cell reproduction 1
TRANSCRIPT
![Page 1: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/1.jpg)
How Cells Reproduce
Chapter 8
Part 1
![Page 2: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/2.jpg)
8.1 Impacts/IssuesHenrietta’s Immortal Cells
Runaway cell divisions killed Henrietta Lacks, but her cells live on in research laboratories
![Page 3: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/3.jpg)
Fig. 8-1a, p. 136
![Page 4: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/4.jpg)
Fig. 8-1b, p. 136
![Page 5: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/5.jpg)
Guide Questions
• Why do they call Henrietta’s cells immortal?
• How did they immortalize Henrietta?• Do you think Henrietta will still be alive at
this time because of this technology?• Do you think the Johns Hopkins Hospital
did the right thing? Why or why not?• Do you think they can still clone Henrietta
using HeLa cells?
![Page 6: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/6.jpg)
Video: Henrietta's immortal cells
![Page 7: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/7.jpg)
8.2 Multiplication by Division
A cell reproduces by dividing in two
Each descendant cell receives a full set of chromosomes and some cytoplasm
Nuclear division mechanisms partition chromosomes of a parent cell into new nuclei
The cytoplasm divides by a separate mechanism
![Page 8: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/8.jpg)
Divisions of a Fertilized Egg
Third division of an early frog embryo
![Page 9: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/9.jpg)
Two Methods of Nuclear Division: Mitosis
Mitosis • Nuclear division process that maintains the
chromosome number• Basis of body growth, tissue repair and
replacement in multicelled eukaryotes; also asexual reproduction in some plants, animals, fungi, and protists
![Page 10: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/10.jpg)
Two Methods of Nuclear Division: Meiosis
Meiosis • Nuclear division process that halves the
chromosome number • Basis of sexual reproduction in multicelled
eukaryotes; precedes the formation of gametes or sexual spores
![Page 11: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/11.jpg)
Comparison of Division Mechanisms
![Page 12: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/12.jpg)
8.3 The Life of a Cell
A cell cycle starts when a new cell forms, and ends when the cell reproduces
Cell cycle • A series of events from the time a cell forms until
its cytoplasm divides• Includes three phases: interphase, mitosis, and
cytoplasmic division
![Page 13: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/13.jpg)
Interphase
Most of a cell’s activities, including DNA replication, occur in interphase
Interphase • In a eukaryotic cell cycle, the interval between
mitotic divisions when a cell grows, roughly doubles the number of its cytoplasmic components, and replicates its DNA
![Page 14: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/14.jpg)
Three Stages of Interphase
G1• 1st interval (gap) of growth before DNA replication
S• Interval of synthesis (DNA replication)
G2• 2nd interval (gap) when the cell prepares to divide
![Page 15: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/15.jpg)
Controls of Cell Division
Different types of cells proceed through the cell cycle at different rates
Gene expression controls regulate the cell cycle at different points
Loss of cell cycle controls results in cancer
![Page 16: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/16.jpg)
Chromosomes During the Cell Cycle
Human body cells have 23 chromosome pairs
Except for male sex chromosomes, the chromosomes of each pair are homologous
Homologous • Two members of a pair of chromosomes with the
same length, shape, and genes
![Page 17: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/17.jpg)
Chromosomes During the Cell Cycle
Mitosis maintains the chromosome number• Each chromosome is duplicated• Each new cell receives identical chromosomes
![Page 18: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/18.jpg)
Fig. 8-4, p. 139
A An unduplicated pair of chromosomes in a cell in G1.
B By G2, each chromosome has been duplicated.
C Mitosis and cytoplasmic division package one copy of each chromosome into each of two new cells.
![Page 19: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/19.jpg)
C Mitosis and cytoplasmic division package one copy of each chromosome into each of two new cells.
Fig. 8-4, p. 139
A An unduplicated pair of chromosomes in a cell in G1.
B By G2, each chromosome has been duplicated.
