1. Continuity of Life: Cellular Reproduction
Chapter 11
Biology: Life on Earth (Audesirk)
Continuity of Life: Cellular Reproduction
Chapter 11

2. Biology: Life on Earth (Audesirk)
Binary Fission
Chapter 11
DNA replicated
Figure: 11.1
Title:
Prokaryotic cells divide by binary fission
Caption:
1) The circular DNA double helix attaches to the plasma membrane at one point. 2) The DNA replicates and the two DNA double helices attach to the plasma membrane at nearby points. 3) As the cell grows, new plasma membrane is added between the attachment points, pushing them further apart. 4) The plasma membrane grows inward at the middle of the cell. 5) The parent cell has divided into two daughter cells.
Membrane added
Chapter 11

3. Binary Fission 2
Chapter 11
constriction
fission

4. False-Color EM of Dividing Bacterium
Biology: Life on Earth (Audesirk)
False-Color EM of Dividing Bacterium
Chapter 11
Nuclear material
Division plane
Cell wall
Cytoplasm
Figure: 11.1a
Title:
Prokaryotic cells divide by binary fission
Caption:
1) The circular DNA double helix attaches to the plasma membrane at one point. 2) The DNA replicates and the two DNA double helices attach to the plasma membrane at nearby points. 3) As the cell grows, new plasma membrane is added between the attachment points, pushing them further apart. 4) The plasma membrane grows inward at the middle of the cell. 5) The parent cell has divided into two daughter cells.
Chapter 11

5. Biology: Life on Earth (Audesirk)
Functions of Mitosis
Chapter 11
Organs
Fertilized egg
(zygote)
Multicell stage
Mitotic cell division &
differ-entiation
Mitotic
cell division
Figure: 11.2
Title:
Mitotic cell division in eukaryotic cells produces cells needed for growth, development, and maintenance and repair
Caption:
Mitotic cell divisions produce the cells that make up the body of an embryo . Mitotic cell divisions continue to allow the embryo to grow, eventually, into an adult. (d) In the adult, mitotic cell divisions maintain tissues such as skin that are made of cells with short life spans.
Tissues
Chapter 11

6. Protozoa: Asexual Reproduction by Mitosis
Biology: Life on Earth (Audesirk)
Protozoa: Asexual Reproduction by Mitosis
Chapter 11
Figure: 11.3a
Title:
Mitotic cell division in eukaryotes enables asexual reproduction
Caption:
In unicellular microorganisms, such as the protist Tetrahymena, mitotic cell division produces two new, independent organisms.
New individuals
Chapter 11

7. Yeasts: Asexual Reproduction by Mitosis
Biology: Life on Earth (Audesirk)
Yeasts: Asexual Reproduction by Mitosis
Chapter 11
Budding
Nucleus divides by mitosis
Bud forms on cell
Nucleus moves into bud
Bud separates
Figure: 11.3b
Title:
Mitotic cell division in eukaryotes enables asexual reproduction
Caption:
Yeast, a unicellular fungus, reproduces by mitotic cell division.
Chapter 11

8. Hydra: Asexual Reproduction by Mitosis
Biology: Life on Earth (Audesirk)
Hydra: Asexual Reproduction by Mitosis
Chapter 11
Figure: 11.3c
Title:
Mitotic cell division in eukaryotes enables asexual reproduction
Caption:
Hydra, a freshwater relative of jellyfish, grows a miniature replica of itself (a bud) protruding from its side. When fully developed, the bud breaks off and assumes independent life.
Chapter 11

9. Genetically Identical Aspen Groves
Biology: Life on Earth (Audesirk)
Genetically Identical Aspen Groves
Chapter 11
Three separate aspen groves
Each produced asexually from single ancestor
Variable between groves
Identical within groves
Trees synchronously lost leaves
Trees synchronously turned yellow
Figure: 11.4
Title:
The trees in aspen groves are genetically identical
Caption:
Each tree grows up from the roots of a single ancestral tree. This photo shows three separate groves near Aspen, Colorado. In fall the behavior of their leaves shows the genetic identity within a grove and the genetic difference between groves. One entire grove is still green (bottom), the second has turned bright gold (middle), and the third has already lost its leaves (top).
Trees still green
Chapter 11

