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Comment by phreenet | Hacker News Reader

>One possibility was that Leonie had been storing sperm from her ex and using it to fertilise her eggs. But genetic testing showed that the babies only carried DNA from their mum, indicating they had been conceived via asexual reproduction.

In this form of asexual reproduction are the babies genetic clones of the mother?

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From BBC via Google's infobox;

  Asexual reproduction needs only one parent, unlike sexual reproduction,
  which needs two parents. Since there is only one parent, there is no
  fusion of gametes and no mixing of genetic information. As a result, the
  offspring are genetically identical to the parent and to each other. They
  are clones.

I haven't figured out if it is all sharks or not, but apparently in many previous observances the offspring have only been half clones of the mother. The genes all come from the mother, the offspring just ends up with less genetic diversity than the mother. The technical term is "automictic parthenogenesis". https://en.wikipedia.org/wiki/Parthenogenesis#Automictic_par...

>just ends up with less genetic diversity than the mother

"just"...

In humans, even a small loss in genetic variability such as cousin mating 1.5% is bad enough that we have laws against it in nearly every society.

Charles II, the last Habsburg king of Spain, had lost 25% genetic diversity and was mentally and physically disabled, and infertile. This genetic loss is equivalent to parent-offspring or sibling mating.

Some animals, like lab mice, can survive without genetic diversity, but they are much less fit and difficult to raise. Your half clone would have lost nearly 100% of its genetic diversity. A near-full clone mechanism exists which would preserves genetic diversity. We'd have to sequence this shark to find out.

Genetic diversity is meaningless at an individual level.

An organism may end up with 2 copies of a defective gene and demonstrate problems. However, having two working copies of the same segment is not a problem.

>In humans, even a small loss in genetic variability such as cousin mating 1.5% is bad enough that we have laws against it in nearly every society.

I thought this sounded suspicious, so I looked it up, and it's not true. Cousin marriage is legal in all of Europe, Australia and New Zealand, South America, Canada, Mexico, the Middle East, Russia, and India.

In The USA, cousin marriage is allowed in 17 states. But 40 out of the 50 states allow cousin sexual relations and cohabitations.

The only places in the world that cousin marriage is illegal is in China, Korea, Japan and some states in the US.

Whatever you think of cousin mating, it's just not true that "we have laws against it in nearly every society." In fact, just the opposite, it is allowed in nearly every society.

During my undergrad studies in anthropology, a prof remarked off-hand that the prohibition of first-cousin marriage a pretty new and baseless thing, and that the offspring were very negligibly at risk. It was an off-hand comment, but an off-hand comment made by someone with a PhD in the field, so I'm with her on this one. But now googling . . .

I did see once a documentary on a spider, where if there were no males to reproduce with, the female would hatch a single male spider that was a clone, and that spider would then fertilise her eggs before being devoured.

"... parthenogenetic offspring may have anywhere between all and half of the mother's alleles. The offspring having all of the mother's genetic material are called full clones and those having only half are called half clones. Full clones are usually formed without meiosis. If meiosis occurs, the offspring will get only a fraction of the mother's alleles."[1]

[1] https://en.wikipedia.org/wiki/Parthenogenesis

If you're referring to the shark in the news article, her offspring are not genetic clones.

"In sharks, asexual reproduction can occur when a female’s egg is fertilised by an adjacent cell known as a polar body, Dudgeon says. This also contains the female’s genetic material, leading to “extreme inbreeding”, she says."

Which is odd because genetic clones would be far healthier than the inbred offspring from above.

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