3. DIPLOID CELLS
cells have pairs of
chromosomes
examples: skin cells,
muscle cells, red blood
cells, eye cells, etc.
4. HAPLOID CELLS
cells that do not have
pairs of chromosomes
only have half the
number of
chromosomes that
other cells have
example: sex cells -
sperm and egg
5. MEIOSIS AND SEX CELLS
Meiosis produces haploid sex cells
During meiosis, 2 divisions of the nucleus occur.
The division are called:
meiosis I
meiosis II
The steps have names like those in mitosis and are
numbered for the division in which they occur.
9. PROPHASE I
•In meiosis, each
duplicated
chromosome comes
near its similar
duplicated mate.
•In mitosis they do
not come near each
other.
10. METAPHASE I
In metaphase I, the pairs of
duplicated chromosomes
line up in the centre of the
cell.
The centromere becomes
attached to one spindle
fiber, so the chromatids do
not separate in anaphase I.
11. ANAPHASE I
In anaphase I, the two pairs of
chromatids of each similar pair
move away from each other to
opposite ends of the cell.
Each duplicated chromosome still
has two chromatids.
12. TELOPHASE I
In telophase I, the
cytoplasm divides, and
two new cells form.
Each new cell has one
duplicated chromosome
from each similar pair.
16. METAPHASE II
Duplicated chromosomes move to
the centre of the cell
Unlike what occurs in metaphase I,
each centromere now attaches to
two spindle fibers instead of one.
17. ANAPHASE II
The centromere divides and the
chromatids separate and move to
opposite ends of the cell.
Each chromatid now is an individual
chromosome.
18. TELOPHASE II
The spindle fibers
disappear.
A nuclear membrane forms.
When meiosis II is finished,
the cytoplasm divides.
19.
20. SUMMARY OF MEIOSIS
Meiosis I - 2 cells form
Meiosis II - 4 cells - which have half the number of
chromosomes
34. ant 2 turkey 82
cat 38 hermit crab 254
cow 60 goldfish 94
chicken 78 rabbit 44
kangaroo 12
mosquito 6
What species, out of every living
species, has the most chromosomes???
35. 2 0 0 es!!
1 oso m
ro m reticulatum
c h
ophioglossum
36. MISTAKES IN MEIOSIS
Mistakes are more common in plants than animal
cells.
If a mistake occurs in animal cells, sometimes the
zygote dies. If the zygote lives, every cell in that
organism will have the wrong amount of
chromosomes and may not grow normally.
