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Genetyka (1157)

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! EN_90185030_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Action of designed enediynes: Last of 4 molecular graphics showing the cleavage of DNA by a synthetic enediyne (at top). A number of these compounds have been designed by K.C. Nicolaou & colleagues at the Scripps Research Institute, California, to mimic the selective anticancer properties of more complex naturally- occurring relatives. The enediynes are designed with functional groups that target the DNA & trigger a series of reactions that result in its breakage. The DNA model was produced by J.Macke for a video by M.Pique entitled ENEDIYNES: CHEMICAL WARFARE AGAINST CANCER.
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! EN_90185146_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY The double helix. Computer graphic illustration of the structure of DNA. The two helices of the structure are formed by alternating phosphate and sugar groups in the 'backbones'. At each sugar is a nucleic acid base (adenine, thymine, cytosine or guanine), pointing inward. Each base in one helix is fixed to a base in the opposite (or complimentary) helix by hydrogen bonding. In DNA, adenine in one helix always bonds to thymine in the other, likewise cytosine always bonds to guanine. This equivalence (known as Chargaff's Rule) is the key to DNA replication.
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! EN_90243639_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Illustration of the sex X chromosome carrying the anomaly associated with mental retardation known as fragile X syndrome. The anomaly consists of a slender thread (bottom left) which links the tip of the long arm to the rest of the X chromosome. Such chromosomes are easily broken which is the origin of the syndrome's name. Males, who have only one X chromosome in the cell nucleus, are usually affected while women may carry the genetic defect. They are able to transmit it to their sons, who may become affected, and daughters who in turn become carriers. The males affected are generally tall, have prominent noses and jaws, large testes and are prone to epileptic attacks.
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! EN_90226986_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Abstract computer graphics illustration of foetal development & human genetics. An image of a human foetus, at around 3 months development, is entwined by a short section of DNA, the molecule which dictates inherited characteristics. The background is formed by the banding patterns that comprise autoradiograms, the means by which scientists visualize & sequence the sections of DNA from chromosomes that constitute human genes.
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! EN_90185627_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Gene therapy: abstract illustration of a drug capsule filled with a short section of DNA (deoxyribonucleic acid), the genetic material of most living organisms. In background is a computer graphics image of a similar short section of DNA. DNA consists of two nucleotide strands twisted to form a double helix. The variable part of each nucleotide is 1 of 4 organic bases; adenine, thymine, guanine & cytosine, pairs of which connect the 2 strands. A precise sequence of DNA bases that instructs cells to make specific proteins is called a gene. In gene therapy, a gene responsible for an inherited disease would be identified, excised & replaced by a normal gene.
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! EN_90184795_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY 'Bionic mouse', an illustration by the artist Andrzej Dudzinski on the subject of genetic engineering. Published in 'The New Republic', 1989.
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! EN_90236960_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics illustration of a pair of sex chromosomes from a human male cell. In many species, sex determination is governed by the two sex chromosomes (X and Y). In mammals, some plants and a few insects, males are XY and females XX. In this case, the chromosome on the left is X and the one on the right is Y. Each cell in the human body contains 46 chromosomes; 22 matched pairs and the sex-determining pair. Chromosomes are made from proteins (principally histones), DNA and small amounts of RNA. The chromosomes carry the genes which determine the characteristics of the individual. A light micrograph of a set of chromosomes forms the background of this image.
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! EN_90185160_0002 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Schematic, computer graphics representation of the replication of DNA. Most cells reproduce through binary fission, with two daughter cells formed that are identical to their parent. Crick & Watson's model of DNA suggests that genetic information may be conserved if each of the 2 strands of parent DNA acts as a template for the polymerisation of a matching strand. In this way, the sequence of bases along the DNA molecule is preserved. Daughter DNA formed by complete separation of the parent strands consists of one new & one old strand; such a mechanism is termed seminconservative replication.
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! EN_90185160_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Schematic, computer graphics representation of the replication of DNA. Most cells reproduce through binary fission, with two daughter cells formed that are identical to their parent. Crick & Watson's model of DNA suggests that genetic information may be conserved if each of the 2 strands of parent DNA acts as a template for the polymerisation of a matching strand. In this way, the sequence of bases along the DNA molecule is preserved. Daughter DNA formed by complete separation of the parent strands consists of one new & one old strand; such a mechanism is termed seminconservative replication.
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! EN_90226462_0004 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics artwork featuring human chromosomes (X-shaped) and a cell nucleus (yellow, bottom right). Chromosomes are thread-like structures of the cell nucleus that carry genetic information in the form of genes. Each chromosome is seen to consist of two strands (chromatids) joined in a region known as the centromere or kinetochore. Each chromosome is capable of constructing an exact copy of itself whilst the cell is in its resting stage between successive cell divisions. When chromosome division occurs, the centromere splits longitudinally. The nucleus of every human cell contains 46 chromosomes, 23 of maternal & 23 of paternal origin.
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! EN_90185106_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Research on the human genome: composite image of an infant and a computer graphics model of the DNA molecule overlaid on a computer enhanced DNA sequencing autoradiogram. DNA sequencing of chromosomes involves decoding the base-pair sequence of sections of DNA - most usefully, those sections called genes which encode specific proteins. Sequencing and mapping - surveying each of the 23 pairs of human chromosomes to locate genes or other important markers - are two phases in the human genome project. The construction of such a complete genetic map involves a detailed biochemical survey of every gene expressed on all 23 pairs of human chromosomes.
