A Genetic Test
X-Ray irradiation of a female
may induce recessive lethal
on one of the two X
chromosomes in reproductive cells in her germ line. When mated to
un-irradiated male, some
of her daughters will be heterozygous for the X' chromosome with the recessive
lethal (X'X). When these X'X
daughters are back-crossed to the un-irradiated hemizygous males (XY),
of the male embryos will inherit the unmutated maternal X and half will inherit the
lethal X' .
latter males die in early development,
females will have only
proportion of male offspring.
curve of X-ray
rate of induced mutation is linear,
which suggests that there is no lower limit (threshold) of
that does not produce some mutagenic effect. Chronic low-level
to radiation in other species (including humans) has been
implicated in a variety of medical conditions, including cancer.