Download Do Now

“Do Now”
 Take out a sheet of paper and answer the following
questions:
1.
2.
Distinguish between chromatin, chromatids, and
chromosomes.
What is the difference between offspring of a sexually
reproduced cell compared to the offspring of an
asexually produced cell?
The Cell Cycle
 Sequence of growth & division of a cell
 Interphase: period of cell growth
 longest phase
 DNA is duplicated in preparation for division
The Cell Cycle
 Work this problem in your notes:
 If the cell cycle in humans is 20 hours, how many cells
will exist after 1 week (168 hrs)?
Cell Division: “Mitosis”
 4 phases:
1. Prophase
2. Metaphase
3. Anaphase
4. Telophase
 Formation of 2
daughter cells

(each has complete
set of chromosomes)
st
1
Phase: Prophase
 Nuclear envelope
disintegrates
 Chromatin condenses
into chromosomes
 Centrioles migrate to
opposite ends of cell
 Spindle fibers begin to
form
nd
2
Phase: Metaphase
 Chromosomes attach to
spindle fibers by
centriole
 Chromosomes line up at
equator of cell
rd
3
Phase: Anaphase
 Separation of sister
chromatids
 Centromeres split apart
th
4
Phase: Telophase
 Chromatids reach
opposite ends of cell
 Chromosomes start to
unwind
 Spindle fibers break
down
 Nuclear envelope
reappears
Cytokinesis
 Cytoplasm divides
 Animal cells:
 Plasma membrane
pinches in at equator
 Cell is separated
 Plant cells:
 Cell plate laid down
across equator
 Cell membrane forms
around each cell
Onion Root Mitosis Exercise
 Maximum of 3 students
per group
 Pick up one biology book
per group
 Page 214-215
 Things to remember:
1. Start focus on low power
2. Orientation of slide
3. Get hypothesis approved
before making chart
4. Answer the “Analyze and
Conclude” section in
your notebook
“Ticket Out”
 Take out a sheet of paper and answer the following
questions in complete sentences:
At one time, interphase was referred to as the resting
phase of the cell cycle. Why do you think this
description is no longer used?
2. Why is it necessary for a cell’s chromosomes to be
distributed to its daughter cells in such a precise
manner?
1.