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[ home | about | about me | my BII project
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BII project 2 |contact | email | guestbook| links ] |
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Biology - The fundamental in
knowing DNA and Genes |
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| INTRODUCTION | |||||
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Proteins is a collection of amino acids. Amino acids is produced by ribosome and are the building blocks of proteins. A codon is a three-letter "word" that respresents a specific amino acid. Ribosome needs the information from mRNA in order to produced the amino acids. Messenger RNA (mRNA) is a special type of RNA that is made by the cell as a disposable copy of the DNA inside the nucleus. RNA is built from DNA. DNA always stay inside nucleus. RNA consists of 4 bases - A, C, G & U. DNA consists of another 4 bases - A, C, G & T. Living things are made of cells. Groups of cells are called tissues. Groups of tissues are called organs.
A QUICK OVERVIEW Forming of organsDNA -(contains)--> genes -(inside)--> chromosomes -(inside)--> nucleus -(inside)--> cell -(groups together)--> tissue -(groups together)--> organs Forming of protein DNA -(built)--> RNA -(to)--> mRNA -(input to)--> ribosome -(produces)-->codon -(representing)--> amino acids -(join together)--> protein
DNA DNA(Deoxyribonucleic acid) is often referred to as "the blueprint of life", implying that it contains all the information needed to create life. But this approach ignores the complex interactions between DNA and its cellular environment-interactions that regulate and control the spatial and temporal patterns of gene expression. DNA is nothing more than a pattern that tells the cell how to make its proteins. That is all that DNA does. A gene is simply a section of DNA that acts as a template to form an enzyme. DNA (Deoxyribonucleic acid) is a chemical structure that forms chromosomes. A piece of a chromosome that dictates a particular trait is called a gene. Structurally, DNA is a double helix: two strands of genetic material spiraled around each other. Each strand contains a sequence of bases (also called nucleotides). A base is one of four chemicals (adenine, guanine, cytosine and thymine). The two strands of DNA are connected at each base. Each base will only bond with one other base, as follows: Adenine (A) will only bond with thymine (T), and guanine (G) will only bond with cytosine (C). Suppose one strand of DNA looks like this: A-A-C-T-G-A-T-A-G-G-T-C-T-A-G
Together, the section of DNA would be represented like this: T-T-G-A-C-T-A-T-C-C-A-G-A-T-C
RNA DNA contains the information needed to create proteins, namely the amino acid sequences of these proteins. This information is transcribed into messenger RNA (Ribonucleic acid) - a molecule similar to DNA. DNA molecule takes the form of a linear code of four bases - A for adenine, C for cytosine, G for guanine, and T for thymine. RNA can also carry a linear code of four bases - A, C, G, and U for uracil. U replaces T as the base that complements A. Pairs of complementary bases form weak intermolecular chemical bonds with each other. A complements T, while C complements G. In RNA, U replaces T as the base that complements A. An organism's genome consists of the entire DNA contents for all the organism's genes, which are particular subsequences of the linear code. Each gene includes regulatory sequences and an open reading frame (ORF).- the sequence of DNA or RNA located between the start-code sequence (initiation codon) and the stop-code sequence (termination codon). The ORF is the sequence within the gene that, in a process called transcription - (the synthesis of an RNA copy from a sequence of DNA (a gene); the first step in gene expression), is copied from the ORF on the coding strand of DNA to molecules called messenger RNA (mRNA). Transcription occurs when an mRNA molecule is manufactured from the noncoding strand of DNA. since in mRNA, U replaces T as the bases that complments A, the mRNA therefore carries an exact copy of the ORF from the coding strand. Post-transcriptioal processing may splice out some subsequences of the mRNA molecule, called introns.
CHROMOSOME Chromosomes are tightly coiled microscope structure made up of mainly of DNA, which consists of four different building blocks called bases (A, T, C and G). The four bases are repeated millions of times to form each chromosome . Human chromosome range in length from 50 million to 263 millions bases with few exception (e.g. red blood cells), each of the trillions of cells in the human body contains a complete set of chromosomes - the genome. The entire human genome consists of 23 pairs of chromosomes with over 3 billion bases from each parent.
