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From: RonO <rokimoto557@gmail.com>
Newsgroups: talk.origins
Subject: Largest animal genome 91 billion base-pairs.
Date: Wed, 21 Aug 2024 14:51:59 -0500
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https://www.nature.com/articles/s41586-024-07830-1

paywalled, but Science news article:

https://www.science.org/content/article/odd-fish-has-30-times-much-dna-humans-new-record-animals

They have just identified the new largest animal genome, but unlike 
amphibians that duplicated their whole genomes over and over to create 
their large genomes this lobe-finned fish (a species of lungfish) 
enlarged it's genome by failing to regulate the multiplication of 
transposons.  It has a 91 billion  base-pair genome, but still only as 
many genes as related lobe-finned fish (lobe-finned fish gave rise to 
tetrapods).  It has roughly the same number of genes that humans have, 
but it's genome is 30 times larger.  Allowing transposons to run rampant 
has increased it's genome size with copies of transposons by about 3 
billion base-pairs every 10 million years.

Transposons are parasitic bits of DNA that can replicate and move from 
place to place in the genome.  Because of their parasitic nature they 
have been lumped into junk DNA, but they often do have functional genes, 
and take their own transcription regulatory sequences with them when the 
hop around the genome, so they have some function, but it isn't geared 
to helping out the host.  They just use the host cells to keep 
replicating more copies of themselves.  Jumping into genes causes 
genetic diseases and jumping around genes can cause differential 
regulation of the surrounding genes, so they cause insertion mutations 
that do affect the organism, but like other mutations, most of the 
mutations are benign, some of them are bad, and a few of them may do 
some interesting things.  At this time for this lungfish probably nearly 
all new transposition events are likely messing up existing transposon 
sequence.  About 90% of the genome seems to be transposon sequence at 
this time, but my guess is that most of the remaining 90% is just old 
transposon sequence that has been mutated to the extent that they can't 
recognize the fragments as once being transposons.

Ron Okimoto