. Prior to the understanding of the genetic mechanism for anticipation, it was debated whether anticipation was a true biological phenomenon or whether the earlier age of diagnosis was related to heightened awareness of disease symptoms within a family.

Contents
  • 1 Trinucleotide repeats and expansion
  • 2 Disease mechanisms
  • 3 Examples of diseases showing anticipation
  • 4 References
  • 5 External links

Trinucleotide repeats and expansion

Trinucleotide repeats are apparent in a number of loci in the human genome. They have been found in introns, exons and 5' or 3' UTR's. They consist of a pattern of three nucleotides (e.g. CGG) which is repeated a number of times. During meiosis, unstable repeats can undergo triplet expansion (see later section); in this case, the germ cells produced have a greater number of repeats than are found in the somatic tissues.

The mechanism behind the expansion of the triplet repeats is not well understood. One hypothesis is that the increasing number of repeats influence the overall shape of the DNA, which can have an effect on its interaction with DNA polymerase and thus the expression of the gene.

Disease mechanisms

For many of the loci, trinucleotide expansion is harmless, but in some areas expansion has detrimental effects that cause symptoms. When the trinucleotide repeat is present within the protein-coding region, the repeat expansion leads to production of a mutant protein with gain of function. This is the case for Huntington's disease, where the trinucleotide repeat encodes a long stretch of glutamine residues. When the repeat is present in an untranslated region, it could affect the expression of the gene in which the repeat is found (ex. fragile X) or many genes through a dominant negative effect (ex. myotonic dystrophy).

In order to have a deleterious effect, the number of repeats must cross a certain threshold. For example, normal individuals have between 5 and 30 CTG repeats within the 3' UTR of DMPK, the gene that is altered in myotonic dystrophy. If the number of repeats becomes greater than 50, the person is only mildly affected – perhaps having only cataracts. However, meiotic instability could result in a dynamic mutation that increases the number of repeats in offspring inheriting the mutant allele. Once the number of copies reaches over 100, the disease will manifest earlier in life (although the individual will still reach adulthood before the symptoms are evident) and the symptoms will be more severe – including electrical myotonia. As the number progresses upwards past 400, the symptoms show themselves during childhood or infancy.

Examples of diseases showing anticipation

Diseases showing anticipation include:

  • Autosomal dominant
    • Several spinocerebellar ataxias
    • Huntington's disease – CAG
    • Myotonic dystrophy – CTG
    • Dyskeratosis congenita – TTAGGG (telomere repeat sequence)
  • Autosomal recessive
    • Friedreich ataxia – GAA (Note: Friedreich ataxia does not usually exhibit anticipation because it is an autosomal recessive disorder.)
  • X-linked
    • Fragile X syndrome – CGG
  • Without expression type
    • Crohn's disease
    • Behçet's disease
References
  1. ^ Armanios, M., J. L. Chen, Y. P. Chang, R. A. Brodsky, A. Hawkins, C. A. Griffin, J. R. Eshleman, A. R. Cohen, A. Chakravarti, A. Hamosh, and C. W. Greider. 2005. Haploinsufficiency of telomerase reverse transcriptase leads to anticipation in autosomal dominant dyskeratosis congenita. Proc Natl Acad Sci U S A 102(44):15960-4.
  2. ^ Link text, NCBI Bookshelf: Friedreich Ataxia.
  3. ^ Polito, J.M.; Mendeloff, A.I; Harris, M.L; Bayless, T.M; Childs, Barton; Rees, R.C (23 March 1996). "Preliminary evidence for genetic anticipation in Crohn's disease". The Lancet. 347 (9004): 798–800. doi:10.1016/S0140-6736(96)90870-3. 
  4. ^ Fresko, I; M Soy; V Hamuryudan; S Yurdakul; Ş Yavuz; Z Tümerd; H Yazici (1998). "Genetic anticipation in Behçet's syndrome". Ann Rheum Dis. 57: 45–48. doi:10.1136/ard.57.1.45. 
External links
  • Genetic anticipation at the US National Library of Medicine Medical Subject Headings (MeSH)
  • v
  • t
  • e
Non-Mendelian inheritance: anticipation Trinucleotide Polyglutamine (PolyQ), CAG
  • Dentatorubral-pallidoluysian atrophy
  • Huntington's disease
  • Kennedy disease
  • Spinocerebellar ataxia 1, 2, 3, 6, 7, 17 (Machado-Joseph disease)
Non-polyglutamine
  • CGG (Fragile X syndrome)
  • GAA (Friedreich's ataxia)
  • CTG (Myotonic dystrophy type 1)
  • CTG (Spinocerebellar ataxia 8)
  • CAG (Spinocerebellar ataxia 12)
Tetranucleotide
  • CCTG (Myotonic dystrophy type 2)
Pentanucleotide
  • ATTCT (Spinocerebellar ataxia 10)