10. Mitosis, Meiosis, and the Sexual Cycle
Biology: Life on Earth (Audesirk)
Mitosis, Meiosis, and the Sexual Cycle
Chapter 11
Figure: 11.5
Title:
Mitotic and meiotic cell division in humans
Caption:
Mitotic cell divisions maintain and repair the bodies of adults. Within ovaries, meiotic cell division produces eggs; within testes, meiotic cell division produces sperm. Fusion of an egg and a sperm produce a fertilized egg that undergoes hundreds of mitotic cell divisions to produce a baby that can grow by additional mitotic cell divisions into an adult, completing the life cycle.
Chapter 11

11. Chromosome Condensation
Biology: Life on Earth (Audesirk)
Chromosome Condensation
Chapter 11
single-stranded chromosome
double helix uncondensed
double-stranded chromosome
double helices still uncondensed
DNA replication
Chromosome condensation
cell
1 double-stranded chromosome
2 double helices now condensed
base pairs
Figure: 11.6
Title:
Chromosome condensation
Caption:
Before cell division begins, the DNA double helix in each chromosome replicates. The two newly made double helices remain associated with each other. When cell division begins, the duplicate chromosomes condense and become visible. At this stage, each duplicated chromosome contains two identical DNA double helices. Each DNA double helix is contained within a sister chromatid. Condensation of the duplicated chromosome requires action of many proteins, including histones.
a chromatid
centromere 
closer look
still closer look
even closer look
Chapter 11

12. Human Chromosomes during Mitosis
Biology: Life on Earth (Audesirk)
Human Chromosomes during Mitosis
Chapter 11
Figure: 11.UN06a
Title:
Formation of sister chromatids
Caption:
Chapter 11

13. Biology: Life on Earth (Audesirk)
Human Karyotype, Male
Chapter 11
These are chromosomes from mitosis
Stained to show regions
Numbered by length
Occur in pairs
Figure: 11.UN06b
Title:
Formation of daughter chromosomes
Caption:
Chapter 11

14. The Eukaryotic Cell Cycle
Biology: Life on Earth (Audesirk)
The Eukaryotic Cell Cycle
Chapter 11
G0: nondividing
Mitosis
S: Synthesis of DNA; chromosomes duplicated
prophase
G1: Growth
anaphase
telophase
metaphase
cytokinesis
G2: Growth
interphase
cell division
Figure: 11.9
Title:
The eukaryotic cell cycle
Caption:
The eukaryotic cell cycle consists of two major phases, interphase and cell division. Each is divided into subphases.
Chapter 11

15. Biology: Life on Earth (Audesirk)
Phases of Mitosis, 1
Chapter 11
Interphase : The chromosomes (blue) are in the thin, extended state and appear as a mass in the center of the cell. The microtubules (red) extend outward from the nucleus to all parts of the cell.
Late prophase: Chromosomes (blue) have condensed and attached to microtubules of spindle fibers (red). Microtubules have reorganized to form the spindle; chromosomes, now condensed, are clearly visible.
Metaphase: The chromosomes have moved along the spindle microtubules to the equator of the cell.
Figure: 11.10
Title:
The cell cycle in a plant cell
Caption:
The eukaryotic cell cycle consists of two major phases, interphase and cell division. Each is divided into subphases.
Chapter 11

16. Separation of Sister Chromatids
Chapter 11
In metaphase, sister chromatids are held together at centromere
At end of metaphase, centromere releases sister chromatids
In anaphase, they move to opposite poles

17. Phases of Mitosis, 2 Chapter 11
Anaphase: Sister chromatids have separated, and one set of chromosomes moves along the spindle microtubule to each pole of the cell.
Telophase: The chromosomes have gathered into two clusters, one at the site of each future nucleus.
Next interphase: Chromosomes are relaxing again into their extended state. Spindle fibers are disappearing, and the microtubules of the 2 daughter cells rearrange into the interphase pattern.

