Organisation of tissues

Question 1

organisation of multicellular organisms

Answer 1

-A collection of cells makes up tissues
-A collection of tissues makes up an organ
-A collection of organs makes up an organ system

Question 2

Squash root tip practical

Answer 2

-Aim is to investigate cells undergoing mitosis by preparing a root tip squash
METHOD
1.Use the growing root tips of a plant e.g an onion
2. Cut about 5mm from the root tip as this is where cells are actively dividing (mitosis)
3. Place the root tip in hydrochloric acid for five minutes at 60 degrees celsius
-This will break down the cell walls and make it easier to squash later
4. Rinse off the root tip with cold water to stop the acid reaction
5.Add the root tip to a slide and add an acetic orcein stain
-The stain binds to the DNA in the root tip, staining the chromosomes so they are more visible
6. Cover the root tip with a cover slide and gently push the cover slide down with a blunt object e.g a mounting needle
7. Observe the cells undergoing mitosis : prophase, metaphase, anaphase, telophase