Stepped Art
![Page 20: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/20.jpg)
Eukaryotic Cell Cycle
![Page 21: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/21.jpg)
Fig. 8-3, p. 138
mitosis ends, interphase begins
interphase ends, mitosis begins
12
3
4
56
![Page 22: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/22.jpg)
Animation: The cell cycle
![Page 23: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/23.jpg)
8.4 Mitosis
At the end of interphase, a cell’s duplicated chromosomes condense tightly in preparation for nuclear division (mitosis)• Each chromosome consists of two sister
chromatids
Mitosis has four stages: prophase, metaphase, anaphase, and telophase
![Page 24: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/24.jpg)
Prophase
Prophase • Chromosomes condense and spindle forms• Nuclear envelope breaks up• Spindle microtubules attach to chromosomes
Spindle • Dynamically assembled and disassembled array
of microtubules that moves chromosomes during nuclear division
![Page 25: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/25.jpg)
Metaphase
Metaphase • Duplicated homologous chromosomes line up at
the spindle equator (halfway between spindle poles)
• Sister chromatids begin to move apart toward opposite spindle poles
![Page 26: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/26.jpg)
Anaphase
Anaphase • Microtubules separate the sister chromatids of
each chromosome and pull them toward opposite spindle poles
• Each DNA molecule is now a separate chromosome
![Page 27: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/27.jpg)
Telophase
Telophase • Two clusters of chromosomes arrive at the
spindle poles and decondense; new nuclei form
End of mitosis• Nuclear envelopes form around the two clusters
of chromosomes, forming two new nuclei with the parental chromosome number
![Page 28: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/28.jpg)
Mitosis
![Page 29: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/29.jpg)
Fig. 8-5a, p. 140
![Page 30: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/30.jpg)
Fig. 8-5b, p. 141
![Page 31: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/31.jpg)
Fig. 8-5b (1), p. 141
![Page 32: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/32.jpg)
Fig. 8-5b (1), p. 141
centrosome
1 Early ProphaseMitosis begins. In the nucleus, the DNA begins to appear grainy as it organizes and condenses. The centrosome is duplicated.
![Page 33: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/33.jpg)
Fig. 8-5b (2), p. 141
![Page 34: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/34.jpg)
Fig. 8-5b (2), p. 141
2 Prophase The chromosomes become visible as distinct structures as they condense further. Microtubules assemble and move one of the two centrosomes to the opposite side of the nucleus, and the nuclear envelope breaks up.
![Page 35: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/35.jpg)
Fig. 8-5b (3), p. 141
![Page 36: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/36.jpg)
Fig. 8-5b (3), p. 141
pole pole3 Transition to MetaphaseThe nuclear envelope is gone, and the chromosomes are at their most condensed. Spindle microtubules assemble and attach sister chromatids to opposite spindle poles. microtubule of
spindle
![Page 37: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/37.jpg)
Fig. 8-5b (4), p. 141
![Page 38: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/38.jpg)
Fig. 8-5b (4), p. 141
4 MetaphaseAll of the chromosomes are aligned midway between the spindle poles. Microtubules attach each chromatid to one of the spindle poles, and its sister to the opposite pole.
![Page 39: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/39.jpg)
Fig. 8-5b (5), p. 141
![Page 40: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/40.jpg)
Fig. 8-5b (5), p. 141
5 Anaphase
Motor proteins moving along spindle microtubules drag the chromatids toward the spindle poles, and the sister chromatids separate. Each sister chromatid is now a separate chromosome.
![Page 41: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/41.jpg)
Fig. 8-5b (6), p. 141
![Page 42: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/42.jpg)
Fig. 8-5b (6), p. 141
6 TelophaseThe chromosomes reach the spindle poles and decondense. A nuclear envelope forms around each cluster. Mitosis is over.