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! EN_90228217_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Montage of a fluorescence micrograph of human chromosomes showing the mapping of cloned fragments of DNA (DNA probes), overlaid with the silhouette of an infant & a computer graphics model of the DNA molecule. The chromosomes are stained to give red fluorescence, with the DNA probes represented as small regions of green/yellow fluorescence. Mapping chromosomes may be regarded as a physical survey of each chromosome to find the location of genes or other markers. DNA mapping is one phase of the human genome project, an ambitious plan to reveal all of the genetic information encoded by every human chromosome.
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! EN_90185161_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics space-filling representation of a section of a DNA (deoxyribonucleic acid) molecule, the genetic material of most living organisms. The double helix of DNA may be regarded as a twisted ladder, the rungs of which are complementary pairs of organic bases; adenine pairs with thymine, cytosine with guanine. It is a precise sequence of DNA bases (a gene) which instructs cells to make a specific amino acid, chains of which form proteins. DNA is the major component of the chromosomes within a cell's nucleus and, through its control of protein synthesis, plays a central role in determining inherited characteristics. Image photographed on computer in Walter Gilbert's
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! EN_90185323_0010 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics space-filling representation of a section of a DNA (deoxyribonucleic acid) molecule, the genetic material of most living organisms. The double helix of DNA may be regarded as a twisted ladder, the rungs of which are complementary pairs of organic bases; adenine pairs with thymine, cytosine with guanine. It is a precise sequence of DNA bases (a gene) which instructs cells to make a specific amino acid, chains of which form proteins. DNA is the major component of the chromosomes within a cell's nucleus and, through its control of protein synthesis, plays a central role in determining inherited characteristics. Image photographed on computer in Walter Gilbert's
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! EN_90238262_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Illustration of a human sperm fertilising an egg. The picture shows the size difference between the egg, or ovum, & the spermatozoon. Human spermatozoa are extremely elongated single cells about 65 micrometres long, divided into 3 main regions: a head, neck, & tail. The head, which contains the male nucleus, is about 7 micrometres long. Here, the head appears buried in the follicular cells, which form the corona radia that surrounds the ovum. Beneath the corona radiata is a glycoprotein membrane, the zona pellucida, which the sperm must penetrate to reach the female nucleus. This version on black background. Version on white background is P648/010.
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! EN_90184748_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics representation of distamycin, an anticancer drug that binds to DNA (deoxyribonucleic acid). This image shows a complex of distamycin (shaded spheres) with a short stretch of DNA called a dodecamer (in schematic form). Distamycin binds in a narrow groove along the dodecamer and its presence results in distortions of the nucleic acid. The structure of the DNA dodecamer d(CGCAAATTTCGC) has been determined by Coll, Frederick, Wang & Rich (Proc. Natl. Acad. Sci. USA, 84, 8385-8389, 1987).
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! EN_90185143_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics image of DNA, showing its double helix structure. The DNA molecule's atoms are colour coded: carbon atoms are white, nitrogen blue, oxygen red, phosphorus green. DNA (deoxyrib- onucleic acid) consists of two linked strands of nucleotides, coiled into a helix.. The strands are joined by the pairing of organic bases on adjacent nucleotides. Each nucleotide contains the sugar deoxyribose & one of four bases: thymine (T), adenine (A), cytosine (C), guanine (G). T pairs up only with A, C with G. The genetic information is determined by the order of these pairs. The image shows the B form of DNA (B-DNA).
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! EN_90185159_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics image of DNA, showing its double helix structure. The DNA molecule's atoms are colour coded: carbon atoms are dark blue, nitrogen lighter blue, oxygen red, phosphorus green. DNA (deoxyribonucleic acid) consists of two linked strands of nucleotides, coiled into a helix. The strands are joined by the pairing of organic bases on adjacent nucleotides. Each nucleotide contains the sugar deoxyribose & one of four bases: thymine (T), adenine (A), cytosine (C), guanine (G). T pairs up only with A, C with G. The genetic information is determined by the order of the pairs. The image shows the B form of DNA (B-DNA).
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! EN_90185230_0001 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics image of DNA, showing its double helix structure & associated water molecules (green). DNA (deoxyribonucleic acid) consists of two linked strands of nucleotides (dark blue & purple), coiled into a helix. The strands are joined by the hydrogen bonding of pairs of organic bases (light blue & yellow) on adjacent nucleotid- es. The organic bases are thymine, adenine, cytosine, & guanine. The green circles show where water is likely to bind on the outside of the DNA molecule. Water serves a number of functions, & is involved in the interaction of DNA with proteins. The image shows the B form of DNA (B-DNA).
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! EN_90185230_0002 SCI
PHOTO: EAST NEWS/SCIENCE PHOTO LIBRARY Computer graphics image of DNA, showing its double helix structure & associated water molecules (green). DNA (deoxyribonucleic acid) consists of two linked strands of nucleotides (blue & red), coiled into a helix. The strands are joined by the hydrogen bonding of pairs of organic bases (purple & orange) on adjacent nucleotides. The organic bases are thymine, adenine, cytosine, & guanine. The green circles show where water is likely to bind on the outside of the DNA molecule. Water serves a number of functions, & is involved in the interaction of DNA with proteins. The image shows the B form of DNA (B-DNA).
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