Module 2 - Chapter 2 - 2.1 Microscopy

Microscope

An instrument which enables you to magnify an object hundreds, thousands and even hundreds of thousands of time, there are three different types light microscopes, scanning electron microscopes and transmitting electron microscopes.

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Cells

The structural and functional unit of all living organisms.

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Chromosomes

A threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes, found inside the nucleus (or loose in the cell in bacteria). 

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Staining

When specimens viewed are treated with multiple stains to show different structures

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Fixing

Chemicals like formaldehyde are used to preserve specimens in as near-natural a state as possible.

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Sectioning

Specimens are dehydrated with alchols and then placed in a mould with wax or resin to form a hard block. This can then be sliced thinly with a knife called a microtome.

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Mounting

Where the specimens are secured to a microscope slide and a cover slip placed on top 

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Differential staining

Can distinguish between two types of organisms that would otherwise be hard to identify, it can also differentiate between different organelles of a single organism within a tissue sample

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Dry mount

Solid specimens are viewed whole/cut into very thin slices wit a sharp blade, this is called sectioning. The specimen is placed on the centre of the slide and a cover slip is placed over the sample e.g. hair, pollen, dust and insect parts.

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Wet Mount

Specimens are suspended in a liquid such as water or an immersion oil. A cover slip is placed on from an angle, this is a way used to view aquatic samples and other living organisms.

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Squash slides

A wet mount is first prepared and then a lens tissue is used to gently press down on the cover slip , potential damage to the cover slip can be avoided by squashing the sample between two microscope slides. This is a good technique for soft samples e.g. root tips.

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Smear Slides

The edge of a slide is used to smear the sample, creating a thin layer or even coating another slide. A cover slip is then placed over the sample, an example of a smear slide is a sample of blood.

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