From DNA to Protein (flash) | Video | posavski-obzor.info
Describe the relationship between cells, chromosomes, genes, and DNA. print Print Cells include a special structure called the nucleus. The nucleus of a cell . Organize the following important terms based on size from smallest to largest: Chromatin, Nucleus, Chromosomes, Cell, Nucleosomes, Bases, DNA double helix. Kids learn about cell nucleus in the science of biology. is the control center of the cell, storing the DNA and hereditary information inside chromosomes.
They organize into chromosomes prior to the cell dividing. Pore - The pores are small channels through the nuclear envelope. They allow for smaller molecules to pass through such as messenger RNA molecules, but keep larger DNA molecules inside the nucleus. Ribosome - Ribosomes are made inside the nucleolus and then sent outside the nucleus to make proteins. Genetic Information The most important function of the nucleus is to store the cell's genetic information in the form of DNA.
DNA holds the instructions for how the cell should work. DNA stands for deoxyribonucleic acid. The molecules of DNA are organized into special structures called chromosomes. Sections of DNA are called genes which hold hereditary information such as eye color and height.
You can go here to learn more about DNA and chromosomes. RNA plays an important role in making proteins called protein synthesis or translation. Translation - The RNA is used to configure amino acids into special proteins for use in the cell. With a high powered microscope, scientists can see chromosomes.
They are usually in pairs and look like short little worms. What do they look like? When a cell is not dividing called the interphase of the cell cyclethe chromosome is in its chromatin form.
In this form it is a long, very thin, strand. When the cell begins to divide, that strand replicates itself and winds up into shorter tubes.
Before the split, the two tubes are pinched together at a point called the centromere. The shorter arms of the tubes are called the "p arms" and the longer arms are called the "q arms.
For example, one chromosome may contain information on eye color and height while another chromosome may determine blood type. Genes Within each chromosome are specific sections of DNA called genes. Each gene contains the code or recipe to make a specific protein. These proteins determine how we grow and what traits we inherit from our parents. The cytoplasm is found outside the cell's nucleus. A computer analogy is useful: The DNA contained in genes performs like software, telling the hardware in the cytoplasm what to do.Biology: Cell Structure (with Joanne Jezequel)
Specifically, it sends a message through the membrane that encloses the nucleus to entities called ribosomes in the cytoplasm to manufacture one or several of a wide range of proteins.
It is these proteins that actually do the work of making peas tall or short, or humans brown-eyed or blue-eyed. He found it while studying pus that had accumulated on the bandages of wounded soldiers. Miescher, along with other scientists, learned that DNA was a large molecule composed mostly of a type of sugar called deoxyribose, which is related to table sugar. They also found traces of phosphate, a chemical derived from the element phosphorous. But the most important discovery was that DNA also contained four substances called nucleotide bases.
These bases are adenosine, cytosine, guanine, and thymine, and they are abbreviated A, C, G, and T. Miescher suspected that these bases combined to form chemical messages, and in so doing he came close to discovering the genetic code that governs all life. In fact, later research has shown that the bases that compose DNA function exactly like an alphabet that encodes meaningful expressions. In the same way that the twenty-six letters of the English alphabet can be combined to form an enormous number of intelligible words, phrases, and sentences, the four letters of the genetic alphabet—A, C, G, and T—combine with each other to create chemical messages that are then transmitted to the ribosomes and other parts of the cell.
However, for a language to work as a method of communication, the various letters have to be associated with each other according to a set of rules. In human languages, these rules are called grammar and syntax. The genetic code also has a set of rules, but it took scientists a long time to discover exactly what it was.
The first clue came in the early part of the twentieth century when they found that in any DNA molecule the number of As must equal the number of Ts and the number of Cs must equal the number of Gs, but the number of A-T, C-G combinations does not have to be equal.
The importance of this piece of information, however, was not understood for almost fifty years until scientists developed a complete description of how the various components of a DNA molecule fit together.
This feat was accomplished by a process called X-ray crystallography, in which a substance is combined with salt and allowed to form crystals.
Nucleus and ribosomes
When these crystals are viewed under a powerful electron microscope, the structure of molecules becomes apparent. However, electron microscopes do not produce precise visual images of what they are focused on. Instead, they generate data that have to be interpreted. Two other scientists, American geneticist James Watson and British biophysicist Francis Crick, became aware of their work and began to construct a physical model of the DNA molecule.
The paper in which Watson and Crick published the results of their painstaking research has been recognized as one of the most revolutionary and influential documents in the history of science. Watson, Crick, and Wilkins each received a Nobel Prize for their work. Unfortunately, Franklin died before her invaluable contribution could be recognized in this way.
Recently, historians of science have finally begun to recognize that without Franklin's groundbreaking work, the discovery of the structure of the DNA molecule would have been delayed by years, if not decades. Watson and Crick concluded that the DNA molecule was shaped like a double helix, two strands spiraling around each other.
BBC - GCSE Bitesize: DNA, genes and chromosomes
A helix is the shape of a corkscrew. A double helix is the shape of two corkscrews, one intertwined with the other and curving parallel to it, like the railings of a spiral staircase. Another way to think of the double helix is to imagine a twisted rope ladder with rigid rungs, each rope forming a helix.
The easiest way to think about DNA is to start by splitting the two helices [the plural form of the word helix ] apart. Think of it as sawing down through the middles of the wooden rungs of a rope ladder. The result is two single ropes with half-rungs hanging off each rope. They serve as the four letters of the genetic alphabet. Opposite every T would be an A and vice versa and opposite every G would be a C and vice versa.
The question then arises: How can just four letters create code for the thousands of proteins that the body produces and the correspondingly large number of traits they govern? The answer lies in the astonishingly large number of A-T, C-G combinations, or base pairs as they are called, that make up a gene.
If all the DNA compacted into a cell were stretched out, it would be about seven feet long. DNA and RNA The sequences of DNA that make up genes communicate instructions to the ribosomes to manufacture proteins that work together to produce an organism's traits.
However, genes do not perform this function directly. First, a process called transcription must occur.
From Cell to DNA Teacher Sheet
In transcription, a single gene, which could contain thousands of base pairs, unravels from the chromosome on which it is located. The DNA that constitutes that gene then splits into its two complementary strands. A special type of protein called an enzyme moves along one of the strands letter by letter and creates a corresponding strand of a substance called ribonucleic acid RNA. Three of these bases—A, C, and G—are the same in both, but in place of thymine TRNA has a base called uracil, which is abbreviated with the letter U.
As the enzyme creeps along the gene's DNA, it transcribes each base it encounters into a corresponding base on the newly emerging strand of RNA. Once the strand of RNA has been completely transcribed, it travels through the membrane that encloses the cell's nucleus into the cytoplasm. There, it attaches itself to a ribosome, providing the instructions needed to manufacture a protein.
This process is called translation, and it works like this. The thousands of proteins that any organism contains are made up of various combinations of twenty substances called amino acids. Each three-letter sequence of RNA tells the ribosome to make one of these amino acids.