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What I understand is- I think this is picture of DNA. But why is it in this conformation ? What types of cells have this type of DNA ?
It is called a Holliday junction. It forms during recombination.
A microscope is an instrument that magnifies an object so that it may be seen by the observer. Because cells are usually too small to see with the naked eye, a microscope is an essential tool in the field of biology. In addition to magnification, microscopes also provide resolution, which is the ability to distinguish two nearby objects as separate. A combination of magnification and resolution is necessary to clearly view specimens under the microscope. The light microscope bends a beam of light at the specimen using a series of lenses to provide a clear image of the specimen to the observer.
In this lab, parts of the microscope will be reviewed. Students will learn the proper use and care of the microscope and observe samples from pond water.
The many branches of biology
Although there are only four unifying principles, biology covers a broad range of topics that are broken into many disciplines and subdisciplines.
On a high level, the different fields of biology can each be thought of as the study of one type of organism, according to "Blackie's Dictionary of Biology" (S Chand, 2014). For example, zoology is the study of animals, botany is the study of plants and microbiology is the study of microorganisms.
Within those broader fields, many biologists specialize in researching a specific topic or problem. For example, a scientist may study behavior of a certain fish species, while another scientist may research the neurological and chemical mechanisms behind the behavior.
There are numerous branches and subdisciplines of biology, but here is a short list of some of the more broad fields that fall under the umbrella of biology:
- Biochemistry: The study of the chemical processes that take place in or are related to living things, according to the Biochemical Society. For example, pharmacology is a type of biochemistry research that focuses on studying how drugs interact with chemicals in the body, as described in a 2010 review in the journal Biochemistry.
- Ecology: The study of how organisms interact with their environment. For example, an ecologist may study how honeybee behavior is affected by humans living nearby.
- Genetics: The study of heredity. Geneticists study how genes are passed down by parents to their offspring, and how they vary from person to person. For example, scientists have identified several genes and genetic mutations that influence human lifespan, as reported in a 2019 review published in the journal Nature Reviews Genetics.
- Physiology: The study of how living things work. Physiology, which is applicable to any living organism, "deals with the life-supporting functions and processes of living organisms or their parts," according to Nature. Physiologists seek to understand biological processes, such as how a particular organ works, what its function is and how it's affected by outside stimuli. For example, physiologists have studied how listening to music can cause physical changes in the human body, such as a slower or faster heart rate.
Photo 51 is an X-ray diffraction image of a paracrystalline gel composed of DNA fiber  taken by Raymond Gosling,   a graduate student working under the supervision of Rosalind Franklin in May 1952 at King's College London, while working in Sir John Randall's group.     The image was tagged "photo 51" because it was the 51st diffraction photograph that Franklin and Gosling had taken.  It was critical evidence  in identifying the structure of DNA. 
James Watson was shown the photo by Maurice Wilkins of Kings College, after Raymond Gosling, the author of the picture, had returned to working under Wilkins' supervision. Rosalind Franklin did not know this at the time because she was leaving King's College London. Randall, the head of the group, had asked Gosling to share all his data with Wilkins.  Along with Francis Crick, Watson used characteristics and features of Photo 51, together with evidence from multiple other sources, to develop the chemical model of the DNA molecule. Their model, and manuscripts by Wilkins and colleagues, and Gosling and Franklin, were first published, together, in 1953, in the same issue of Nature. In 1962, the Nobel Prize in Physiology or Medicine was awarded to Watson, Crick and Wilkins. The prize was not awarded to Franklin she had died four years earlier, and although there was not yet a rule against posthumous awards,  the Nobel Committee generally does not make posthumous nominations.  Likewise, Gosling's work was not cited by the prize committee.
The photograph provided key information that was essential for developing a model of DNA.   The diffraction pattern determined the helical nature of the double helix strands (antiparallel). The outside of the DNA chain has a backbone of alternating deoxyribose and phosphate moieties, and the base pairs, the order of which provides codes for protein building and thereby inheritance, are inside the helix. Watson and Crick's calculations from Gosling and Franklin's photography gave crucial parameters for the size and structure of the helix. 
