OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

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Get ready for the OCR GCSE Biology exam with our comprehensive quiz, featuring flashcards and multiple choice questions. Understand the exam format, key topics, and effective study strategies to excel.

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What is the first stage of mitosis characterized by?

Condensed chromosomes align at the center of the cell
Two DNA copies spread out in long strings
The nuclear membrane disintegrates
Chromosomes form X-shaped structures

The correct answer is: Two DNA copies spread out in long strings

The correct choice describes a crucial feature of prophase, the first stage of mitosis. During prophase, chromatin condenses to form distinct chromosomes, making them visible under a microscope. Each chromosome consists of two identical sister chromatids joined at a region called the centromere. This condensation is significant because it prepares the chromosomes for the orderly separation that takes place during later stages of mitosis. In this stage, the nuclear envelope begins to break down, allowing the spindle fibers to interact with the chromosomes. Understanding the structure of chromosomes during this stage highlights the importance of chromosomal organization and maintenance of genetic information as the cell prepares to divide.