Question

what is dense tangled of threads in the nucleus

Answer 1

Hii..

Those are the chromosomes i.e the genetic material present in the nucleus .
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Hope this helps!

Answer 2

Nucleus is a spherical or oval protoplasmic body, which is a much denser than the cytoplasm. ... Inside the nucleus there is a tangled mass of thread-like structures called chromatin. When a cell starts to divide, the chromatin appears as long threads and finally, rod-like bodies called chromosomes.