Photo 51 became a crucial data source  that led to the development of the DNA model and confirmed the prior postulated double helical structure of DNA, which were presented in the series of three articles in the journal Nature in 1953.
As historians of science have re-examined the period during which this image was obtained, considerable controversy has arisen over both the significance of the contribution of this image to the work of Watson and Crick, as well as the methods by which they obtained the image. Franklin had been hired independently of Maurice Wilkins, who, taking over as Gosling's new supervisor, showed Photo 51 to Watson and Crick without Franklin's knowledge. Whether Franklin would have deduced the structure of DNA on her own, from her own data, had Watson and Crick not obtained Gosling's image, is a hotly debated topic,     made more controversial by the negative caricature of Franklin presented in the early chapters of Watson's history of the research on DNA structure, The Double Helix.    Watson admitted his distortion of Franklin in his book, noting in the epilogue: "Since my initial impressions about [Franklin], both scientific and personal (as recorded in the early pages of this book) were often wrong, I want to say something here about her achievements." 
# What Does “Image of God” Mean? (Part 3)
One of the portraits the New Testament paints of Jesus is that of ultimate image-bearer of God. Jesus fully reflects God’s image he is the true representative of God in his creation. No one embodies more fully this truly human quality.
We can begin where we left off previously, with Psalm 8. This psalm praises God for how he has exalted humanity: man is a little lower than God, crowned with glory and honor, and everything has been placed under his feet. Humankind, in other words, is one step below God, given authority to rule creation. Psalm 8 is fully consistent with Genesis 1:26-27 where “image of God” is described as ruling over all of creation.
In Hebrews 2:5-9, the anonymous author cites Psalm 8 for a reason that might not be obvious at first glance: Jesus ranks higher than angels, a topic he began in 1:5. (In fact, all of Hebrews is one long “Jesus is better than…” argument, e.g. Moses, the high priest, and the tabernacle.)
Psalm 8 supports his argument. Creation was not subject to angels, but humankind. The author of Hebrews reminds us that “everything” is put under human royal authority—everything is subject to humans (v. 8). But the author of Hebrews laments, “Yet at present we do not see everything subject to him” (v. 8). The “him” refers to humanity. What we do see, however, is Jesus who is now crowned with glory and honor because of his death (v. 9).
It is not to angels that he has subjected the world to come, about which we are speaking. But there is a place where someone has testified: “What is man that you are mindful of him, the son of man that you care for him? You made him a little[a] lower than the angels you crowned him with glory and honor and put everything under his feet.” In putting everything under him, God left nothing that is not subject to him. Yet at present we do not see everything subject to him. But we see Jesus, who was made a little lower than the angels, now crowned with glory and honor because he suffered death, so that by the grace of God he might taste death for everyone.
Jesus, who is like his brothers and sisters in every way (2:17), is the “ultimate human” because everything really is under his authority. The lofty status of humanity as God’s royal image-bearers, however true, is not fully realized in humanity as a whole. It is fully realized in Jesus as, paradoxically, the crucified and resurrected Son of God.
Jesus is the true image-bearer. You might say that Jesus is the only truly and fully human figure who has ever lived. By looking at the crucified and risen Son, we see what “human” really means, not the corrupted dysfunctional version that stares back us from the mirror, or that we see in others.
Colossians 1:15-20 (see side-bar) makes the same point in a different way. Jesus is the “image of the invisible God” (v. 15): he rules creation because all things were created by him. It is understandable to read this passage and think it is only focusing on Jesus’ divinity, but that would be missing half the point. As the resurrected son, Jesus is “head of the body, the church, the beginning and firstborn from among the dead” (v. 18). By his resurrection, Jesus is the first to embody fully the image-bearing role conferred on all humanity in Genesis.
Jesus does this not for himself, but for those who would come after, the people of God. Jesus is not simply “over all creation.” He is “firstborn over all creation” (v. 15). Christians, in other words, go along for the ride. As firstborn over creation he sees to it that those born after would achieve that same status. Simply put, in his resurrection, Jesus “completes” Genesis 1:26-27, for him and for us.