GENES
THE PROTEIN A protein is any chain of amino acids. An amino acid is a small molecule that acts as the building block of any protein. If you ignore the fat, your body is about 20-percent protein by weight. It is about 60-percent water. Most of the rest of your body is composed of minerals (for example, calcium in your bones). Amino acids are called "amino acids" because they contain an amino group (NH2) and a carboxyl group (COOH) that is acidic. The human body is constructed of 20 different amino acids (there are perhaps 100 different amino acids available in nature). As far as your body is concerned there are two different types of amino acids: essential and non-essential. Non-essential amino acids are amino acids that your body can create out of other chemicals found in your body. Essential amino acids cannot be created, and therefore the only way to get them is through food. Here are the different amino acids: Non-essential: Essential: Protein in our diets comes from both animal and vegetable sources. Most animal sources (meat, milk, eggs) provide what's called "complete protein", meaning that they contain all of the essential amino acids. Vegetable sources usually are low on or missing certain essential amino acids. For example, rice is low in isoleucine and lysine. However, different vegetable sources are deficient in different amino acids, and so by combining different foods you can get all of the essential amino acids throughout the course of the day. Some vegetable sources contain quite a bit of protein. Nuts, beans and soybeans are all high in protein. By combining them, you can get complete coverage of all essential amino acids. The digestive system breaks all proteins down into their amino acids so that they can enter the bloodstream. Cells then use the amino acids as building blocks to build enzymes and structural proteins. It turns out that all the As, Cs, Ts, and Gs are like a mini-alphabet that spells out messages for the cell. Different combinations of these letters spell out codes, and these codes tell the cell which specific proteins it should make. Proteins are important for all the workings of a cell and, in essence, control a great deal of what happens within a living organism. Proteins are also responsible for many of the traits that living things have. So the DNA molecule is responsible for passing heredity information by instructing the cell to make certain proteins that will influence the growth, development, and appearance of the living thing it is part of. The Protein Process An mRNA molecule travels out of the nucleus into the cytosol, where the molecule's code determines how proteins are manufactured. The messenger RNA carries instructions copied from the gene that are safe inside the nucleus out into the cytoplasm, where it searches for a ribosome protein factory. Ribosomes are the cell's protein factories. The mRNA attaches to a ribosome and directs it to manufacture the specific protein that the copied gene codes for. The next step is translation, which is the process by which a ribosome makes a protein using the information provided by the mRNA. The mRNA molecule's sequence is decoded to specify a sequence of 20 amino acids that form the protein's primary structure. A codon-a sequence of three bases drawn from A, C, G, and U-codes for an amino acid according to the genetic code. In a way, RNA and DNA speak the same language of a few letters. These three-letter codons each represent different amino acids. This is known as the genetic code. For example, AUG codes for the amino acid methionine(M), CGA codes for alanine(A), and ACC codes for threonine(T). Hence, the example mRNA fragment AUGGCAACC codes for the amino acid sequence MAT. By following the genetic code, the ribosome can manufacture the protein. As the ribosome starts to assemble the protein, it reads the first codon and obtains that amino acid. Then it continues down the line, and as each codon is read, a new amino acid is attached to the chain that is forming. When the ribosome reads the codon that tells it to stop, its job is finished. The resulting chain of amino acids constitutes a protein. Proteins are molecules essential to cell function. A protein may be an enzyme that catayzes a biochemical reaction, a cell structural component, a transducer that responds to the environment, or a regulatory element that empowers or inhibits some process within the cell.. Once manufactured, a protein folds into a 3-D shape whose geometric and chemical properties determine the protein's function.
What does a Protein do next ?
CELLS Cell Parts and Their Jobs Cell Part Job Description Cell membrane Security guard; check what goes in and out of the cellEndoplasmic reticulum Highway from the membrane to the nucleus Ribosomes Protein factories Golgi apparatus Storage and packaging centre; stores or snds new protein travelling; "customizes new proteins Lysosomes "Demolition workers"; break down unwanted materials in the cells Mitochondria Powerhouses; generate energy for the cell Nucleus The "brains" or control centre of the cell; houses hereditary material in the form of chromosomes, which contains genes, which are stretches of DNA, which code for proteins How do you get from DNA, made up of only four nucleotides, to an enzyme containing 20 different amino acids? There are two answers to this question: 1) An extremely complex and amazing enzyme called a ribosome reads
messenger RNA, produced from the DNA, and converts it into amino-acid
chains. |
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| Chromosome | |||||
| What is a chromosome?
