Scientific illustration

Oocyte and sperm

Size is only one of the ways in which sperm and oocytes differ drastically. In fact, the oocyte is the largest cell in the human body, while the sperm is the smallest!

Thesis cover art

I created this image for my PhD thesis cover. It represents the innate curiosity of a child, so similar to that of scientific researchers figuring out how the world works.

Oocyte maturation

Oocytes arrest in the early stages of meiosis before birth. From puberty, oocytes start growing, and one or two fully grown oocytes are ovulated each month: after years in Prophase I, the oocytes resume meiosis, only to arrest again (Metaphase II). Astonishingly, oocytes only truly finish meiosis if a sperm cell fertilizes them.

Cohesin complexes in mitosis & meiosis

Chromatids must be physically held together to withstand the spindle's pulling forces during metaphase and only separate at the right moment, in anaphase. Cohesin complexes form rings around chromatin, holding chromatids together.

Chromosome segregation in mitosis & meiosis

Cohesin is removed in a stepwise manner both in mitosis and meiosis: first from chromosome arms, then from the centromeric region. Both the molecular pathways involved and the timing of Cohesin removal differ between these divisions.

Cohesin removal in mitosis

In vertebrate mitotic cells, Cohesin is removed in two ways: (1) through the prophase pathway, which opens the Cohesin ring, and (2) through cleavage by the Separase protease.

Spindle assembly checkpoint

The Spindle Assembly Checkpoint (SAC) regulates anaphase onset by halting the cell in metaphase until all chromosomes are correctly attached to spindle microtubules. When all attachments are correct, the SAC is silenced, and Separase becomes active.

Kinetochore structure

Kinetochores are large, multilayered protein complexes that connect chromosomes to microtubules with the goal of carrying the chromosomes to opposite sides of the cell. Chromosome alignment and segregation require stable microtubule binding to the chromosome's kinetochore.

Initial chromosome capture and conversion to end-on attachment

Chromosomes are more likely to encounter the lateral walls of microtubule fibers than their tips. When end-on attachments form they are corrected several times until only end-on and tension-bearing attachments remain.