For this reason he had to be made like his brothers in every way, in order that he might become a merciful and faithful high priest in service to God, and that he might make atonement for the sins of the people.
This theme is already announced at the beginning of Hebrews, 1:1-4. In the past, God had spoken through prophets, but now he is speaking through the Son he himself has appointed. The echo of Psalm 2, where Israel’s king is God’s appointed Son, is confirmed in v. 5 where the author cites Psalm 2:7. As Son, Jesus is the newly appointed Davidic king, the representative ruler. But this Son takes it up a notch: he is the “radiance of God’s glory and the exact representation of his being.” Jesus is God’s representative ruler like no other.
The image of God in Genesis is not about “what makes us human,” such as one’s soul. It is about the lofty role God has given humankind to be his representative rulers. That is what image means: nothing more—but nothing less.
He is the image of the invisible God, the firstborn over all creation. For by him all things were created: things in heaven and on earth, visible and invisible, whether thrones or powers or rulers or authorities all things were created by him and for him. He is before all things, and in him all things hold together. And he is the head of the body, the church he is the beginning and the firstborn from among the dead, so that in everything he might have the supremacy. For God was pleased to have all his fullness dwell in him, and through him to reconcile to himself all things, whether things on earth or things in heaven, by making peace through his blood, shed on the cross.
Understood this way, we can and should speak of the image of God as marred, incomplete, subject to sin in all of us. The true image of God is only realized in the crucified and risen Son of God. And this gives us a much fuller understanding of the incarnation. The incarnate Son of God is fully God and fully human.
Jesus is the full image-bearer of God. He is the most human of any human who has ever lived. By faith, we too participate in restored humanity. Next week we will look at what that means for us today.
In this lecture about digital image analysis, Nico Stuurman describes how digital cameras for microscopes work, what a “pixel” is, Nyquist sampling, the dynamic range, noise, and color cameras. The features of an image are described, included bit-depth, intensity scaling and histograms, file formats and basic image processing.
- According to Nyquist sampling, which camera pixel size will be a reasonable match for a microscope with 250 nm resolution and 100x magnification?
- 25 μm
- 2 μm
- 8 μm
- 250 μm
- 50 μm
- Photon shot noise scales linearly with the number of photons
- Quantum efficiency in a ccd camera is the the probability in which an absorbed photon will be converted to an electron.
- Color cameras are less light efficient than black-and-white cameras.
- A 16 bit image must be scaled to 8 bit to be displayed on a monitor.
A pixel is a square (or dot) of uniform color in an image. The size of a pixel can vary, and the resolution of an image is the number of pixels per unit area. Although resolution is defined by area, it is often described using a linear measurement—dots per inch (dpi). Thus, 300 dpi indicates a resolution of 300 pixels per inch by 300 pixels per inch, which equals 90,000 pixels per square inch (1).
High-resolution digital cameras (in 2004) can acquire an image that is 6 megapixels in size. This can generate an image of approximately 2400 × 2400 pixels, or 8 inches × 8 inches at 300 dpi. Note that, with the right settings in Photoshop, physical size and resolution can be traded off against each other without a gain or loss in the amount of information—that is, you can resize an image without altering the total number of pixels.
You should be aware of the resolution at which the image was acquired by the digital camera on your microscope. When that file is opened in Photoshop, you have the option of setting the size and resolution of the image. You should not set the total number of pixels to be greater than that in the original image otherwise, the computer must create data for you that were not present in the original, and the resulting image is a misrepresentation of the original data—that is, the dpi of an image can only be increased if the size of the image is reduced proportionately.
It is acceptable to reduce the number of pixels in an image, which may be necessary if you have a large image at high resolution and want to create a small figure out of it. Reducing the resolution of an image is done in Photoshop by sampling the pixels in an area and creating a new pixel that is an average of the color and brightness of the sampled ones. Although this does alter your original data, you are not creating something that was not there in the first place you are presenting an average.
