Chromosomes contain DNA and proteins. During cell division, the DNA is copied and organized into chromosomes. Mitosis produces identical daughter cells while meiosis reduces the chromosome number by half to produce gametes. Meiosis involves two cell divisions, resulting in four haploid cells. Genetic recombination occurs during meiosis, increasing genetic variation in offspring.
This presentation explains the topic of CELL CYCLE and CELL DIVISION.
It includes cell mitosis of both Plant cell and Animal cell with labelled diagrams.
It is the presentation on the MEIOSIS phase of the Cell division.
It includes all the details and definitions that are related to the topic of meiosis with the labelled diagrams.
If you have any query or a question, you may ask in the comment box.
thanks.
This presentation explains the topic of CELL CYCLE and CELL DIVISION.
It includes cell mitosis of both Plant cell and Animal cell with labelled diagrams.
It is the presentation on the MEIOSIS phase of the Cell division.
It includes all the details and definitions that are related to the topic of meiosis with the labelled diagrams.
If you have any query or a question, you may ask in the comment box.
thanks.
The slides contain all about meiosis. in this slides i collected all information about meiosis. which is useful for everyone.
so watch these slides and comment for any problems.
thanks
Most relevant information about the cell, its discovery, types and various kinds of organelles and their function. it also focus on how molecules are transported across the cell membrane.
2018/2019
Continuation of the cell structure and function. This presentation highlights the cell cycle and concentrate on how cell division occur and the steps involved in cell dividing.
2018/2019
The slides contain all about meiosis. in this slides i collected all information about meiosis. which is useful for everyone.
so watch these slides and comment for any problems.
thanks
Most relevant information about the cell, its discovery, types and various kinds of organelles and their function. it also focus on how molecules are transported across the cell membrane.
2018/2019
Continuation of the cell structure and function. This presentation highlights the cell cycle and concentrate on how cell division occur and the steps involved in cell dividing.
2018/2019
2. Cell Reproduction
• As a cell prepares to divide, the DNA inside
the nucleus becomes organized into
chromosomes
• This is to ensure that both of the new cells get
all of the genetic information from the original
cell
4. Chromosome Structure
• Chromosomes consist
of 2 identical halves
called chromatids
– When a cell divides,
each of the two new
cells will receive one
chromatid
• Two chromatids are
attached at the
centromere
7. Chromosome Numbers
• Animal chromosomes are categorized as
either sex chromosomes or autosomes
– Sex chromosomes determine the sex of an
organism
• In humans, sex chromosomes are X or Y
(females = XX, males = XY)
– All of the other chromosomes are autosomes
8. Chromosome Numbers
• Every cell of an organism produced by sexual
reproduction has two copies of each
autosome (one from each parent)
• The two copies are called homologous
chromosomes
– Same size and shape and carry genes for the same
traits
10. Diploid and Haploid Cells
• Diploid – cells that have • Haploid – cells that only
2 sets of chromosomes have 1 set of
(46 total in humans) chromosomes (23 total
in humans)
• Only sperm and egg
cells are haploid
12. Cell Division in Prokaryotes
• Binary fission is the division of a prokaryotic
cell into two offspring cells
13. Cell Division in Eukaryotes
• Two types of cell division
– Mitosis results in new cells that are identical to
the original cell
– Meiosis occurs during the formation of gametes
(haploid reproductive cells)
14. The Cell Cycle
• A repeating set of
events in the life of a
cell
• Division is one phase of
the cycle
• Time between cell
divisions is called
interphase
15. Interphase
1. G1 phase – offspring cells grow to mature size
2. S phase – the cell’s DNA is copied
3. G2 phase – cell prepares for cell division
• Cells can exit the cycle and enter into the G0
phase to stop dividing (ex: fully developed
brain cells)
17. Prophase
• DNA condenses into
chromosomes
• Nuclear membrane
breaks down
• Centrosomes form and
microtubules grow from
them (called the mitotic
spindle)
18. Metaphase
• Chromosomes line up in
the middle of the cell
• Spindle fibers attach to
the centromere of each
chromosome
19. Anaphase
• Chromatids are pulled
apart and move to
opposite ends of the
cell
21. Cytokinesis
• Animal cells – • Plant cells – cell plate
cytoplasm divides in forms between new
two cells
22. Control of Cell Division
• A cell spends most of its time in interphase
• What tells the cells to exit interphase and
begin dividing?
