In animal cells, typically which organelle is only provided by the sperm to the oocyte following fertilization?

Correct option is D

During fertilization, the sperm contributes minimal cytoplasmic components to the oocyte. The primary contribution of the sperm is its nucleus (carrying paternal DNA) and a pair of centrioles, which play a crucial role in organizing the mitotic spindle for the first embryonic divisions.

• The oocyte provides most of the cytoplasmic organelles, including mitochondria, peroxisomes, and nucleoli.
• The sperm's mitochondria are actively degraded after fertilization, ensuring maternal inheritance of mitochondria.
• Centrioles from the sperm are essential for assembling the centrosome in the zygote, which is required for subsequent cell divisions.

1. Option (1) Nucleolus: The nucleolus is formed post-fertilization from maternal components and does not come from sperm.
2. Option (2) Peroxisomes: Peroxisomes are inherited maternally, as they are part of the egg’s cytoplasm.
3. Option (3) Mitochondria: Mitochondria in the zygote are maternal due to selective degradation of paternal mitochondria.
4. Option (4) Centrioles: The sperm contributes centrioles, which are essential for centrosome formation and early cell division.

Information Booster

1. Role of Centrioles:

   • Centrioles help form the mitotic spindle, ensuring proper chromosomal segregation during early embryonic development.

2. Maternal Inheritance of Mitochondria:

   • In most animals, zygotic mitochondria are exclusively maternal due to the degradation of paternal mitochondria after fertilization.

3. Sperm’s Contribution to the Zygote:

   • Provides haploid DNA and centrioles.
   • The midpiece (containing mitochondria) and tail are left outside or degraded.

4. Centrosome Formation in the Zygote:

   • The centrosome is assembled from paternal centrioles and maternal pericentriolar material.

5. Why Doesn't the Oocyte Provide Centrioles?

   • Oocytes lack centrioles because they are degraded during oogenesis. This ensures that only paternal centrioles contribute to the zygote’s centrosome.

6. Implications in Fertility:

   • Defects in sperm centrioles can lead to failed fertilization or abnormal embryonic development.

7. Species Variation:

   • While in most mammals, sperm-derived centrioles are essential, some species (e.g., rodents) can form centrioles de novo without sperm contribution.