Before You Begin
Question #45256
The Question
An oogonium in the phase of a human female has 46 chromosomes and a DNA content of 2C. Which of the following correctly identifies the chromosome number and DNA content of a newly ovulated secondary oocyte, and the specific physiological event required to reduce its DNA content to 1C?
Options
- A.
23 chromosomes, 1C DNA; The LH surge prior to ovulation triggers the completion of Meiosis I.
- B.
23 chromosomes, 2C DNA; The entry of a sperm into the oocyte cytoplasm triggers the completion of Meiosis II.
- C.
23 chromosomes, 2C DNA; The fusion of male and female pronuclei (syngamy) during fertilization.
- D.
46 chromosomes, 2C DNA; The breakdown of the Metaphase II arrest by the Anaphase Promoting Complex.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Meiotic Arrest Points|Secondary Oocyte|Chromosomal Segregation
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: Students frequently confuse ploidy (chromosome number, n) with DNA content (C).
A common misconception is assuming that because Meiosis I creates a haploid (n) cell, the DNA content must also be fully reduced to 1C.
This question tests the understanding that a secondary oocyte's chromosomes still possess two sister chromatids (2C), and that sperm entry (not syngamy) is the mechanical trigger for Anaphase II, which finally reduces the DNA content to 1C.
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Cell Cycle and Cell Division - Class 11 |
| Concept | DNA vs Chromosome Content |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |