Cellular Reproduction - Mitosis
MITOSIS = Cell division When parent cell forms two identical daughter cells Momma! Daughters!
Why do cells divide? Multicellular organisms: 1) Growth 2) Maintenance/repair of tissues (ex: blood cells) Unicellular organisms: Asexual reproduction
Replication of DNA – copying the genetic material Distribution of DNA – dividing the genetic material evenly between two cells Cytokinesis – dividing the cytoplasm between two cells Cell division involves:
DNA double helix proteins Chromatin Chromosome DNA is a double helix When stretched out, it can be as long as 2 meters Normally, DNA in the nucleus is called CHROMATIN. It is seen as a thin thread loosely wrapped around proteins like a beaded necklace. Just before cell division, DNA coils tightly into a chromosome. The chromosome is very compact and can be seen with a light microscope
Replication: Copying the DNA Occurs before the DNA condenses ( S phase of interphase ) The original and its identical copy are called sister chromatids. Sister chromatids are attached to each other by a centromere.
During mitosis, the sister chromatids will be separated so each cell has the complete DNA information
A chromosome is made up of two identical halves called chromatids.
The Cell Cycle Time from the formation of a cell until it divides
The Cell Cycle Two major phases: Interphase Most cell activities occur Growth Making proteins Performing specialized functions
The Cell Cycle Two major phases: Mitosis Cell division Cycle time varies: Embryonic cells complete the cycle in hours Stem cells are in interphase for 20 hours Nerve cells remain in interphase
G1 phase of interphase – growth, duplication of organelles, making proteins.
S-phase of interphase: DNA replication G2 phase: duplication of centrosome
Stages of Mitosis
Prophase : centrosomes separate and spindle forms; chromosomes are condensing
ProMetaphase : break down of nuclear envelope; centrosomes arrive at two opposite poles; spindles attach to chromosomes
Metaphase : chromosomes move to the equator
Anaphase : sister chromatids separate (become daughter chromosomes)
Telophase : spindle disappears; nuclear envelope forms, DNA unfolds cytokinesis: cytoplasm divides
Two daughter cells are now complete
Cytokinesis Division of the Cytoplasm Animal cells: cleavage furrow forms Cell pinches in towards the center
Cytokinesis Plant cells: cell plate forms New cell walls and membranes form from the cell plate
SUMMARY: What happens to chromosomes prior/during mitosis? 1) chromosomes replicate 2) chromosomes coil 3) chromosomes align 4) sister chromatids separate 5) chromosomes uncoil **interphase **prophase **metaphase **anaphase **telophase
Animal Prophase Plant
Animal Metaphase
Animal Anaphase
Animal Telophase
Cancer results from uncontrolled cell division. A cancerous growth is called a tumor. The Cell Cycle and Cancer
In Cancer, often one of the checkpoints that regulate mitosis don’t work
Cancer cells Lack differentiation Have abnormal nuclei Undergo metastasis The Cell Cycle and Cancer
Cancer treatment: Radiotherapy Chemotherapy Hormonal therapy
Consumption of foods rich in vitamins A and C (dark green leafy vegetables, carrots, fruits) Avoid salted, pickled or smoked food. Consumption of vegetables from the cabbage family. Cancer prevention:
1. Cellular reproduction is an important process for growth and development as well as repair of tissues in multicellular organisms. 2.The cell cycle is composed of a number of phases where specific events occur (interphase and mitosis are the two major phases). 3. Mitosis is divided into four phases: prophase, metaphase, anaphase and telophase, which is followed by cytokinesis 4. Cancer is caused by uncontrolled cell division Learning objectives