HISTOLOGY-Lecture 2-Cell Cycle/Cell Division

• Interphase
• -G1 - Gap 1 phase
• -S - synthesis phase
• -G2 - Gap 2 phase

Mitosis - cell division

G0 - outsied phase

• G1- gap phase
• -synthesis of
• RNA
• regulatory proteins for DNA replication
• enzymes for synthetic activities
• -reestablish nucleoli
• -duplication of centrioles begun
• -nucleoli reappear
• -growth of cell occurs

• S- synthesis phase
• -duplication of genome (replication)
• twice the amount of DNA now available
• - nucleoproteins imported & incorporated
• -duplication of centrioles completed

• G2 -gap 2 phase
• -synthesis of
• RNA needed for cell division
• proteins needed for cell division
• tubulin needed for microtubule production
• DNA analyzed for errors & corrected
• -storage of energy needed for cell division

• cell in permanent G1 phase
• cell cannot divide

• ex:
• -neurons
• -muscles cells

• -synthesis of
• RNA
• regulatory proteins for DNA replication
• enzymes for synthetic activities

• -reestablish nucleoli
• -duplication of centrioles begun
• -nucleoli reappear
• -growth of cell occurs

phase of interphase

• -duplication of genome (replication)
• twice the amount of DNA now available

• - nucleoproteins imported & incorporated
• -duplication of centrioles completed

phase of interphase

• -synthesis of
• RNA needed for cell division
• proteins needed for cell division
• tubulin needed for microtubule production
• DNA analyzed for errors & corrected

-storage of energy needed for cell division

phase of interphase

division of the nucleus that results in the daughter cells having the same number of chromosomes as the parent cell

• -daughter cells have the same # of chromosomes as the parent cell
• -2 daughter cells are produced
• -found in somatic cells

• Karyokinesis (division of the nucleus)
• -Prophase
• -Metaphase
• -Anaphase
• -Telophase

Cytokinesis (division of the cytoplasm)

division of the nucleus during Mitosis

• steps:
• -Prophase
• -Metaphase
• -Anaphase
• -Telophase

• 1. chromatin -> chromosomes
• - chromatids-half chromosome
• -centromere-constricted part of chromosome
• -kinetochore - microtubule organizing center (MTOC) developes from here

2. Nucleoli disappear

• 3.Centrosome divides
• -one centriole
• -one MTOC

4. one centriole + one MTOC migrates

• 5.spindle apparatus forms from MTOC
• -astral rays
• -spindle fibers

*Prometaphase begins

1. nuclear membrane disappears

• 2. spindle fibers
• - reach chromosomes
• -polar microtubules attach to microtubules from other side
• -kinetochore microtubules attach to kinetochore

1. chromosomes maximally condensed

2.spindles attached to kinetochore

3. chormosomes line up at equator

1. sister chromatids pull appart to opposite poles

2. cytokinesis begins

1. nuclear membrane reappears

2. chromosomes -> chromatin

3. nucleoli reappear (NOR function) - G1

4.spindle apparatus disappears

division of cytoplasm

begins during anaphase

actin & myosin involved

cell division that results in the daughter cells having 1/2 the number of chromosomes as the parent cell

-two divisions

-daughter cells have 1/2 the chromosomes of the parent cell

-4 daughter cells are produced

-gamete production

• Reductional Division
• 1. Prophase 1
• 2. Metaphase 1
• 3. Anaphase 1
• 4. Telophase 1
• 5. Interphase

• Equatorial Division
• 1. Prophase 2
• 2. Metaphase 2
• 3. Anaphase 2
• 4. Telophase 2

1. Prophase 1

2. Metaphase 1

3. Anaphase 1

4. Telophase 1

5. Interphase

1. Prophase 2

2. Metaphase 2

3. Anaphase 2

4. Telophase 2

• nuclear membrane breaks down
• chromatin ->chromosomes
• nucleoli disappear
• centriole migrates
• spindle apparatus forms
• homologus cheomosomes synapse
• crossing over takes place

• leptotene
• zygotene
• pachytene
• diplotene
• diakinesis

subdivision of Prophase 1 of Meiosis

chromatin condensation begins

subdivision of Prophase 1 of Meiosis

• chromosome condensation
• chromosomes become visible
• homologous chromosomes synapse

subdivision of Prophase 1 of Meiosis

• chromosome condensation
• crossing over occurs

subdivision of Prophase 1 of Meiosis

• chromosome condensation
• chiasmata appear
• (-crossing over points become visible)

subdivision of Prophase 1 of Meiosis

• max condensation
• nucleoli disappear
• nuclear membrane disappears
• centriole migrates
• spindle apparatus forms

• homologous chromosomes line up
• spindle fibers attach to kinetochore

homologous chromosomes separate

• nuclear membrane reforms
• chromosomes -> chromatin
• nucleoli reforms
• spindle apparatus disappears
• cytokinesis occurs

• short
• no S phase

* very mitotic

• 1. Prophase 2
• 2. Metaphase 2
• 3. Anaphase 2
• 4. Telophase 2

• nuclear membrane disappears
• chromatin -> chromosomes
• nucleoli disappear
• one centriole migrates
• spindle apparatus forms

• chromosomes line up in the middle
• spindle fibers attach

chromatids separate

• nuclear membrane reforms
• chromsomes -> chromatin
• nucleoli reforms
• spindle apparatus disappears
• cytokinesis