Genetics · Module 3 · Sex determination, sex linkage and extranuclear inheritance

Sex Linkage and Extranuclear Inheritance Walkthrough

Mammals: one X in each female cell is inactivated , so both sexes have one active X.
Drosophila: the male doubles transcription of his single X (hyperactivation), using the MSL complex , which acetylates histone H4 on lysine 16 to open the chromatin.
C. elegans: XX hermaphrodites halve transcription of both X chromosomes using a condensin-like dosage compensation complex, matching XO males.

Watch sex chromosomes segregate, white-eyed flies cross both ways, nondisjunction prove the chromosome theory, X chromosomes coat themselves in XIST RNA, imprints switch genes off by parent, snail mothers set the coil of their young, and mitochondria pass only through eggs. Every calculation has an animated worked example. Nothing here is graded.

Speed

Think of it like this

Quick check

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