Chromosomes are tightly coiled microscopic structures made up mainly of DNA, which consists of four different building blocks called bases (A, T, C, G). The four bases are repeated millions of times to form each chromosome. How big are human chromosomes? Human chromosomes range in length from 50 million to 263 million bases. With few exceptions (e.g., red blood cells), each of the trillions of cells in the human body contains a complete set of chromosomes--the genome. If all the bases in the human genome were spread out 1 millimeter apart, they would extend from Memphis to Los Angeles. How many chromosomes are in the human genome? The nucleus of most human cells contains two sets of chromosomes, one set given by each parent. Each set has 23 single chromosomes--22 autosomes and an X or Y sex chromosome. (A normal female will have a pair of X chromosomes; a male will have an X and Y pair.) What are the sizes of the individual human chromosomes and how many genes are estimated to be located on each? Chromosome #
Genes # of Bases
What are genes? What role do they play in disease research? Genes are chromosome pieces whose particular bases (e.g., ATTCGGA) determine how, when, and where the body makes each of the many thousands of different proteins required for life. Humans have an estimated 30,000 genes, with an average length of about 3,000 bases. Genes make up only around 3 percent of human DNA; the remaining DNA has important but still unknown functions that may include regulating genes and maintaining the chromosome structure. Researchers hunt for disease-associated genes by looking for base changes found only in the DNA of affected individuals. Numerous disorders and traits mapped to particular chromosomes are displayed in this Website. Some disorders, such as cystic fibrosis (chromosome 7) and sickle cell anemia (chromosome 11) are caused by base sequence changes in a single gene. Many common diseases such as diabetes, hypertension, deafness, and cancers have more complex causes that may be a combination of sequence variations in several genes on different chromosomes, in addition to environmental factors. How will knowing the human genome sequence affect medicine? Knowing the DNA sequence is important because it affects such attributes as appearance, response to particular medicines, and resistance to infections and toxins. It may even influence behavior. Some sequence variations also can cause or contribute to such disorders as those found on the chromosomes presented in this Website. These new data and powerful DNA analysis tools will usher in a new era of medicine that could allow doctors to detect disease at earlier stages, make more accurate diagnoses, and customize drugs and other medical treatments to fit an individual's own DNA sequence. The eventual understanding of a gene's normal functions and how the gene may change to cause or contribute to disease will lead to more focused and effective treatments with fewer side effects. | |||||
| The X chromosome in Sex | |||||
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As we know, humans have 46 chromosomes: two sets of 23 chromosomes each. One set was inherited from the mother and the other swt was inherited from the father.Most of these chromosomes are alike, except for those called X and Y. The Y chromosome is much smaller than the X. If a child-to-be inherits one X chromosome from the mother and another X chromosome from the father, it will be a girl. On the other hand, if a child inherits an X chromosome from the mother and a Y chromosome from the father, it will develop into a boy. Obviously, the mother can only contribute an X because this is the only type of sex chromosome that she has, being the mother. But about half of the father's sperm carries an X chromosome, and the other half contains a Y chromosome, so the father can contribute either. There's about a 50/50 chance for either a boy or a girl to develop. |
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| The Human Genome Project | |||||
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Goals of the project:
You might be wondering whose DNA scientists are using to map and sequence the human genome, because every one of us has veriations in our DNA. The answer is that the Human Genome Project is using different stretches of DNA from many different people, so the completed human genome will be a composite of more than one person. | |||||
| Genome Terms | |||||
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Allele -
Amino acid - Gene expression - Gene mapping - Genetic code - Mitosis - |
Alternative form of a genetic locus; a single allele for each locus is inherited from each parent (e.g., at a locus for eye color the allele might result in blue or brown eyes).
Group of closely related genes that make similar products. Determination of the relative positions of genes on a DNA molecule or chromosome. Information coded within the nucleotide sequences of RNA and DNA that specifies the amino acid sequence in the synthesis of proteins. It is the information on which heredity is based.
The process of nuclear division in cells that produces daughter cells
that are genetically identical to each other and to the parent cell.
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Ribonucleic acid (RNA) - Sequencing -
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A chemical found in the nucleus and cytoplasm of cells; it plays an important role in protein synthesis and other chemical activities of the cell. The structure of RNA is similar to that of DNA. There are several classes of RNA molecules, including messenger RNA, transfer RNA, ribosomal RNA, and other small RNAs, each serving a different purpose. Determination of the order of nucleotides (base sequences) in a DNA or RNA molecule or the order of amino acids in a protein. Undifferentiated, primitive cells in the bone marrow that have the ability both to multiply and to differentiate into specific blood cells. They can grow into any type of cell in the body, such as heart cells, blood cells, or brain cells.
The process in which the genetic code carried by mRNA directs the synthesis of proteins from amino acids. | ||||