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Many students preparing for the DAT struggle with telling apart chromosomes, chromatids, and sister chromatids. This topic appears frequently in the Biology section, and confusion often leads to missed questions. Here is a clean, high-yield breakdown designed for fast review.
Chromosome vs. Chromatid — The Key Difference
A chromosome is defined by the number of centromeres.- Before S phase: 46 chromosomes, 46 chromatids
- After S phase: 46 chromosomes, 92 chromatids
- After Meiosis I: 23 chromosomes, 46 chromatids (haploid)
- After Meiosis II: 23 chromosomes, 23 chromatids
Quick Reference Table (2n = 46)
| Stage | Chromosomes | Chromatids | Ploidy |
|---|---|---|---|
| G1 | 46 | 46 | Diploid |
| S Phase | 46 | 92 | Diploid |
| G2 | 46 | 92 | Diploid |
| After Meiosis I | 23 | 46 | Haploid |
| After Meiosis II | 23 | 23 | Haploid |
Practice Question
A human cell (2n = 46) has just completed S phase. How many chromosomes and chromatids are present?a. 23 chromosomes and 46 chromatids
b. 46 chromosomes and 46 chromatids
c. 46 chromosomes and 92 chromatids
d. 92 chromosomes and 92 chromatids
e. 92 chromosomes and 46 chromatids
Correct Answer: c
After S phase, each chromosome consists of two sister chromatids. Chromosome number is based on centromeres, so the cell has 46 chromosomes and 92 chromatids.
Full Blog Version
For the full explanation with diagrams and examples:Chromosome vs. Chromatid: The Simplest DAT Explanation for Students
https://orgoman.com/blogs/dental-admissions-test-and-road-to-dental-school-acceptance/chromosome-vs-chromatid-the-simplest-dat-explanation-for-students
Additional DAT Resources
DAT Destroyer🦷 DAT Destroyer 2025 – The Proven Study System for the Dental Admission Test
Dynamite Biology Review
Dr. Jim Romano Biology Review – In-Depth DAT/OAT Concept Guide (Spiral-Bound)
DAT & OAT Classes (Online and In-Person)
2026 Winter DAT and OAT Classes with Dr. Jim Romano | In Person or Online
Free Biology Review (Download in the DAT Destroyer Study Group on Facebook)
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