![Page 43: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/43.jpg)
Animation: Mitosis-step-by-step
![Page 44: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/44.jpg)
Fig. 8-5b (6), p. 141
Stepped Art
6) TelophaseThe chromosomes reach the spindle poles and decondense. A nuclear envelope forms around each cluster. Mitosis is over.
centrosome 1) Early ProphaseMitosis begins. In the nucleus, the DNA begins to appear grainy as it organizes and condenses. The centrosome is duplicated.
2) Prophase The chromosomes become visible as distinct structures as they condense further. Microtubules assemble and move one of the two centrosomes to the opposite side of the nucleus, and the nuclear envelope breaks up.
pole pole 3) Transition to MetaphaseThe nuclear envelope is gone, and the chromosomes are at their most condensed. Spindle microtubules assemble and attach sister chromatids to opposite spindle poles.
microtubule of spindle
4) Metaphase All of the chromosomes are aligned midway between the spindle poles. Microtubules attach each chromatid to one of the spindle poles, and its sister to the opposite pole.
5) Anaphase Motor proteins moving along spindle microtubules drag the chromatids toward the spindle poles, and the sister chromatids separate. Each sister chromatid is now a separate chromosome.
![Page 45: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/45.jpg)
Animation: Spindle apparatus
![Page 46: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/46.jpg)
Animation: Mechanisms for chromosome movement
![Page 47: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/47.jpg)
3D Animation: Mitosis
![Page 48: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/48.jpg)
Animation: Mitosis
![Page 49: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/49.jpg)
8.5 Cytoplasmic Division Mechanisms
A cell’s cytoplasm usually divides after mitosis, forming two cells, each with its own nucleus
Mechanisms of cytoplasmic division differ between animal cells and plant cells
![Page 50: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/50.jpg)
Cytoplasmic Division in Animal Cells
In animal cells, a contractile ring pinches the cytoplasm in two
Contractile ring • Band of actin and myosin filaments that contracts
to form the cleavage furrow
Cleavage furrow • In a dividing animal cell, the indentation where
cytoplasmic division will occur
![Page 51: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/51.jpg)
Cytoplasmic Division of an Animal Cell
![Page 52: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/52.jpg)
Fig. 8-6a, p. 142
A After mitosis is completed, the spindle begins to disassemble.
![Page 53: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/53.jpg)
Fig. 8-6b, p. 142
B At the midpoint of the former spindle, a ring of actin and myosin filaments attached to the plasma membrane contracts.
![Page 54: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/54.jpg)
Fig. 8-6c, p. 142
C This contractile ring pulls the cell surface inward as it shrinks.
![Page 55: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/55.jpg)
Fig. 8-6d, p. 142
D The ring contracts until it pinches the cell in two.
![Page 56: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/56.jpg)
Animation: Cytoplasmic division
![Page 57: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/57.jpg)
Cytoplasmic Division in Plant Cells
In plant cells, a cell-plate forms midway between the spindle poles and partitions the cytoplasm when it connects to the parent cell wall
Cell plate • After nuclear division in a plant cell, a diskshaped
structure that forms a cross-wall between the two new nuclei
![Page 58: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/58.jpg)
Cytoplasmic Division of a Plant Cell
![Page 59: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/59.jpg)
Fig. 8-7a, p. 143
A The plane of division was established before mitosis began. Vesicles cluster here when mitosis ends.
![Page 60: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/60.jpg)
Fig. 8-7b, p. 143
![Page 61: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/61.jpg)
Fig. 8-7b, p. 143
cell plate forming
B As the vesicles fuse with each other, they form a cell plate along the plane of division.
![Page 62: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/62.jpg)
Fig. 8-7c, p. 143
C The cell plate expands outward along the plane of division. When it reaches the plasma membrane, it attaches to the membrane and partitions the cytoplasm.
![Page 63: Cell Reproduction 1](https://reader033.vdocuments.us/reader033/viewer/2022061105/543f318fafaf9ffb098b457a/html5/thumbnails/63.jpg)
Fig. 8-7d, p. 143
D The cell plate matures as two new cell walls that join with the parent cell wall, so each descendant cell becomes enclosed by its own cell wall.