week of 1/26/09

this week we learned a lot about the process of mitosis-which is just a fancy word for cell reproduction.

the steps of mitosis:

Interphase (well kind of.  some people count it as the first step of mitosis, but we are not.  but it still takes part in cell reproduction)-when the chromosomes are copied; chromosomes appear as threadlike coils (chromatin) at the start, but each chromosome and its copy (sister chromosomes) change to sister chromatids at the end of this phase

Prophase-mitosis begins (cell begins to divide); centrioles (or poles) appear and begin to move to opposite ends of cell; spindle fibers form between the poles

Metaphase-chromatids (or pairs of chromosomes) attach to the spindle fibers

Anaphase-chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell

Telophase-two new nuclei form; chromosomes appear as chromatin (threads rather that rods); mitosis ends

Cytokinesis (once again, some don't count this as a step of mitosis.  we are not.  but it is part of reproduction)-cell membrane moves inward to create two daughter cells-each with its own nucleus with identical chromosomes

Mitosis terms and explanations:

• 2 chromatids make up a chromosome
• 2 chromatids are connected by a centromere
• unraveled DNA is called chromatin
• spindle fibers attach to the chromatids
• when cell reproduction is not occurring one chromatid is just called a chromosome
• during cell reproduction, 2 chromatids are called a chromosome
• a centrosome splits into 2 centrioles
• during reproduction, the centrosome splits into two centrioles that go to opposite sides of the cell and produce spindle fibers
• spindle fibers pull apart 2 sister chromatids-the chromatids reach towards each other which is why they look like V's (this happens during anaphase)
• during metaphase, the spindle fibers attach to the centromere and line up the chromatids in the center of the cell then pull them apart
• during telophase, the cells are remaking the nucleus and organelles so that during cytokinesis the cell can split into 2 daughter cells

this week was full of great information.  its a little confusing, but very interesting.  until next week!

~*Mary*~