After the third dose -- given at age 6 months -- your child will be 80% to 85% immune to whooping cough for 3 to 5 years. Everyone -- including adults -- from age 11 up should receive a booster vaccine, called Tdap. It's a combined tetanus, diphtheria, and pertussis booster vaccine.
How many chromosomes are in the nucleus of an onion root cell? There are 8 chromosomes in the nucleus of an onion root cell. The cells are undergoing mitosis, during which the amount of DNA is doubled even as the number of chromosomes â¦ remains constant. How many chromosomes do onions have?
  3) Root tips have very rapid rate of mitosis.   4) The cells are very responsive to staining techniques.   5) The chromosomes are large and fewer in number. (Only 16 in a  cell have the diploid condition. The reason for mitosis occurring most commonly in the onion root tip is because the onion root tip is a rapidly growing area of the plant. + 2 others found this useful. Jada Nneji.