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Light micrograph of a human egg cell during fertilisation

As a human egg cell is fertilized, two chromosome-containing cellular structures (dotted circles, centre) merge into one — a process that often goes wrong. Credit: Pascal Goetgheluck/Science Photo Library

Developmental biology

The error-prone step at the heart of making an embryo

High-resolution imaging shows why the union between two sets of chromosomes goes awry as least as often as not.

After a sperm fertilizes an egg, the chromosomes of both unite into a single genome, if all goes according to plan. Now, observations of developing embryos show that this all-important process often goes awry — a finding that helps to explain why at least half of newly formed human embryos have the wrong number of chromosomes.

Some 50–70% of embryos have aneuploidy, an abnormal number of chromosomes. Such embryos are often miscarried.

To find out why aneuploidy is so common, Melina Schuh at the Max Planck Institute for Biophysical Chemistry in Göttigen, Germany, and her collaborators used high-resolution microscopes to observe the early stages of human and cow development. They discovered a crucial step: maternal and paternal genomes, which start off enclosed in their own structures, cluster around the location where they will fuse.

This clustering enables rapid and error-free unification of the two genomes. But this complex process has many steps that can go wrong. Failures lead to aneuploidy and fragments of nuclei containing subsets of chromosomes — both of which impair the development of healthy embryos.

More Research Highlights...

Camera-trap image of Dendrohyrax interfluvialis

Some tree hyraxes scream in the night, but the newly identified Dendrohyrax interfluvialis (above, camera-trap image) utters a complex series of squawks, rattles and barks. Credit: J. F. Oates et al./Zool. J. Linn. Soc.

Zoology

A bark in the dark reveals a hidden hyrax

Its neighbours scream, but a new species of tree hyrax — a cousin of the elephant — unleashes a rattling bark.
Plastic and other debris floats underwater in blue water

Plastic detritus from snacks and meals floats in the Red Sea. Marine sampling shows that food waste accounts for nearly 90% of plastic pollution at some locales. Credit: Andrey Nekrasov/Barcroft Media/Getty

Ocean sciences

Humanity’s fast-food habit is filling the ocean with plastic

Food bags, drink bottles and similar items account for the biggest share of plastic waste near the shore.
Conceptual artwork of a pair of entangled quantum particles.

An artist’s impression of ‘entangled’ particles, which share properties even at a distance. Entangled photons can be used to help secure a multi-party video meeting. Credit: Mark Garlick/Science Photo Library

Quantum information

Quantum keys dial up tamper-proof conference calls

A new experiment efficiently distributes the highly secure keys to four parties instead of the typical two.
Farmers harvest pineapples in a field.

Workers harvest pineapples in Lingao County, China. Less than one-third of the money spent on food eaten at home reaches farmers. Credit: Yuan Chen/VCG/Getty

Economics

Poor harvest: farmers earn a pitiful fraction of the money spent on food

The bulk of consumer food spending around the world ends up in the coffers of distributors, processors and other parties beyond the farm gate.
A woman wearing a protective face mask splashes her hands in a jet of water

A pedestrian seeks relief from searing temperatures in Spain, where a high proportion of heat-related deaths have been linked to climate change. Credit: SALAS/EPA-EFE/Shutterstock

Climate change

More than one-third of heat deaths blamed on climate change

Warming resulting from human activities accounts for a high percentage of heat-related deaths, especially in southern Asia and South America.
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