The video explains how feedback controls in the cell cycle prevent mitosis before DNA replication is complete. It describes the normal cell cycle, where DNA replicates during the S phase, leading to mitosis. Caffeine disrupts this control, allowing mitosis to occur prematurely. Hydroxyurea blocks DNA synthesis, inhibiting replication and division. When both caffeine and hydroxyurea are present, the control mechanism fails, causing the nucleus to divide without complete DNA replication, resulting in incomplete genomes.

What is the primary role of feedback controls in the cell cycle?

• To inhibit mitosis

• To prevent nuclei from dividing before all steps are completed

• To ensure nuclei divide before DNA replication

• To speed up the cell cycle

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NGSS.HS-LS1-4

During which phase does DNA replication occur in the cell cycle?

• G1 phase

• S phase

• M phase

• G2 phase

How does caffeine affect the feedback control mechanism in the cell cycle?

• It blocks DNA synthesis

• It inactivates the feedback control mechanism

• It prevents mitosis

• It speeds up DNA replication

What is the role of hydroxyurea in the cell cycle?

• It accelerates mitosis

• It blocks the synthesis of DNA building blocks

• It promotes DNA replication

• It inactivates feedback controls

Tags

NGSS.HS-LS1-4

What happens to the cell cycle when both caffeine and hydroxyurea are present?

• DNA replication occurs but mitosis is inhibited

• The nucleus divides without DNA replication

• The cell cycle proceeds normally

• The cell cycle stops completely

Tags

NGSS.HS-LS1-4

What is the consequence of nuclear division without DNA replication?

• Increased DNA synthesis

• Faster cell division

• Cells with incomplete genomes

• Cells with complete genomes