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The karyotype is characteristic of each specie, and this name represents a complete set of chromosomes.
The karyotype was the name given to the preparation of a complete set of metaphase chromosomes sorted by length and centromere location.
Fig 1. Metaphase
Karyology is the study of sets of chromosomes or karyotypes
Fig 2. Normal Female karyogram
Chromosomes are depicted in the standard format the karyogram or idiogram, in pairs by size.
Each human being possesses a total of 23 chromosomes but since they make pairs queue total number is 2x23= 46.
Fig 3. Representation of a karyogram
The karyotype is important to study chromosomal aberrations (down syndrome), cellular function, taxonomic relationships, evolution relationships and many others.
Perform a karyotype:
Karyotype requires the collection of living cells and culture of these cells for 48 to 72 hours in the presence of a Mitogen usually phytohemagglutinin
Mitogen -small bioactive protein or peptide that induces a cell to begin cell division
Living cells are then arrested in metaphase with colcemid.
Colcemid -inhibits microtube formation stopping the cell division
Down Syndrome
Down syndrome, trisomy 21 is characterized by an abnormality in the karyotype with chromosome 21 presenting an extra copy.
Fig 4. Trisomy 21 Karyogram
This extrachromosomal DNA causes the intellectual disabilities and physical features characteristic of Down syndrome, which vary among individuals.
Was first fully described in 1866 by John Langdon Down and occurs in about 1 in 1,000 babies born each year
Fig 5. Down syndrome physical characteristics
Karyotypes | Biology for Non-Majors I. (2022). Lumenlearning.com. https://courses.lumenlearning.com/wm-nmbiology1/chapter/reading-karyotypes/
Karyotype. (2022). Genome.gov. https://www.genome.gov/genetics-glossary/Karyotype
Down Syndrome (Trisomy 21). (2022). Genome.gov. https://www.genome.gov/genetics-glossary/Down-Syndrome-Trisomy-21
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