hello and welcome to today's talk about X inactivation we know that female have one additional X chromosome whereas male only have one the phenomenon of X inactivation in female somatic cells has indeed a function it prevents the cell from getting twice as many gene products as a male cell X I assemble eise's the inactivated x chromosome this whole process was first discovered by the geneticist Mary Lyon and it seems to take place in female mammalian somatic cells due to its Explorer X inactivation sometimes it's also called lionize ation but when does it take place at first we have the female zygote and it takes several cell divisions until one of the two X chromosomes randomly gets inactivated this occurs in an early embryonic stem cell stage but what is X inactivation and how does it work on a molecular level the inactivated x chromosome is highly methylated making it transcriptional inactive the inactivated x chromosome also called bar body is tightly packed condensed DNA which is also called heterochromatin so to sum it up histone modifications are included leading to the structure of the bar body where no transcription takes place all the transcripts in the female cell originated from the activated X chromosome thanks for listening and please feel free to ask questions in the comments