18. Mitosis: Prophase - Metaphase
Biology: Life on Earth (Audesirk)
Mitosis: Prophase - Metaphase
Chapter 11
Duplicated chromosomes remain elongated
Chromosomes condense and shorten
Nucleolus disappears; Nuclear envelope breaks down
Late Interphase
Early Prophase
Late Prophase
Metaphase
Figure: 11.11a-d
Title:
The cell cycle in an animal cell
Caption:
(a) Late interphase: The chromosomes have been duplicated but remain elongated and relaxed within the nucleus. The centrioles have also been duplicated. (b) Early prophase: The chromosomes condense, shortening and thickening. The centrioles begin to move apart, and the spindle microtubules begin to form between them. (c) Late prophase: The nucleolus disappears; the nuclear envelope breaks down, and the spindle microtubules attach to the kinetochore of each sister chromatid (red spot). (d) Metaphase: Interactions between the kinetochores and the microtubules have lined up the chromosomes at the cell’s equator.
Centrioles have also been duplicated
Centrioles begin to move apart;
Spindle forms
Microtubules attach to kinetochores
Kinetochores align at cell’s equator
Chapter 11

19. Mitosis Anaphase - Cytokinesis
Biology: Life on Earth (Audesirk)
Mitosis Anaphase - Cytokinesis
Chapter 11
Free spindle fibers push poles apart
One set of chromosomes; Begin unwinding
Cytoplasm divided along equator
Figure: 11.11e-I
Title:
The cell cycle in an animal cell
Caption:
(e) Anaphase: Chromatids separate at the centromere, becoming independent chromosomes that move toward the opposite poles of the cell. The free spindle microtubules slide past one another, pushing the poles farther apart. (f) Telophase: One complete set of chromosomes reaches each pole. The chromosomes relax into their extended state, the spindle microtubules begin to disappear, and the nuclear envelopes begin to re-form. (g) Cytokinesis: At the end of telophase, the cytoplasm is divided along the equator of the parent cell, with each daughter cell receiving one nucleus and about half the original cytoplasm. (h) Interphase of daughter cells: The daughter cells enter interphase. The spindle microtubules disappear, the nuclear envelope re-forms, the chromosomes finish extending, and the nucleolus reappears.
Next Interphase
Anaphase
Telophase
Cytokinesis
Each daughter gets 1 nucleus & half of cytoplasm
Spindle disappears; Nucleolus reappears
Chromatids become independent chromosomes
Nuclear envelope re-forms
Chapter 11

20. Cytokinesis of a Ciliated Cell
Biology: Life on Earth (Audesirk)
Cytokinesis of a Ciliated Cell
Chapter 11
Daughter Cells
Figure: 11.12b
Title:
Cytokinesis in an animal cell
Caption:
Cytokinesis has almost separated the two daughter cells.
Cleavage Furrow
Chapter 11

21. Biology: Life on Earth (Audesirk)
Cytokinesis in Plants
Chapter 11
Vesicles fuse to form cell wall and membranes
Complete separation of daughter cells
Figure: 11.13
Title:
Cytokinesis in a plant cell
Caption:
Carbohydrate-filled vesicles produced by the Golgi complex congregate at the equator of the cell, forming the cell plate. The membranes of the vesicles will fuse to form the two plasma membranes separating the daughter cells; their carbohydrate contents form part of the cell wall.
Chapter 11

22. Biology: Life on Earth (Audesirk)
Meiosis I
Chapter 11
Homologous chromosomes exchange DNA & align on equator
Homologous chromosomes move to opposite poles
Homologous chromosomes pair and cross over
Figure: 11.14a-d
Title:
The details of meiotic cell division
Caption:
In meiotic cell division (meiosis and cytokinesis), the homologous chromosomes of a diploid cell are separated, producing four haploid daughter cells. Each daughter cell contains one member of each pair of parental homologous chromosomes. In these diagrams, two pairs of homologous chromosomes are shown, large and small. The yellow chromosomes are from one parent (for example, the father), and the violet chromosomes are from the other parent. (a) Prophase I. Duplicated chromosomes condense. Homologous chromosomes pair up and chiasmata occur as chromatids of homologues exchange parts. The nuclear envelope disintegrates, and spindle microtubules form. (b) Metaphase I. Paired homologous chromosomes line up along the equator of the cell. One homologue of each pair faces each pole of the cell and attaches to spindle microtubules via its kinetochore (red). (c) Anaphase I. Homologues separate, one member of each pair going to each pole of the cell. Sister chromatids do not separate. (d) Telophase I. Spindle microtubules disappear. Two clusters of chromosomes have formed, each containing one member of each pair of homologues. The daughter nuclei are therefore haploid. Cytokinesis commonly occurs at this stage. There is little or no interphase between meiosis I and meiosis II.
Prophase I
Metaphase I
Anaphase I
Telophase I
Chapter 11

