Unit 1 4ESO Bilingüe

1. CELL DIVISION

2. CELL DIVISION
2 stages = interphase (growth &
replication of DNA) AND mitotic
phase (division of cell into 2
daughter cells)

3. Interphase
 Divided into 3 phases:
 G1= small cell is absorbing nutrients, growing
and protein synthesis
 S = REPLICATION of DNA and histones.
Preparation for making duplicate cells during
mitosis.
 G2 =Preparation for cell division.

4. Mitotic Phase: division of the nucleus
 Equal distribution of 2 sets of chromosomes (DNA) into 2 identical daughter cells
 It is vital that an exact copy of the genetic information is transmitted to the daughter cells.
 Divided into 4 stages of Mitosis (division of the nucleus):
 Prophase
 Metaphase
 Anaphase
 Telophase
 Cytokinesis (division of the cytoplasm)
division of the nucleus

5. Prophase
 Chromatin condenses visible chromosomes
 Appear as sister chromatids held together by centromere
 Nuclear membrane dissolves and disappears
 The centrioles migrate to opposite poles & spindle fibers form between
them
centrioles

6. Metaphase
 Chromosomes line-up on along the middle of the cell
 Centromeres are attached to spindle microtubules
Spindle microtubules

7. Anaphase
 Centromeres divide o break, as a result, the two chromatids that make up
each chromosome separate into two.
 Spindle fibers contract
 Result = sister chromatids are pulled away from one another towards the poles
 Chromatids

8. Telophase
 The chromosomes have moved to the poles of the cell
 The mitotic spindle disappear
 Nuclear membranes form around the 2 new nuclei
 The chromatids change to chromatin
 The nucleolus reappears.

9. Cytokinesis
 The cytoplasm distributed equally between the 2 new cells
 In animals, a cleavage furrow forms from outside in
 In plants, a cell plate forms from inside out
PlantAnimal

10. What Mitosis Actually Looks Like

11. Why is this so important?
 The product of mitosis is 2 cells
 The daughter cells are identical to each other & to the mother cell
Mother
cell
Identical
daughter
cells

12. Mitosis and Meiosis
 Mitosis:
-division of somatic (body) cells
 Meiosis
-division of gametes (sex cells)

14. MEIOSIS
 Meiosis is a speciallized type of cell división which reduce the chromosome
number by half. This process ocurrs in all sexually reproducing.

15. Meiosis
 Sometimes cell division results in cells that aren´t
identical to the parent cell
 Meiosis is the process of cell divison when a diploid
cell with 2n chromosomes divides into 4 daguther
halpoid cells with n chormosomes
 Meiosis happens at some point during the life cycle
of most sexually reproductive organims.

16. Reduction división

17. Prophase I
the pairs of homologous chromosomes
exchange genetic material. This is called
crossing over

18.  In the metaphase, pairs of homologous chromosomes (not indivial
chromosomes) become attached to the spindle fibres.
 In the anaphase, complete chromosomes (not chromatids) are pulled to
each spindle pole.
 The telophase in meiosis is the same as for mitosis
At the end of the first división, there are two
daughter haploid nuclei that have n
chromosomes

19. Second division
The second división process of meiosis is normal mitosis.
In this división each chromosome splits into chromatids.
Each daughter cell receives one set of chromatids.
At the end of second división, the cytoplam divides and
créate two separate cells. This is the last event in the
process of meiosis

20.  In meiosis, DNA replication is followed by two rounds of cell division to
produce four daughter cells each with half the number of chromosomes
as the original parent cell. The two meiotic divisions are known as meiosis I
and meiosis II.
 Alter the two divisions of meiosis the cell results in four haploid reproductive
cells