Download 1_Intro_Cycle_Replication_Chromosome

Cell Cycle
= the life cycle of a dividing cell
The Life of a Cell…
Let’s predict some things that a cell
does during its lifetime.
1 - Cells spend most of their time
making proteins that enable them to
do their specific job.
What is the process that makes
proteins?
The Life of a Cell…
Let’s predict some things that a cell
does during its lifetime.
2 - Each time a cell dies, it is
replaced.
The Life of a Cell…
Let’s predict some things that a cell
does during its lifetime.
3 - New cells have the same
amount of DNA as old cells.
The Life of a Cell…
Let’s predict some things that a cell
does during its lifetime.
4 - DNA is usually very stringy and
disorganized. What does it need
to do before a cell divides so that
each new cell gets a complete
copy?
The Life of a Cell…
Let’s predict some things that a cell
does during its lifetime.
5 - Older cells tend to be larger
than younger cells.
cell does its specific job
makes proteins - gene expression
Make more
organelles
Grows in
size
DNA
replication
Grows in
size
cytoplasm
divides into
two new cells
nucleus and
chromosomes divide
DNA organizes itself
into chromosomes
Two main phases:
Three phases in
interphase:
Two parts of cell
division:
Overview of the Cell Cycle - http://www.cellsalive.com/cell_cycle.htm
ZOOMING IN
DNA Replication
DNA copies itself in the
form of ______.
DNA replication occurs in
the _____phase of the cell
cycle.
DNA Replication
DNA strands separate. Complementary
bases are added to each half.
DNA Replication
RESULT:
Two ____________ strands of DNA.
DNA Replication
Important because……
each new cell
can get a complete copy
of the DNA!
DNA Replication
Semi-conservative:
Each of the new DNA molecules has
kept one half of the original DNA strand
Oops….there’s a mistake
•During DNA Replication about 1 error
per 1 billion bases happens.
•Proofreading enzymes check for
mistakes during DNA replication.
• Error = mutation
•Mutations happen when an error occurs
during DNA replication.
How is DNA replication
different from transcription
in gene expression?
-Transcription is when DNA is copied in the
form of RNA and is used by that same cell;
DNA replication is when DNA is copied in the
form of DNA so it can be used for the new
cell.
-Transcription happens in the G1 phase of
interphase, while DNA replication happens
during the S phase of interphase.
DNA gets organized…
Chromatin = uncoiled DNA
(INTERPHASE)
Packed into the nucleus
of every cell, there’s
nearly 6 feet of DNA!
DNA Coils into Chromosomes
During Cell
Division
(specifically
mitosis)- the DNA
gets organized
and coils into the
form of
CHROMOSOMES
DNA Coils into Chromosomes
Chromosome Structure
Chromosome Structure
Chromosome Number
What can you infer about chromosomes an
organism has and its complexity?
Extreme Chromosome Numbers
The record for minimum number of chromosomes
belongs to a subspecies of the ant Myrmecia
pilosula, in which females have a single pair of
chromosomes. This species reproduces by a process
called haplodiploidy, in which fertilized eggs become
females, while unfertilized eggs develop into males.
Hence, the males of this group of ants have, in each
of their cells, a single chromosome.
The record for maximum number of chromosomes
is found in found in the fern family, Ophioglossum
reticulatum. This fern has roughly 630 pairs of
chromosomes or 1260 chromosomes per cell.