23. Biology: Life on Earth (Audesirk)
Meiosis II
Chapter 11
Similar to Mitosis
Figure: 11.14e-I
Title:
The details of meiotic cell division
Caption:
In meiotic cell division (meiosis and cytokinesis), the homologous chromosomes of a diploid cell are separated, producing four haploid daughter cells. Each daughter cell contains one member of each pair of parental homologous chromosomes. In these diagrams, two pairs of homologous chromosomes are shown, large and small. The yellow chromosomes are from one parent (for example, the father), and the violet chromosomes are from the other parent. (e) Prophase II. If chromosomes have relaxed after telophase I, they recondense. Spindle microtubules re-form and attach to the sister chromatids. (f) Metaphase II. Chromosomes line up along the equator, with sister chromatids of each chromosome attached to spindle microtubules that lead to opposite poles. (g) Anaphase II. Chromatids separate into independent daughter chromosomes, one former chromatid moving toward each pole. (h) Telophase II. Chromosomes finish moving to opposite poles. Nuclear envelopes re-form, and the chromosomes become extended again (not shown here). (i) Four haploid cells. Cytokinesis results in four haploid cells, each containing one member of each pair of homologous chromosomes (shown here in condensed state).
Four Haploid Cells
Prophase II
Metaphase II
Anaphase II
Telophase II
Chapter 11

24. Biology: Life on Earth (Audesirk)
Chapter 11
Crossing Over
Homologues pair up
Protein strands zip together
Recombination enzymes snip and rejoin DNA
Homologs separate with new gene combinations
Figure: 11.15
Title:
The mechanism of crossing over
Caption:
1) Homologous chromosomes pair up side by side. 2) One end of each chromosome binds to the nuclear envelope. Protein strands “zip” homologous chromosomes together. 3) Homologous chromosomes are fully joined by protein strands. 4) Recombination enzymes bind to the chromosomes. Recombination enzymes snip chromatids apart and reattach the chromatids. Chiasmata are formed when one end of a chromatid of a paternal chromosome (yellow) is attached to the other end of a chromatid of a maternal chromosome (violet). 5) The protein strands and recombination enzymes leave as the chromosomes condense. The chiasmata remain as locations where homologous chromosomes are twisted around each other, helping to hold homologues together.
Chapter 11

25. Meiosis vs. Mitosis: Comparison of Spindles
Biology: Life on Earth (Audesirk)
Meiosis vs. Mitosis: Comparison of Spindles
Chapter 11
Meiosis: Duplicated chromosomes with one kinetochore; Paired homologues go to opposite poles.
Figure: 11.16
Title:
A comparison of the spindles formed during mitosis and meiosis I
Caption:
(a) In mitosis, homologous chromosomes are not paired. The kinetochores of sister chromatids are attached to kinetochore microtubules that lead to opposite poles. When the sister chromatids separate during anaphase, the newly independent daughter chromosomes move to opposite poles of the cell. (b) In meiosis I, homologous chromosomes are paired. Both kinetochores of the sister chromatids of a single chromosome are attached to kinetochore microtubules that lead to the same pole. During anaphase I, sister chromatids of each chromosome remain together, moving to the same pole, but homologous chromosomes separate and move to opposite poles.
Mitosis: Duplicated chromosomes with two kinetochores; Unpaired homologs split between sister chromatids, which go to opposite poles.
Chapter 11

26. Meiosis vs. Mitosis: Comparison of Stages
Biology: Life on Earth (Audesirk)
Meiosis vs. Mitosis: Comparison of Stages
Chapter 11
Figure: 1.1
Title:
A comparison of mitotic and meiotic cell divisions in animal cells
Caption:
In these diagrams, comparable phases are aligned. In both mitosis and meiosis, chromosomes are replicated during interphase. Meiosis I, with the pairing of homologous chromosomes, formation of chiasmata, exchange of chromosome parts, and separation of homologues to form haploid daughter nuclei, has no counterpart in mitosis. Meiosis II, however, is similar to mitosis.
Chapter 11

27. Metaphase Alignment Scenarios
Biology: Life on Earth (Audesirk)
Metaphase Alignment Scenarios
Chapter 11
Figure: 11.UN16
Title:
Shuffling of homologues in anaphase I and genetic variability
Caption:
Three pairs of homologous chromosomes will produce eight possible sets of chromosomes in anaphase I.
Chapter 11

28. Chapter 11
The end