Genetics - Chromosome 21

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Introduction

21

Chromosome 21 is the smallest human chromosome consisting of about 47 million base pair, about 1.5 % of the total DNA in cells. The most common congenital chromosomal disorder is trisomy 21 or Downs Syndrome, resulting from an additional copy of this chromosome. (More? trisomy 21)


  • contains between 200 and 300 genes (of human estimated 20,000 to 25,000 total genes)
  • 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


Trisomy 21 Links: Trisomy 21 | Image T21 female karyotype | Image T21 male karyotype | chromosome 21 | Category:Trisomy 21 | Genetic Abnormalities | Prenatal Diagnosis


Nucleus structure cartoon 01.jpg Chromatin Structure.png
Chromosome territories (interphase) Chromosome (Chromatin) structure (mitosis)


Human Chromosomes: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | X | Y  

Some Recent Findings

  • Capturing a Long Look at Our Genetic Library[1] "Long-read sequencing, coupled to cDNA capture, provides an unrivaled view of the transcriptome of chromosome 21, revealing surprises about the splicing of long noncoding RNAs."


More recent papers  
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Search term: Chromosome 21

<pubmed limit=5>Chromosome 21</pubmed>

Development Genes

Idiogram (karyogram) - A drawing or photograph of the chromosomes of a particular cell.


Trisomy 21 Links: Trisomy 21 | Image T21 female karyotype | Image T21 male karyotype | chromosome 21 | Category:Trisomy 21 | Genetic Abnormalities | Prenatal Diagnosis

External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.


Human Chromosomes: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | X | Y  
Idiogram Chromosome Banding - The term refers to the light and dark pattern, seen after staining with a dye, of individual chromosomes identified in metaphase. It is only in meiosis and mitosis during metaphase that chromosomes can be easily identified, during the normal cell life (interphase) the chromosomes are unravelled and distributed within the nucleus in chromosome territories. A band is that part of a chromosome which is clearly distinguishable from nearby regions by appearing darker or brighter with one or more banding techniques.
Human Idiogram: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | X | Y
Genetic abnormality locations: 1-4 | 5-8 | 9-12 | 13-16 | 17-20 | 21-XY | sSMC
Inheritance Pattern images: Genetic Abnormalities | autosomal dominant | autosomal recessive | X-linked dominant (affected father) | X-Linked dominant (affected mother) | X-Linked recessive (affected father) | X-Linked recessive (carrier mother) | mitochondrial inheritance | Codominant inheritance | Genogram symbols | Genetics
Links: Genetics | Abnormal Development - Genetic

Cite this page: Hill, M.A. (2019, September 20) Embryology Genetics - Chromosome 21. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Genetics_-_Chromosome_21

What Links Here?
© Dr Mark Hill 2019, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
  1. Lagarde J & Johnson R. (2018). Capturing a Long Look at Our Genetic Library. Cell Syst , 6, 153-155. PMID: 29494803 DOI.