Transcript Mitosis Lecture

Cell Replication
Prokaryotes
Binary Fission is
how prokaryotic
cells (bacteria) copy
themselves.
The DNA copies
and separates, and
the cell wall splits
the cell in half.
In Eukaryotic cells,
it’s more complicated…
• One section of DNA is called a gene.
– All cells within one organism have the same genes.
– What makes one cell different from another cell is that
different genes are turned on or off in different cells.
Mitosis
• Cells divide to make
more cells.
• The new cells made
during mitosis are called
daughter cells.
• DNA in a cell is bundled
into chromosomes.
• Humans have 46
chromosomes, 23 from
each parent. Every cell
has the same 46
chromosomes.
Chromosomes
• Chromosomes are bundles of DNA packaged around proteins.
• Each chromosome has a centromere in the center.
More Chromosomes
• Each half of the
chromosome is called a
chromatid.
• In mitosis, the two
chromatids of each
chromosome separate,
with each chromatid
going into a daughter cell.
Check for Understanding
Label the Parts of the Chromosome
• Use your notes
from the last two
slides to label this
picture:
Prophase
• In prophase, the DNA
condenses into
chromosomes and the
nuclear membrane
starts to disappear.
Metaphase
• In Metaphase, the
chromosomes line
up in the middle of
the cell.
Anaphase
• In anaphase, the
chromatids are
pulled apart to
opposite sides of
the cell.
Telophase
• In telophase the
spindle dissolves and
the nuclear
membranes reforms.
• The cytoplasm and
other cell organelles
are divided up.
Cytokinesis
• In Cytokinesis, the
cell membrane
pinches apart to
form two separate
cells.
Machinery of Mitosis
• The centrioles in the
cell attach spindle
fibers to the
centrosomes on the
chromosomes.
• The spindle fibers pull
the sister chromatids
apart, putting one
chromatid on each
side of the cell.
Check for Understanding
•
Prophase:
•
•
•
•
•
Chromosomes condense
Nuclear envelope disappears
centrosomes move to opposite sides of the cell
Spindle forms and attaches to centromeres on the chromosomes
Metaphase
• Chromosomes lined up on equator of spindle
• centrosomes at opposite ends of cell
•
Anaphase
• Centromeres divide: the 2 chromatids of each chromosome are
split apart
• These chromatids are pulled to opposite poles by the spindle
•
Telophase
• Chromosomes de-condense
• Nuclear envelope reappears
• Cytokinesis: the cytoplasm is divided into 2 cells