In message .com,
Raphanus writes

Stewart Robert Hinsley wrote:
In message .com,
Raphanus writes

Different alleles are often, but not universally, of the same length. In
some cases they are distinguished by one or more base pair
substitutions. In others they are distinguished by the insertion or
deletion of lengths of DNA.

OK. Now in a heterozygous gene the two alleles would have to be of
the same length - right?

No.

Otherwise there would be a "kink" in one
strand of the DNA spiral (?).

No. I think you're confusing diploid genomes with double helices. The
two alleles in a diploid genome are on different chromosomes (DNA
molecules plus associated proteins).

Sometimes there are multiple copies of a gene on a single chromosome
(for example the ribosomal RNA arrays), but they're not in the same
position on opposite strands. One strand has coding (or junk) DNA, and
the other has complementary DNA. (Different genes can be on different
strands.) To a first approximation both strands are the same length; in
particular a deletion or insertion occurs on both strands. The function
of the complementary DNA is to act as a template for replication of the
coding DNA.

I appreciate your answers. They give me
much to "chew on."


--
Stewart Robert Hinsley