Exams › NEET › Biology

In Down's syndrome, Karyotyping has shown that the disorder is associated with trisomy of chromosome number-21 usually due to

1. non-disjunction during egg-cell formation
2. non-disjunction during sperm-cell formation
3. non-disjunction during formation of egg-cells and sperm-cells
4. addition of extra chromosome during mitosis of the zygote

Correct answer: non-disjunction during egg-cell formation

Solution

Down syndrome most commonly results from meiotic nondisjunction producing an egg with two copies of chromosome 21. After fertilization by a normal sperm, the zygote has three copies of chromosome 21.

Related NEET Biology questions

• Pea plants were more suitable than cattle for Mendel's experiment because
• Identify the wrong statement about meiosis.
• Which condition of zygote cell will lead to birth of a normal human female child
• A human zygote has
• DNA in the offsprings is contributed by
• A common test to find the genotype of a hybrid is by

⚔️ Practice NEET Biology free + battle 1v1 →