Bio3400
Chapter 5
Chromosome Mapping in Eukaryotes
Genes
independently
if they are on different
chromosomes
but show
if they are on the same
chromosome.
Genes on the same chromosome would
produce
gametes if
between nonsister chromatids occurs during meiosis.
Genes located
to each other on the same chromosome are
less
likely
to have
cross-over
events
occur between them.
The
frequencies between linked genes provide an estimate of the
between
them
(interlocus distance) and can be used to construct a chromosome
.
The percentage of
involved in an exchange between two genes is
the percentage of recombinant gametes
produced.
A
crossover
(SCO) alters linkage between two genes only if the crossover occurs
those two genes.
crossovers
(DCOs) can be used to determine the order of
genes on the chromosome.
The
mapping
technique can be used to map three
genes in one
cross
by two
methods.
As the distance between linked genes increases, the mapping
accuracy
due to undetected multiple crossovers that can be predicted by a
distribution.
The large numbers of mutants in
has allowed extensive chromosome
mapping
in this and other organisms such as maize and mice.
Mapping in maize using
markers established that crossing over involves a
exchange
of chromosome regions.
In
Drosophila
, homologs can pair up during
, allowing mitotic
recombination
to take place.
Agents that induce chromosome
increase the frequency of sister
exchange
(SCE) during
but do not produce recombination.
In
Neurospora
, meiosis produces eight
ordered
haploid
within an
, allowing ordered
analysis.
Somatic cell
can be used for
testing
in which a specific gene product can be correlated with a
chromosome.