Mitosis and the cell cycleEdexcel A-Level Biology A: Flashcards

What these 14 flashcards ask

What is the cell cycle?
What happens in the S phase?
What are sister chromatids?
What happens in prophase?
What happens in metaphase?
What happens in anaphase?
What happens in telophase?
Why does mitosis produce genetically identical cells?
Give two uses of mitosis in organisms.
How is mitotic index calculated?
Why is the tip of the root used in a squash?
Why is the root tip warmed in hydrochloric acid?
Why is the root tip squashed under the coverslip?
Name one disadvantage of asexual reproduction.

Exam questions on Mitosis and the cell cycle

A student prepares a root tip squash from garlic roots to observe the stages of mitosis. She cuts the last few millimetres from the tip of a root, warms it in hydrochloric acid, adds a stain that binds to DNA, and then squashes it under a coverslip before viewing it with a light microscope.
State the purpose of (i) warming the root tip in hydrochloric acid and (ii) adding the stain.2 marks
Using a light microscope, the student examines a root tip squash and counts 200 cells. She finds 168 cells in interphase, 14 in prophase, 6 in metaphase, 4 in anaphase and 8 in telophase. The whole cell cycle in this species takes 18 hours.
Calculate the mean time that a cell in this root tip spends in mitosis. Give your answer in hours to two significant figures.2 marks
A chemotherapy drug prevents spindle fibres from forming. Tumour cells exposed to the drug are found with condensed chromosomes, each made of two chromatids, scattered through the cell. The cells do not divide and many later die.
Explain why chromosomes cannot be separated into two daughter nuclei when spindle formation is prevented.3 marks

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).