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BELL WORK
Biology is the only science in which multiplication
means the same thing as division.
What do you think this statement means?
The Cell Cycle pg. 86
By the end of this presentation you should be able to:
1. Explain how cells produce more cells.
2. Describe the process of mitosis.
3. Explain how cell division differs in plants and animals.
The Life of a Cell
Cell Cycle- the life cycle of a cell.
- Starts when the cell is formed.
- Ends when the cell divides and forms new cells.
Deoxyribonucleic Acid
 DNA – the hereditary material that controls all cell
activities.
- Before a cell divides it MUST make a copy of its DNA
Chromosomes
 Chromosomes in eukaryotes
- Are one of the structures in the nucleus that are made
up of DNA and protein.
 Chromosomes in prokaryotes
- Is the main ring of DNA.
Copying chromosomes ensures that
each new cell will be an EXACT copy of
the cell that made it.
How does a cell make more cells?
- Prokaryotes make more cells through a process called
binary fission.
- Eukaryotes make more cells through a process called
mitosis.
Binary Fission and Prokaryotes
 Binary fission – cell division that occurs in bacteria
 Means “splitting into two parts.”
Binary Fission
Mitosis and Eukaryotes
 Different numbers of chromosomes
-Humans have 46 chromosomes, potatoes have 48
chromosomes, and fruit flies have 8 chromosomes.
 Chromosomes come in pairs called HOMOLOGOUS
CHROMOSOMES.
 Homologous chromosomes- have the same sequence of
genes and the same structure.
Mitosis and Eukaryotes
 People have 23 pairs of chromosomes to total 46 (23
chromosomes from MOM and 23 chromosomes from
DAD).
Question:
1. Potatoes have 48 chromosomes. How many came
from “MOM” and how many came from “DAD”?
2. Fruit flies have 8 chromosomes. How many came
from “MOM” and how many came from “DAD”?
Mitosis and Eukaryotes
- Eukaryotic cell cycle = 3 stages
Interphase
2. Mitosis
3. Cytokinesis – the division of the cytoplasm.
1.
Interphase
 The phase where chromosomes are copied.
Mitosis
 Mitosis has stages of its own
Prophase
2. Metaphase
3. Anaphase
4. Telophase
1.
Mitosis - Prophase
 Chromosomes condense (get smaller) and become
rodlike structures.
Mitosis- Metaphase
 The nuclear membrane is dissolved.
 Paired Chromatids line up in the middle of the cell.
What’s a chromatid?
Mitosis – Anaphase
 The chromatids separate and move to opposite sides of
the cell.
Mitosis- Telophase
 A nuclear membrane forms around each set of
chromosomes.
 The chromosomes unwind.
 Mitosis is complete!
Cytokinesis
 In cells that lack a cell wall, the cell pinches in two.
 In cell that have a cell wall, a cell plate forms between
the two new cells.
 At the end of cytokinesis, there are two separate cells.
How to remember the stages of
Mitosis…..
 Just think
P
M
A
T
PMAT
Answer these Questions
Do more complex organisms always have more
chromosomes than simpler organisms?
2. What is the difference between cytokinesis in an
animal cell and cytokinesis in a plant cell?
3. Now do the section review on page 89.
- No, you don’t have to write the questions.
1.