Question

In which egg is the yolk found in the centre and the peripheral part is yolk-less?

• A. Homolecithal
• B. Microlecithal
• C. Centrolecithal
• D. Telolecithal

Answer 1

The correct option is C Centrolecithal

Many animal eggs contain yolk, a mixture of proteins, phospholipids, and fats that serves as food for the developing embryo. The amount and distribution of yolk vary among different animal groups, depending on the needs of the embryo.

Mammalian eggs have very little yolk, because the embryo obtains maternal nutritional support throughout most of its development; whereas the eggs of birds and reptiles must contain sufficient yolk to sustain the embryo until hatching.

Echinoderm eggs typically need only enough yolk to nourish the embryo until it becomes a tiny larva capable of obtaining its own food.

Most invertebrates and simple chordates have isolecithal eggs with relatively small amounts of yolk uniformly distributed through the cytoplasm.

Many vertebrate eggs are telolecithal, meaning they have large amounts of yolk concentrated at one end of the cell, known as the vegetal pole. The opposite, more metabolically active, pole is the animal pole.

The eggs of amphibians are moderately telolecithal (mesolecithal).

Centrolecithal describes the placement of the yolk in the centre of the cytoplasm of ovums. Many arthropod eggs are centrolecithal.