Tim Hunt's Lab Experiment on Sea Urchin Eggs
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Tim Hunt's Lab Experiment on Sea Urchin Eggs

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Questions and Answers

What was the key observation in Tim Hunt's experiment with sea urchin eggs?

  • A protein whose levels fluctuated in a cyclic manner as the cells progressed through the cell cycle (correct)
  • A protein that increased steadily without any fluctuations
  • A protein that remained constant throughout the cell cycle
  • A protein that was present only during mitosis

    • How were the cycling proteins identified in the experiment?

  • By adding radioactive methionine to the fertilized sea urchin eggs and analyzing protein samples at regular intervals (correct)
  • By directly observing the cells under a microscope
  • By measuring the levels of cyclin mRNA
  • By using a specific antibody to detect the cycling proteins

    • What was the characteristic pattern observed for the cycling proteins?

  • Their levels gradually increased and remained high throughout the cell cycle
  • Their levels gradually built up but were rapidly degraded during cell division (correct)
  • Their levels remained constant throughout the cell cycle
  • Their levels gradually decreased and remained low throughout the cell cycle

    • What was the correlation observed between the cycling proteins and cell division?

    <p>The levels of the cycling proteins fell just before cleavage or cell division</p> Signup and view all the answers

    Why were these cycling proteins named 'cyclins'?

    <p>Because their levels cycled or fluctuated during the cell cycle</p> Signup and view all the answers

    In which other organisms were similar cycling proteins observed?

    <p>Clams and sea urchins from different species</p> Signup and view all the answers

    What was the correlation observed between the peak of cyclin levels and MPF activity?

    <p>The peak of cyclin levels correlated with higher MPF activity</p> Signup and view all the answers

    What was the biochemical composition of MPF?

    <p>It had two subunits</p> Signup and view all the answers

    What was the significance of the observation that cyclin levels fluctuated during the cell cycle?

    <p>It suggested that cyclins might play a role in regulating the cell cycle</p> Signup and view all the answers

    What was the significance of the correlation between cyclin levels and MPF activity?

    <p>It suggested that cyclins might be involved in the regulation of MPF activity</p> Signup and view all the answers

    Study Notes

    Tim Hunt's Experiment with Sea Urchin Eggs

    • The key observation in Tim Hunt's experiment was the discovery of proteins that oscillated in concentration throughout the cell cycle, peaking at mitosis and decreasing after cell division.

    Identification of Cycling Proteins

    • The cycling proteins were identified through the use of radioactively labeled amino acids to label newly synthesized proteins in sea urchin eggs.
    • The labeled proteins were then separated using gel electrophoresis, and the cycling proteins were identified as those that oscillated in concentration throughout the cell cycle.

    Characteristics of Cycling Proteins

    • The characteristic pattern observed for the cycling proteins was a rapid increase in concentration during interphase, peaking at mitosis, and then rapid degradation after cell division.
    • This oscillation pattern was observed to be repeated in every cell cycle.

    Correlation between Cycling Proteins and Cell Division

    • The correlation observed between the cycling proteins and cell division was that the peak of cycling protein levels coincided with the onset of mitosis.
    • This suggested a role for these proteins in regulating the cell cycle.

    Origin of the Term "Cyclins"

    • The cycling proteins were named "cyclins" due to their cyclical pattern of concentration throughout the cell cycle.

    Conservation of Cyclins across Organisms

    • Similar cycling proteins were observed in other organisms, including clam and frog eggs, as well as in mammalian cells.
    • This suggested that the mechanism of cell cycle regulation is highly conserved across species.

    Correlation between Cyclin Levels and MPF Activity

    • The peak of cyclin levels was observed to coincide with the peak of Maturation Promoting Factor (MPF) activity.
    • This suggested a role for cyclins in activating MPF, which in turn regulates the cell cycle.

    Biochemical Composition of MPF

    • MPF is a complex of cyclin-dependent kinase (CDK) and cyclin.

    Significance of Cyclin Level Fluctuations

    • The significance of the observation that cyclin levels fluctuate during the cell cycle is that it suggests a mechanism for regulating the cell cycle.
    • This observation implied that the cell cycle is regulated by a cyclical pattern of protein synthesis and degradation.

    Significance of Correlation between Cyclin Levels and MPF Activity

    • The significance of the correlation between cyclin levels and MPF activity is that it suggests a molecular mechanism for regulating the cell cycle.
    • This correlation implied that the oscillation of cyclin levels is essential for the proper progression of the cell cycle.

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    Description

    Learn about an experiment conducted in Tim Hunt's lab involving sea urchin eggs to study cell cycle regulators by observing the fluctuation of specific proteins throughout the cell cycle. Radioactive methionine was used to track protein synthesis in fertilized sea urchin eggs at intervals of 10 minutes.

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