Freshly released human egg has
A. Two X-chromosome
B. One Y-chromosome
C. One Y-chromosome & one X-chromosome
D. One X-chromosome
Correct Answer: D. One X-chromosome
Explanation
A freshly released human egg (ovum) has a haploid number of chromosomes.
Explanation
- During oogenesis, the egg undergoes meiosis, reducing the chromosome number from diploid (46 chromosomes) to haploid (23 chromosomes).
- At ovulation, the egg is released from the ovary as a secondary oocyte, which has:
- 23 chromosomes (haploid, n)
- Arrested in metaphase II of meiosis until fertilization
Final Answer
A freshly released human egg has 23 chromosomes (haploid number).
Other Options Details
Here is the description of all options:
A. Two X-chromosome
- This means the cell contains two X sex chromosomes (XX).
- This combination is normally found in female individuals.
- Example: A normal human female somatic cell has 46 chromosomes, including XX as the sex chromosomes.
B. One Y-chromosome
- This means the cell contains only a single Y chromosome.
- A cell with only a Y chromosome cannot exist normally on its own, because a Y chromosome must pair with at least one X chromosome.
- The Y chromosome determines male sex characteristics.
C. One Y-chromosome & One X-chromosome
- This combination is XY, which is the normal sex chromosome pair in males.
- A normal human male somatic cell has 46 chromosomes, including XY as the sex chromosomes.
- The presence of the Y chromosome is what leads to male development.
D. One X-chromosome
- This means the cell has only one X chromosome, with no second sex chromosome.
- In humans, this condition is seen in Turner syndrome (XO), where the individual is genetically female but has only 45 chromosomes instead of 46.
- Can lead to developmental differences and infertility.
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Writer: Vandita Singh, Lucknow (GS India Nursing Group