What type of twins are formed from a single fertilized ovum that later splits into two halves?

• A. Dizygotic
• B. Monozygotic
• C. Fraternal
• D. Identical

Answer: (B)

The correct answer is based on the definition of monozygotic twins, which are indeed formed from a single fertilized ovum. When this ovum, or zygote, undergoes cleavage and eventually splits into two separate embryos, each embryo develops into a genetically identical individual. This is a unique characteristic of monozygotic twins, which distinguishes them from dizygotic twins and other types.

Dizygotic twins, also known as fraternal twins, arise from two separate fertilized ova, leading to siblings that share about 50% of their genetic material, similar to any typical siblings. Identical twins is a term that is commonly used synonymously with monozygotic twins, as they both refer to twins that are genetically identical. However, the more precise and scientific term for twins arising from a single fertilized ovum is monozygotic, which is why it is considered the most accurate choice in this context.

Understanding these distinctions is essential for interpreting reproductive biology accurately, especially in fields like healthcare where genetic conditions might be relevant.