Mitosis y meiosis para alumnos de 4º ESO

1. DNA: CHROMATIN AND CHROMOSOMES

2. DNA: CHROMATIN AND CHROMOSOMES

3. DIPLOID AND HAPLOID CELLS

4. MITOSIS

5. WHAT IS THE AIM?
To deliver the same genetic material to daughter cells during cell division.

6. TO DELIVER THE SAME GENETIC MATERIAL
1. DNA replication.
2. DNA organize forming chromosomes.
3. During mitosis chromatids are delivered to different daughter cells.

7. MITOSIS GENERAL SCHEME

8. MITOSIS: PHASES
INTERPHASE:
DNA replication.
Centriole replication
Chromatin in the nucleus.

9. MITOSIS: PHASES
PROPHASE:
Chromosomes (2 chromatids) can be seen in the nucleus.
Centrioles start forming mitotic spindle.

10. MITOSIS: PHASES
METAPHASE:
The nucleus disappear.
Mitotic spindle attaches to chromosomes centromere.
Chromosomes align in the centre of the cell

11. MITOSIS: PHASES
ANAPHASE:
Chromatids split up and are delivered by the mitotic spindle to separate poles of
the cell.

12. MITOSIS: PHASES
TELOPHASE:
New nuclei start forming around the chromosomes.
Chromosomes turn to chromatin.
Cytokinesis.

13. MEIOSIS

14. What are the aims?
To get haploid cells. GAMETES.
Each gamete is going to be genetically unique. This is possible because of the
genetic recombination or crossing over.
To get haploid cells from diploid cells two cell divisions are needed.

15. FIRST MEIOTIC DIVISION

16. PHASES: INTERPHASE I
DNA replication.
Centriole replication

17. PHASES: PROPHASE I
Chromosomes appear and form tetrads.
Random exchange of fragments (crossing over) or genetic recombination.
Nucleus starts disappearing and centrioles form meiotic spindle.

18. PHASES: METAPHASE I
Pairs of homologous chromosomes bond to the meiotic spindle.

19. PHASES: ANAPHASE I
Complete chromosomes are pulled to opposite cell poles thanks to the meiotic
spindle.
Chromosomes are genetically different after crossing over.

20. PHASES: TELOPHASE I

21. SECOND MEIOTIC DIVISION
After first meiotic division daughter cells have chromosomes with two
chromatids, so the second division split up the chromosomes to obtain
chromosomes with one chromatid.
Second meiotic division occurs following the same phases than mitosis but
without DNA replication.

22. SECOND MEIOTIC DIVISION

23. MEIOSIS GENERAL SCHEME

24. MEIOSIS GENERAL SCHEME