EXAM 4 NOTEs - EXAM 4 Videos Cell Cycle Mitosis Ploidy...

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EXAM 4 Videos: Cell Cycle Mitosis Ploidy Meiosis Genetic Definitions I Genetic Formations I Monohybrid Cross Di-hybrid Cross Gamete Formation II Gamete Formation III Genetic Variation Cell Signaling Cell Signaling Regulation Cell Cycle: The life of a cell: All cells come from preexisting cells
Cytokinesis – starting point of cell cycle; end of cell division; end of one cell’s life and beginning of another’s o At the end of cytokinesis and beginning of G1, chromosomes are un-replicated o Stay this way all the way through G1 G1 – Gap 1 o First stage after cytokinesis that a cell is in is known as G1 o G = GAP o chromosomes always un-replicated S – Synthesis o Start with unreplicated chromosomes o All DNA will be replicated during S so at the end of S, all chromosomes will be replicated chromosomes o Stay this way all the way through G2 o During S phase is when we have replication o DNA in the cell is going to replicate during S phase o synthesis of DNA (replication) o not called synthesis, called replication o all DNA is replicated and 2 molecules of DNA made will be held together G2 – Gap 2 o second gap phase o chromosomes are held together
o amount of chromosomes is unchanged and amount of DNA is doubled Cell Division o Ends with the division of the cytoplasm (cytokinesis) o Then we go back into G! o cell division (mitosis or meiosis) o Go from replicated chromosomes to unreplicated chromosomes Interphase - From the beginning of G1 all the way to G2 Then after interphase, I have some form of cell division Always begin division coming out of G2 [Figure 12.5] Start at beginning of G1 Then I’m in interphase Then I go to S where my DNA is synthesized, really a process known as replication I then go to G2 And then I have a cell division, in this case mitosis but it can also be meiosis Chromosome Structure: Eukaryotes: Chromosomes are composed of DNA and histone proteins that DNA is wrapped on
During interphase, that DNA is relaxed or extended During cell division, that DNA is condensed or supercoiled, it is all coiled up in a dense or tight structure Chromosomes that we think of are really chromosomes as they exist during cell division, in their condensed or supercoiled state Can be un-replicated and consist of one molecule of DNA Can be a replicated molecule and consist of 2 identical molecules of DNA, held together Still only one chromosome, except one has twice as much DNA as the other [Figure 12.4 and 12.5] Have an unreplicated chromosome DNA replicates during the S phase of the cell cycle I now have a replicated chromosomes composed of two sister chromatids which are identical Then those separate and I have two separate unreplicated chromosomes Amount of Chromosomes I have: I have one chromosome in Stage 1 of the figure
I have one chromosome in Stage 2 of the figure I have two chromosomes in Stage 3 of the figure, one in each cell Amount of DNA that I have: I have one molecule of DNA in Stage 1 of the figure

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