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DNA only exists in the form of chromosomes at particular parts of a cell's life (namely, cell division) and is a highly organized structure consisting of DNA an
by araneae 17y ago
DNA only exists in the form of chromosomes at particular parts of a cell's life (namely, cell division) and is a highly organized structure consisting of DNA and of proteins.
Neither sperm nor photoreceptors undergo cell division, so for all its existence its DNA exists in an undifferentiated mass inside the cell. DNA is long, but skinny, so it compacts quite nicely.
- ugh 17y agoCool. But that also means that photoreceptor cells and sperm divide from cells quite unlike themselves, right? Or does that work differently?
- amoeba 17y agoStem cells are totipotent and can give rise to any type of specialized cell in your body. Cell signaling induces horribly complex signaling pathways that lead to profound changes in transcription of that cell's DNA. As an embryo, your gonads start in your chest and, through signals from your brain, end up in your pelvic region. Erythrocytes (Red blood cells) are a great example of specialization. Before they become erythrocytes they have a nucleus. Their nucleus is ejected, their shape completely changes from spherical to flat-with-a-dimple and they are not a red blood cell. Obviously, erythrocytes cannot divide.
- ugh 17y agoThanks for the explanation!
- amoeba 17y agoCells are great. You're welcome.
- kirubakaran 17y agoNo wonder you, amoeba, think so.
- araneae 17y agoSpiders are better.