Transcript Still on cells…

Bellwork
STUDY FOR YOUR ORGANELLE
QUIZ!!!
 NO WORD BANK!
 STUDY DIAGRAM AND
FUNCTIONS!
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Quiz
Draw and label at least 5 parts of an
animal cell.
 Give the function for each below. 
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Still on cells…
The Cell Cycle
Cell Cycle
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Series of changes that a cell undergoes
from the time it forms until it divides
Check points throughout cycle determine if
the cell continues the cycle, stop dividing, or
die
Telomeres are “clocks” contained on
chromosomes that shorten with each
mitosis, and eventually cause the cell to
cease division
Interphase
Period in which a cell prepares for
division by growing and duplicating its
contents (so 2 cells can form from 1)
 Time of great synthetic activity
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Duplicates membranes, ribosomes,
lysosomes, and mitochondria
 Most importantly, it replicates its
genetic material
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Interphase cont.
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Considered in phases:
G1 phase: cell growth
 S phase: DNA replicated
 G2 phase: cell growth
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After the G2 phase, the cell enters into
mitosis
Cell Division
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Meiosis – makes sex cells (23
chromosomes each in humans)
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Chapter 19
The other kind of cell division
Mitosis – division of the nucleus,
increases cell numbers
 Cytokinesis – division of the
cytoplasm
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Mitosis - Prophase
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Chromosomes become visible in the
nucleus
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Each chromosome is composed of 2
identical portions (chromatids)
attached at the centromere
Centriole pairs move to opposite ends
of the cell
Prophase cont.
Nuclear envelope and nucleolus break
up
 Spindle fibers form from centrioles
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Mitosis - Metaphase
Chromosomes line up midway
between centrioles
 Spindle fibers attach to centromeres
of each chromosome
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One fiber from each pair of centrioles
is attached to each centromere
Mitosis - Anaphase
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Centromeres are pulled apart
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Chromosomes separate  individual
chromatids
Spindle fibers shorten and pull their
attached chromatids toward the
centrioles at opposite ends of the cell
Mitosis - Telophase
Chromosomes unwind
 Nuclear envelope forms around each
chromosome set
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Nucleoli appear within the newly
formed nuclei
Spindle dissolves
Telophase cont.
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Cytokinesis - begins during
anaphase when the cell membrane
starts to constrict down the middle of
the cell and cytoplasm divides
Mitosis and Cytokinesis
(Fig. 3.22)