Is the 5-second Rule True or a Myth?
The 5-second rule is based on the theory that food that has been dropped on the floor for a brief period of time does not pick up many germs and is safe to eat. This theory is somewhat true in that the less time food is in contact with a surface, the fewer bacteria are transferred to the food. Several factors play a role in the level of contamination that may occur once food has been dropped on the floor or another surface. These factors include the texture of the food (soft, sticky, etc.) and the type of surface (tile, carpet, etc.) involved. It is always best to avoid eating food that has a high risk of contamination, such as food that has been dropped in the trash.
What is RNA?
Let&rsquos begin with the basics. Deoxyribonucleic acid (DNA) is a molecule you may already be familiar with it contains our genetic code, the blueprint of life. This essential molecule is the foundation for the &ldquocentral dogma of biology&rdquo, or the sequence of events necessary for life to function. DNA is a long, double-stranded molecule made up of bases, located in the cell&rsquos nucleus. The order of these bases determines the genetic blueprint, similar to the way the order of letters in the alphabet are used to form words. DNA&rsquos &lsquowords&rsquo are three letters (or bases) long, and these words specifically code for genes, which in the language of the cell, is the blueprint for proteins to be manufactured.
To &lsquoread&rsquo these blueprints, the double-helical DNA is unzipped to expose the individual strands and an enzyme translates them into a mobile, intermediate message, called ribonucleic acid (RNA). This intermediate message is called messenger RNA (mRNA), and it carries the instructions for making proteins. The mRNA is then transported outside of the nucleus, to the molecular machine responsible for manufacturing proteins, the ribosome. Here, the ribosome translates the mRNA using another three-letter word every three base pairs designates a specific building block called an amino acid (of which there are 20) to create a polypeptide chain that will eventually become a protein. The ribosome assembles a protein in three steps &ndash during initiation, the first step, transfer RNA (tRNA) brings the specific amino acid designated by the three-letter code to the ribosome. In the second step, elongation, each amino acid is sequentially connected by peptide bonds, forming a polypeptide chain. The order each amino acid is crucial to the functionality of the future protein errors in adding an amino acid can result in disease. Finally, during termination, the completed polypeptide chain is released from the ribosome and is folded into its final protein state. Proteins are required for the structure, function, and regulation of the body's tissues and organs their functionality is seemingly endless.
Throughout the latter half of the 20th century, we believed that RNA&rsquos primary role was to intermediate between DNA and protein, as we described above. Over the last three decades, those long-held beliefs have been shattered. We have witnessed amazing discoveries with regards to RNA biology, many of which have come from our own labs here at the RTI. In 1998, Andrew Fire and the RTI&rsquos Craig Mello discovered RNA interference (RNAi), in which double-stranded RNA can find and turn off specific genes based on certain sequences (order of the 'words'). For this, they earned the Nobel Prize in 2006! To understand more about RNAi and learn how we are developing this tool into a therapeutic platform, please see: What is RNAi?
This is an official Page of the University of Massachusetts Medical School
RNA Therapeutics Institute (RTI) &bull 368 Plantation St Worcester, Massachusetts 01605
Data must be reported directly, not through a filter based on what you think they “should” illustrate to your audience. For every adjustment that you make to a digital image, it is important to ask yourself, “Is the image that results from this adjustment still an accurate representation of the original data?” If the answer to this question is “no,” your actions may be construed as misconduct.
Some adjustments are currently considered to be acceptable (such as pseudocoloring or changes to gamma settings) but should be disclosed to your audience. You should, however, always be able to justify these adjustments as necessary to reveal a feature already present in the original data.
We hope that by listing guidelines and publicizing examples of transgressions, all of us can become more vigilant, particularly in guiding junior colleagues and students away from the tempting dangers of digital manipulation. Just because the tools exist to clean up sloppy work digitally, that is no excuse to do sloppy work.
If you would have redone an experiment to generate a presentation-quality image in the days before the digital age, you should probably redo it now.
Watch the video: Guess the Zoomed in Image! #1 Hard (August 2022).