The Effect of Fast Neutrons on Chromosomes in Meiosis and Its Bearing upon Pachytene Pairing.

REVIOUS experiments have shown that quantitatively the response P of chromosomes of Vicia faba in pachytene to X-rays is approximately the same as that of the same species at the onset of the somatic prophase (MARSHAK 1939a). CREIGHTON (1941) using methods similar to those employed in the Vicia studies found that meiotic chromosomes are only a sixth as sensitive as the mitotic chromosomes in Chorthippus. SAX and SWANSON (1941) have asserted that meiotic chromosomes of Tradescantia are more sensitive to X-rays than mitotic, although the meiotic stages used in their comparison are not identified. The experiments reported here show that the somatic chromosomes of Vicia faba a t the onset of the somatic prophase have the same sensitivity to neutrons as chromosomes in pachytene.