Bio1151b
Chapter
15
The Chromosomal Basis of Inheritance
Mendel's laws of
and independent
can be explained by the
theory of
inheritance.
Chromosomes undergo
and independent
during
meiosis.
Thomas Hunt
Morgan's
experiments with fruit
flies
(
) showed that the
eye-color
is sex-linked and located on the
chromosome.
A
dihybrid
cross with two phenotypes yielded a F1 generation with only the
phenotypes. A
then yielded a F2 generation with all 4 phenotypes.
The small number of offspring with
phenotypes implied that the
linkage
can be broken due to
over and
genetic
.
In humans and other mammals, the
sex
chromosomes
and
determine an organism's gender. X-linked
disorders
include color
blindness,
, Duchenne muscular dystrophy.
Sex-linked disorders exhibit peculiar inheritance patterns.
Fathers usually pass a
recessive
allele to his
as a
.
The carrier has a 50% chance of passing the disease to
her
.
If the carrier marries an affected male,
of the
offspring
will have the
disorder.
occurs when homologous chromosomes do not separate normally in
meiosis.
In mammalian females, one of the two X chromosomes in each cell is randomly
during embryonic development and can be seen as a compact
body.
A female heterozygous for an X-resident gene may show
phenotype.
Chromosome
damage
includes
, duplication, inversion, and
.