The diagram below shows a fern from the family Ophioglossaceae, commonly known
as adder’s-tongue ferns.
There are many species in this family. Some of the species have different diploid numbers
of chromosomes. The diploid numbers range from 240 to 1250 chromosomes.
A student investigated the relationship between diploid number and the proportion
of time spent by cells in different phases of the cell cycle.
She prepared root tip squashes from Ophioglossaceae species with different numbers
of chromosomes. She then determined the stage of mitosis of each cell in a sample
from each species.
Describe how the root tip squash could be prepared and used to identify the stage of
mitosis of each cell in a sample.
1. suitable stain named ;
2. acid treatment of root tip ;
3. maceration / suitable description ;
4. correct use of slide and coverslip ;
5. idea that (darkly) stained chromosomes can be seen when cells observed through a microscope ;
6. idea that stage of mitosis can be determined by observing the position of the chromosomes ;