Investigating CSI – Background material Table of Contents I ...

These loci are located on the same chromosome for the female (left) and the
male (right). The upper locus can produce two different bands called 1 and 3.
The lower locus can produce bands called 2 or 4. The male is homozygous for
band 1 at the upper locus and 2 for the lower locus. The female is heterozygous
at both loci. Thier RFLP banding patterns can be seen on the Southern blot
below:
The male can only produce one type of gamete (1 and 2) but the female can
produce four different gametes. Two of the possible four are called parental
because they carry both RFLP bands from the same chromosome; 1 and 2 from
the left chromosome or 3 and 4 from the right chromosome. The other two
chromosomes are recombinant because recombination has occurred between
the two loci and thus the RFLP bands are mixed so that 1 is now linked to 4 and
3 is linked to 2.
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