D2.1.5

• A cell copies all of its DNA so that each daughter cell produced receives a full complement of genes, allowing it to perform any function required.
• Early interphase: a single chromatid before DNA replication
• Prophase: chromosome with two chromatids held together by cohesin loops
• Metaphase: microtubules attached to centromeres pull on chromatids but cohesin loops hold them together
• Anaphase: cohesin loops have been cut, so sister chromatids can separate and be pulled to opposite poles
• Uncondensed DNA cannot be seen because it is too narrow. It gradually becomes shorter and fatter during the early stages of mitosis and meiosis and are then visible.
• One chromosome consists of two strands which are called chromatids.
• Sister chromatids are genetically identical.