• There are three main checkpoints that act as
“traffic signals” for the cell to divide or not to
divide
23. Control of Cell Division
1. Cell growth (G1)
checkpoint – controls
whether the cell will
divide
2. DNA synthesis (G2)
checkpoint – make
sure DNA was copied
properly
3. Mitosis checkpoint –
signals tell the cell to
exit mitosis
24. When Control Is Lost: Cancer
• If a mutation occurs in one of the genes that
regulates the cell cycle, cell growth and
division could be disrupted
• This disruption could lead to cancer – the
uncontrolled growth of cells
26. Meiosis
• A process of nuclear division that reduces the
number of chromosomes in new cells to half
the number in the original cell
27. Formation of Haploid Cells
• Meiosis produces gametes, which are haploid
reproductive cells
• Cells preparing to divide by meiosis undergo
the G1, S, and G2 phases of interphase
– Cells begin meiosis with a duplicate set of
chromosomes, just like mitosis
• Cells undergoing meiosis divide twice,
resulting in 4 haploid (1n) cells
28. Two Stages of Meiosis
• First cell division = Meiosis I
– Prophase I, Metaphase I, Anaphase I, Telophase I
and Cytokinesis I
• Second cell division = Meiosis II
– Prophase II, Metaphase II, Anaphase II, Telophase
II and Cytokinesis II
31. Prophase I
• DNA coils tightly into chromosomes
• Spindle fibers appear
• Nuclear membrane disassembles
• Synapsis occurs - homologous chromosomes
line up next to each other
– Each pair is called a tetrad
32. Prophase I
• Crossing-over occurs – portions of chromatids
may break off and attach to adjacent
chromatids
• Genetic recombination results – genetic
material between maternal and paternal
chromosomes is exchanged
34. Metaphase I
• Tetrads line up along
the middle of the cell
• Spindle fibers attach to
the centromere of each
homologous
chromosome
35. Anaphase I
• Each homologous
chromosome moves to
an opposite end of the
cell
• Random separation of
homologous
chromosomes is called
independent
assortment and results
in genetic variation
36. Telophase I and Cytokinesis I
• Chromosomes reach
opposite ends of the
cell and cytokinesis
begins
• Two new cells are
produced, each
containing one
chromosome from each
homologous pair
(haploid – 1n)
37. Prophase II
• Spindle fibers form and
begin to move the
chromosomes toward
the midline of the
dividing cell
40. Telophase II and Cytokinesis II
• Telophase II – nuclear
membrane forms
around the
chromosomes in each
of the four new cells
• Cytokinesis II – 4 new
cells are formed, each
with half of the original
cell’s number of
chromosomes
41. Development of Gametes
• In animals, the only
cells that divide by
meiosis are those that
produce gametes within
the reproductive organs
– In humans – testes
(males) and ovaries
(females)
42. Development of Gametes
SPERMATOGENESIS
• In the testes – male
gametes known as sperm
cells or spermatozoa are
produced
• One diploid cell divides
meiotically to form four
haploid cells called
spermatids – each
develops into a mature
sperm cells
43. Development of Gametes
OOGENESIS
• Production of mature egg
cells, or ova
• A diploid reproductive cell
divides meiotically to
produce one mature egg
cell (ovum) and three
polar bodies which will
degenerate – cytoplasm is
not evenly distributed in
cytokinesis
44. Sexual Reproduction
• Production of offspring through meiosis and
the union of a sperm and an egg
• Offspring are genetically different because
genes are combined in new ways
• Advantage: enables species to adapt rapidly to
new conditions