Class Summary - Today we reviewed what DNA looked like by examining the DNA models that we put together yesterday. Then we started discussing the cell cycle. The cell cycle comes in 2 parts; interphase and mitotic phase. Today we focused on interphase. Interphase has three stages where the cell prepares to divide. Depending on the cell, interphase could be very short or very long. The first stage of interphase is the G1 phase. We remember what happens this way by thinking 'growth' phase. Not really growth of the cell in size but doubling of organelles and creating proteins that need to be made for cell division. The next phase is the S phase. We remember this phase by thinking 'synthesis'. This is when DNA replication takes place. In order to have two identical cells, we need two identical pieces of DNA. In order to make them identical we need to use the original DNA strand as a template. Helicase unwinds and unzips the halves of DNA. Polymerase brings free floating nucleotides in the nucleus to the unzipped strand where complementary pairs bond together with a hydrogen bond. The result is two exact copies of DNA; one for each daughter cell. We showed this process on our models. The final phase of interphase is the G2 phase. This we remembered as 'finalize'. During this phase proteins are finished up to make division possible (like microtubules). There will be a 5 question quiz tomorrow (2 phases of the cell cycle; interphase and mitosis and the three phases of interphase with their signal words).
Homework - Study for 5 Question Quiz on Cell Cycle Tomorrow
Class Objectives - Students will explain the interphase portion of the cell cycle, Students will use models to represent DNA replication.
DNA Replication in the S Phase of Interphase
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