Instrumentation 6

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Microscopy is the study of objects or samples that are too small to be seen by the naked eye. There are several types of microscopy, each with its own advantages and limitations. Here are the main types of microscopy: 1. Optical microscopy: This is the most common type of microscopy, which uses visible light to illuminate a sample. Optical microscopy can be further divided into several subtypes, such as brightfield, darkfield, phase contrast, fluorescence, and confocal microscopy. Optical microscopy is a technique that uses visible light to observe the sample under a microscope. It consists of several components, including an objective lens, an eyepiece lens, and a light source. The working of optical microscopy involves the following steps. The sample to be viewed is prepared by fixing it onto a glass slide and adding a stain or dye to enhance its contrast. The light source, located beneath the sample, emits light that is directed through the condenser lens to focus the light o...
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Different types of DNA.

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DNA (Deoxyribonucleic acid) is a complex molecule that carries genetic information in living organisms. DNA is made up of building blocks called nucleotides, which are composed of a sugar molecule, a phosphate group, and a nitrogenous base. The four nitrogenous bases that makeup DNA are adenine (A), thymine (T), guanine (G), and cytosine (C). The order of these bases, known as the DNA sequence, determines the genetic information encoded in DNA. There are different types of DNA, including:



  • B-DNA: 

B-DNA is the most common form of DNA, which is found in cells during normal physiological conditions. It is a right-handed double helix with ten base pairs per helical turn. The nitrogenous bases are stacked on top of each other, and the sugar-phosphate backbone twists around the axis of the helix. B-DNA is stable and is not easily disrupted by changes in temperature, pH, or salt concentration.
  • A-DNA: 
A-DNA is a right-handed double helix with 11 base pairs per helical turn. It is wider and shorter than B-DNA, and the nitrogenous bases are tilted concerning the axis of the helix. A-DNA is less stable than B-DNA and is typically found in conditions where the DNA molecule is under stress, such as when it is bound to proteins.
  • Z-DNA: 
Z-DNA is a left-handed double helix with 12 base pairs per helical turn. The nitrogenous bases are tilted and zigzagged concerning the axis of the helix. Z-DNA is less common than B-DNA and A-DNA and is typically found in regions of DNA that are rich in the nucleotide cytosine. Z-DNA is involved in gene regulation and is thought to play a role in the immune response.
  • Cruciform DNA: 
Cruciform DNA is a type of DNA structure that occurs when DNA strands fold back on themselves, forming a four-way junction. Cruciform DNA is involved in gene regulation and is thought to play a role in DNA replication and repair.


  • Supercoiled DNA: 
Supercoiled DNA is DNA that has been twisted upon itself, forming a more compact structure. Supercoiling is an important mechanism for compacting DNA within cells, as well as for regulating gene expression and DNA replication.


In summary, DNA is a complex molecule with many different structures and functions. The different types of DNA structures reflect the versatility and adaptability of this molecule, and they play important roles in regulating gene expression, DNA replication, and other biological processes.

 

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