Amazon.com: TherMedic 3-in-1 Shoulder Wrap With Hot/Cold Therapy ...
Click on the image below to see the web page

Click Here to signal an inappropriate image

TherMedic 3-in-1 Shoulder Wrap ...
Amazon.com: TherMedic 3-in-1 Shoulder Wrap With Hot/Cold Therapy ...


Amazon.com: Harry Potter And The Prisoner Of Azkaban (Widescreen ...
Click on the image below to see the web page

Click Here to signal an inappropriate image

... Edition) (Harry Potter 3)
Amazon.com: Harry Potter And The Prisoner Of Azkaban (Widescreen ...


Stolen Memories (Witness Protection Book 3) - Kindle Edition By ...
Click on the image below to see the web page

Click Here to signal an inappropriate image

... Book 3) by [Johnson, Liz]
Stolen Memories (Witness Protection Book 3) - Kindle Edition By ...


Amazon.com: Into The Still Blue (Under The Never Sky Book 3) EBook ...
Click on the image below to see the web page

Click Here to signal an inappropriate image

... Sky Book 3) by [Rossi,
Amazon.com: Into The Still Blue (Under The Never Sky Book 3) EBook ...


The Beatles - The Beatles: 1+ - Amazon.com Music
Click on the image below to see the web page

Click Here to signal an inappropriate image

The Beatles - The Beatles: 1+ ...
The Beatles - The Beatles: 1+ - Amazon.com Music


Amazon.com: Mozart In The Jungle Season 3: Gael García Bernal ...
Click on the image below to see the web page

Click Here to signal an inappropriate image

... 3: Gael García Bernal, ...
Amazon.com: Mozart In The Jungle Season 3: Gael García Bernal ...


Amazon.com: AlleveRX- Pain Relief Cream & Inflammation Formula, 3 ...
Click on the image below to see the web page

Click Here to signal an inappropriate image

3 Oz: Health & Personal Care
Amazon.com: AlleveRX- Pain Relief Cream & Inflammation Formula, 3 ...


Amazon.com: Dungeon Siege III - PC: Video Games
Click on the image below to see the web page

Click Here to signal an inappropriate image

Amazon.com: Dungeon Siege III ...
Amazon.com: Dungeon Siege III - PC: Video Games


Amazon.com : Hydro Flow 100-Feet Roll Vinyl Tubing With 3/16-Inch ...
Click on the image below to see the web page

Click Here to signal an inappropriate image

... Tubing with 3/16-Inch ...
Amazon.com : Hydro Flow 100-Feet Roll Vinyl Tubing With 3/16-Inch ...


Amazon.com : Toshiba Camileo P100 HD Camcorder With 5x Optical ...
Click on the image below to see the web page

Click Here to signal an inappropriate image

... 5x Optical Zoom and 3-Inch ...
Amazon.com : Toshiba Camileo P100 HD Camcorder With 5x Optical ...


Twitter
 
Facebook
 
LinkedIn
 
 

 
 

WhmSoft Moblog
Copyright (C) 2006-2017 WhmSoft
All Rights Reserved