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Lecture 4: Replication of Eukaryotic cells

Cells are derived from other cells. Cell replication or cell division mechanism varies among the organism’s cell and type of cells.

Whats so important about cell replication?

Over time, cells die and thus cell replication must be necessary in order to produce more cells so your body would not fall part!

Remember, the Cell Theory

  1. Cell is the basic unit of life
  2. Cells come from other cells
  3. Cells make up living things

Thus, without replication of cells, we would be extinct

What types of cell replication occurs in eukaryotic cells?

In eukaryotic cells, mitosis and meiosis are cell division mechanisms seen in somatic cell and sex cells, respectively. Sex cells are gamete cells such as sperm and egg. Somatic cells are all other cells that are not sex cells. Other types of eukaryotic cell replication includes: schizogony, budding, and spore formation.

Photo from Nobelprize.org

MITOSIS

The cell cycle as seen here is in Mitosis:

G1 = growth of cell size

S = synthesis stage (chromosomes and replication of DNA)

G2= prep for mitosis

Cyclin, is a protein that is used to control the cell cycle.

Photo from Wikipedia

In Mitosis, diploid cells are replicated into two 2n daughter cells. This basically means the daughter cells or replicated cells contain the same pair of chromosomes as the original cell that was being replicated.

  1. Interphase– cell is growing larger and getting ready for cell replication
  2. Prophase – condensation of chromosomes
  3. Metaphase – spindle fibers, centromere, centrioles are developed at the polar ends of the cell, and where the chromosomes line up at the middle of the cell
  4. anaphase – spindle fibers grabs the centromeres of the chromatids and pulls the chromosome pairs in half to the polar ends
  5. Telophase – the stage in which the cell begins to pinch off at the middle
  6. Cytokineses – the final separation of the cell, resulting 2 daughter cells of the same copies of the paired chromosomes (2n or diploid daughter cells)

MEIOSIS

Unlike mitosis, it has two stages, which can be seen on pg. 346 of the textbook.

Meiosis I follows the same pattern as that of Mitosis. After cytokineses in Meiosis I is Meosis II where DNA replication is no longer necessary.

MEIOSIS II

  • Prophase II – presence of spindle fibers
  • Metaphase II – alignment of the 2n chromosomes at the middle
  • Anaphase II – separation of the sister chromatids away into the polar sides
  • Telophase – pinching of the cell
  • Cytokineses – closing of the pinching to make 4 haploid nuclei (1n) cells

In mitosis and meiosis we see that one is asexual and the other is sexual reproduction, respectively.

BINARY FISSION – an asexual reproduction in which the cell replicates its own chromosome.

  1. The DNA duplicates and is attached to the plasma membrane.
  2. The cell elongates as the septum is developed between the replicated chromosomes at the midline.
  3. Upon completion, the duaghter cells remain attach to each other, some completely separate.
  4. The process repeats itself. (i.e. Escherichia coli)

SCHIZOGONY (p. 347)

  • Multiple mitosis is occurring within the cell without cytokineses.
  • The result is a schizont which is a cell with multinucleates.
  • Cytokineses follows releasing uninucleates merozoites.

Example: Malaria caused by protozoan, Plasmodium faciparum

BUDDING & SPORE FORMATION (seen in Yeast)

  • an outgrowth of the cell is seen with a copy of the genetic material from the parent becomes enlarged
  • bud is cut off from parent cell while it is small

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The former contents were notes taken from Professor Phil Hawkins at Foothill College Bio 41 in Winter 2010. Additional information are also taken from the textbook: Microbiology with Diseases by Taxonomy, 2nd edition, by Robert Bauman.

One Response to “Lecture 4: Replication of Eukaryotic cells”

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  1. dor

    Nice lecture

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