Polytene chromosomes in salivary glands are formed as a result of:

The persistence of the nuclear envelope and the formation of an intranuclear spindle are characteristic of ..........

For a cell,$n \rightarrow 2n$ $(P)$ and $2n \rightarrow n$ $(Q)$. What are $P$ and $Q$?

What is a kinetochore?

Which of the following statements are correct?
$I -$ Mitosis occurs in both haploid and diploid cells.
$II -$ Meiosis occurs in both haploid and diploid cells.
$III -$ Mitosis occurs only in haploid cells.
$IV -$ Mitosis occurs only in diploid cells.
$V -$ Meiosis occurs only in haploid cells.
$VI -$ Meiosis occurs only in diploid cells.

Identify the incorrect statements:
$(1)$ Meiosis involves only a single cycle of $DNA$ replication.
$(2)$ At the end of Meiosis-$I$,four haploid cells are formed.
$(3)$ Mitosis is generally restricted to diploid cells.
$(4)$ In yeast,the cell cycle takes approximately $90$ minutes to complete.