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* The chromosomes when organised as an image in sequence are called a karyogram or idiogram. | * The chromosomes when organised as an image in sequence are called a karyogram or idiogram. | ||
:'''Links:''' [[trisomy 21]] | [[:File:Trisomy21female.jpg|Image- T21 female karyotype]] | [[:File:Trisomy21male.jpg|Image- T21 male karyotype]] | [[:File:Human idiogram-chromosome 21.jpg|chromosome 21 idiogram]] | |||
===Chromosome 21=== | |||
* the smallest human chromosome | |||
* about 47 million base pair | |||
* about 1.5 % of the total DNA in cells | |||
* contains between 300 and 400 genes (of human estimated 20,000 to 25,000 total genes) | |||
* [[trisomy 21]] or Downs Syndrome - additional copy of this chromosome | |||
* partial monosomy 21 - missing segment of the chromosome in each cell | |||
* ring chromosome 21 - circular structure, occurs when there are two breaks in a chromosome and the ends of the chromosome then fuse together | |||
Revision as of 10:59, 9 May 2011
Trisomy 21 (Down Syndrome) Male Karyotype
Down syndrome or trisomy 21 is caused by nondisjunction of chromosome 21 in a parent who is chromosomally normal and is one of the most common chromosomal abnormalities in liveborn children. The frequency of trisomy 21 in the population is approximately 1 in 650 to 1,000 live births, in Australia between 1991-97 there were 2,358 Trisomy 21 (Down) infants.
- The normal human karyotypes contain 22 pairs of autosomal chromosomes and one pair of sex chromosomes.
- The karyotype is the characteristic chromosome complement as identified by staining and can only be identified during cell division when chromosomes are folded.
- The chromosomes when organised as an image in sequence are called a karyogram or idiogram.
- Links: trisomy 21 | Image- T21 female karyotype | Image- T21 male karyotype | chromosome 21 idiogram
Chromosome 21
- the smallest human chromosome
- about 47 million base pair
- about 1.5 % of the total DNA in cells
- contains between 300 and 400 genes (of human estimated 20,000 to 25,000 total genes)
- trisomy 21 or Downs Syndrome - additional copy of this chromosome
- partial monosomy 21 - missing segment of the chromosome in each cell
- ring chromosome 21 - circular structure, occurs when there are two breaks in a chromosome and the ends of the chromosome then fuse together
Image Source: UNSW Embryology http://embryology.med.unsw.edu.au/Defect/page21.htm
File history
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current | 16:19, 27 July 2009 | 480 × 284 (10 KB) | MarkHill (talk | contribs) | Down syndrome or trisomy 21 is caused by nondisjunction of chromosome 21 in a parent who is chromosomally normal and is one of the most common chromosomal abnormalities in liveborn children. The frequency of trisomy 21 in the population is approximately 1 |
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File usage
The following 18 pages use this file:
- 2009 Lecture 2
- 2010 BGD Practical 12 - Abnormalities
- 2010 Lecture 1
- 2010 Lecture 2
- 2011 Lab 12 - Abnormalities
- ANAT2341 Lab 12 - Abnormalities
- Abnormal Development - Genetic
- BGDA Practical 12 - Abnormalities
- Foundations Practical - Critical Periods
- Genetic risk maternal age
- Historic Embryology Vignette
- Lecture - 2011 Course Introduction
- Lecture - 2012 Course Introduction
- Lecture - 2013 Course Introduction
- Lecture - Fertilization
- Trisomy 21
- Talk:2010 BGD Tutorial - Applied Embryology and Teratology
- Template:Trisomy 21 Vignette