Week 1

Question 1

What are the basic components of the original cell theory?

Answer 1

1. All organisms are composed of cells
2. The cell is the basic unit of life
3. Cells are produced by the division of pre-existing cells

Question 2

What are the principles of the modern cell theory?

Answer 2

1. Cells contain hereditary information that can be passed on
2. All cells are essentially comprised of the same chemical mix
3. Cells carry out all the basic chemical and physiological processes within themselves (movement digestion etc.)
4. Cellular activity depends on the activities of subcellular structures

Question 3

What is the difference between euchromatin and heterochromatin?

Answer 3

Euchromatin: is light coloured, loose, open chromatin allowing for active transcription and gene expression

Heterochromatin: is dark coloured, dense, tightly packed chromatin that is indicative of transcriptionally inactive regions of DNA

Question 4

What are the main imaging techniques for macro imaging?

Answer 4

1. Ultrasonography:
   - uses sound waves to image different tissue densities
   - Often used to image developing babies
2. Optical projection tomography:
   - passes visible light through an embryo which has been rendered semi transparent
   - used in research to view internal structures in 3D (usually mouse models)
3. 3D Morphometric analysis:
   - Using images from ultrasound or OPT measurements are taken

Question 5

What are the main micro imaging techniques?

Answer 5

1. Light microscopy:
   - First technique discovered
   - Max resolution is 400-600nm
   - Uses stained cells e.g. h&e stain
2. Confocal microscopy:
   - takes slice of specimen to view one focal plane in very high resolution
   - often uses fluroescence stains e.g. DAPI (to stain DNA)
   - can be used to view subcellular structures
   - can also be used to image whole mount images of embryos
3. Electron microscopy:
   - Much higher resolution (not limited by wavelength of visible light)
   - can image internal cell structures e.g. mitochondria

Question 6

Why are alcohols and xylene used before applying a coverslip to a slide?

Answer 6

• Alcohol is used as a dehydrating agent to remove water from the specimen and then xylene is used as a clearing agent to remove alcohol from the section

Question 7

What do the following stains colour?

• heamotoxylin
• eosin
• alcian blue

Answer 7

• heamotoxylin: stains nucleus purple
• eosin: stains cytoplasm pink
• alcian blue: stains connective tissues blue