Download Cell Processes

Cell Processes
Mitosis and Meiosis
Cell Cycle
• The cell cycle is a regular
sequence of growth and
division that cells undergo.
Stage 1: Interphase
• Cells grow to its full size
• Make an exact copy of its DNA
– DNA is found in chromatin
• Centrioles are also copied
• Prepare to divide into two cells
Stage 2: Mitosis
• Division of cytoplasm into
two new (daughter) cells
• Mitosis is divided into 4 parts
–Prophase
–Metaphase
–Anaphase
–Telophase
The Cell Cycle
Prophase– chromatin condense to form chromosomes.
– Pairs of centrioles move to opposite side of
the nucleus.
– Spindle fibers form a bridge between the
ends of the cell.
– The nuclear envelope breaks down.
The Cell Cycle
Metaphase–Chromosomes line up across the center
of the cell.
–Chromosome attaches to a spindle fiber
at its centromere
The Cell Cycle
Anaphase
– Centromeres split.
– The two chromatids separate and each
chromatid becomes a new chromosome.
– The new chromosome move to opposite ends.
– The cell stretches out as the opposite ends are
pushed apart.
The Cell Cycle
Telophase
– Chromosomes
begin to stretch
out and lose their
rod-like
appearance.
– A new nuclear
envelope forms
around each
region of the
chromosomes
Stage 3- Cytokinesis
– The cytoplasm
divides and the
organelles are
distributed into each
of the two cells.
The Cell Cycle
DNA
• DNA has four
kinds of nitrogen
bases:
– A (adenine)
– T (thymine)
– G (guanine)
– C (cytosine)
Only A and T pair
Only G and C pair
The Replication Process
• DNA replication begins when
the two sides of the DNA
molecule unwind and separate,
like a zipper unzipping.
• Next, nitrogen bases that are
floating in the nucleus pair up
with the bases on each half of
the DNA molecule.
• Once the new bases are
attached, a new DNA molecule
had formed.