1. Chromosomes

2. Prokaryotic chromosomes
The prokaryotic DNA (bacterias) is a molecule, a circular chromosome, floating freely in the cytoplasm and without nuclear membrane.

3. Eukaryotic chromosomes
The eukaryotic chromosomes contain the genetic information in all eukaryotic
Mainly all the eukaryotic organisms have between 10 and 50 chromosomes in their body cells.
The human cells have 46 chromosomes (23 identical pairs).

4. ¿Do all the living thins have the same number of chromosomes??
No. Each species have a characteristic chromosomes number. For example:

5. Eukaryotic chromosomes
Each chromosome is made up of an only DNA molecule, strongly twisted around.
Chromosomes can’t be seen when the cell is not dividing. At that moment we call it chromatin.

6. Chromosomes in division cells
Each chromosome is composed of two sister chromatids, which are attached at a central point, the centromere.
Sister chromatids

7. Elements of the chromosomes

8. centromers
Sister chromatids

10. Kinetochore Chromatid
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Metaphase
chromosome
Kinetochore
microtubules
Centromere
region of
Chromatid

11. Different types of chromosomes according the centromere:

12. Karyotipe of a human being

13. Karyotipe
The set of chromosomes ordered according to their size and the position of their centromeres.
First 22 pairs are called autosomes.
The last pair is the sex chromosomes.
XX female and XY male.

14. The Y chromosome decision
Boy or girl?
The Y chromosome decision
Y - Chromosome
X - Chromosome

15. Woman karyotipe
XX decide female sex

16. Men karyotipe
XY decide male sex

17. Changes in the karyotipe
This karyotipe have 3 number 21chromosomes. This disorder is characterystic of Down syndrome (trysomy 21).