Kønskromosom: Forskelle mellem versioner

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+"Det formodes at pattedyrs Y-kromosomet opstod for ca. 180 millioner år siden"
Linje 5:
Hannerne danner to typer sædceller, en type med et Y-kromosom og en type med et X-kromosom, og dette afgør afkommets køn.
 
Det formodes at pattedyrs Y-kromosometkromosom opstod for ca. 180 millioner år siden.<ref>[http://www.sciencedaily.com/releases/2014/04/140423151035.htm Swiss Institute of Bioinformatics. (2014, April 23). Male or female? First sex-determining genes appeared in mammals some 180 million years ago. ScienceDaily] Citat: "...The Y chromosome, which distinguishes males from females at the genetic level, appeared some 180 million years ago. It originated twice independently in all mammals..."</ref>
 
=== Mennesker ===