Final answer:
Cohesin proteins bind to chromosomes during prophase and maintain the connection between sister chromatids until they separate in anaphase. During metaphase, sister chromatids aligned at the metaphase plate are held by cohesin, ensuring proper segregation during cell division.option 2 is correct answer.
Step-by-step explanation:
When Does Cohesin Bind to Chromosomes?
The protein cohesin is integral to cell division, particularly during the stages of mitosis. Cohesin binds to chromosomes during prophase of mitosis, ensuring that the sister chromatids remain connected until they are ready to separate. As the cell cycle progresses, during metaphase, all chromosomes align at the metaphase plate with their sister chromatids still firmly joined by these cohesin proteins.
This attachment is maintained until the onset of anaphase, the stage in mitosis where the cohesin proteins finally degrade, allowing the sister chromatids to part and be pulled to opposite poles of the dividing cell. It is at this stage that visible cell elongation occurs, and the cell prepares for eventual division into two separate entities during the telophase and subsequent cytokinesis.
The engagement of cohesin proteins is also significant during meiosis; specifically during prophase I, where they help in aligning homologous chromosomes together, a process which is crucial for the genetic diversity resulting from sexual reproduction.