Biology

88 problems

Circadian temperature compensation

Most chemical reactions change speed with temperature. A plant’s daily clock can keep nearly the same rhythm. How do its components cooperate to do that?

Human X-chromosome inactivation

Developing cells can silence much of one X chromosome. How do human embryos establish which copy becomes inactive?

Escape from X-chromosome inactivation

An inactive X chromosome is not completely silent. Why do some genes escape, and why does that vary between tissues and cells?

Mast seeding

Some plants produce huge seed crops together, then little for years. How do weather cues and stored resources set that rhythm?

Maintenance of sexual reproduction

Sexual reproduction can be costly compared with reproduction without a partner. Why does it persist so widely?

Genome size evolution

Closely related organisms can carry very different amounts of DNA. What determines how genomes expand or shrink?

Bacterial speciation

Bacteria exchange DNA across lineages. How do distinct evolutionary populations form and remain separate?

Cambrian explosion

Animal body plans diversified rapidly around the Ediacaran–Cambrian transition. What combination of changes drove that radiation?

Rangeomorph nutrition

Rangeomorphs were branching Ediacaran organisms. How did they obtain nutrients in the deep-sea settings where some lived?

Evolution of menopause

Some mammals live long after reproduction ends. Which evolutionary conditions make that unusual life history favorable?

Intra-Golgi transport

The Golgi modifies cargo as it moves through the organelle. How is that traffic coordinated with the recycling of its resident proteins?

Bulky cargo export from the ER

Some cargo is too large for a conventional small transport vesicle. How does it leave the endoplasmic reticulum?

Nuclear pore selectivity

Nuclear pores admit some molecules and exclude others. How does their dynamic central barrier adjust to the cargo passing through?

Mammalian cell size homeostasis

Different mammalian cells maintain different sizes. What sets their target size and coordinates growth with division?

Organ growth termination

Organs slow their growth and reach characteristic sizes. How do local signals and the rest of the body coordinate that stopping point?

Mitochondrial DNA bottleneck

A mother’s mix of mitochondrial DNA variants can change sharply between generations. What physical sampling process drives that change?

Biomolecular condensate function

Cells concentrate molecules in membraneless compartments. What makes their changing composition and material behavior useful for particular tasks?

Mitotic spindle self-organization

Spindles organize filaments to separate chromosomes. How do chromosome-attached bundles integrate with the spindle’s collective organization?

Mammalian replication origins

Mammalian DNA replication can begin at many licensed sites. What determines which sites actually start copying in a given cell?

Granulophagy

Most stress granules disperse when stress ends. How does autophagy recognize and remove the granules that persist?

Mitochondrial gene retention

Mitochondria keep some genes while many others reside in the nucleus. Why do different lineages retain different sets?

Meiotic homologue recognition

During egg formation in fruit flies, matching chromosomes must find one another. How do repeated DNA sequences help them recognize a match?

Insect photoperiodic timing

Insects use day length to prepare for seasonal dormancy. How do daily clock signals become a seasonal decision?

Co-translational membrane-protein folding

How do α-helical membrane proteins fold while they are made, as sequence, synthesis and the surrounding membrane determine their route?