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Puzzeled? Lost? Going in circles?
Do you need a map?
Well, come right in and we will lead you...
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Welcome to my DNA Fun Things, Puzzles & Junk Page
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Mapping and Sequences: (Credit for this information goes to: Microsoft Encarta 2001 Encyclopedia)
There are two main categories of gene-mapping techniques: linkage, or genetic, mapping , a method that identicfies only the relative order of genes along a chromosome; and physical mapping, a group of more precise methods that can place genes at specific distances from one another on a chromosome. Both types of mapping use genetic markers, dtectable physical or molecular characteristics that differ among individuals and that are passed from one generation to the next.
Linkage mapping was developed in the early 1900s by American biologist and geneticist Thomas Hurt Morgan. By observing how frequently certain characteristics were inherited in combination in numerous generations of fruit flies, he concluded that traits that were often inherited in combination must be assiciated with genes that were near one another on the chromosome. From his studies, Morgan was able to create a rough map showing the relative order of these associated genes on the chromosomes, and in 1933 he was awarded the Nobel Prize in physiology or medicine for his work.
Human linkage maps are created mainly by following inheritance patterns in large families over many generations. Originally, these studies were limited to inherited physical traits that could be observed easily in each family member. Today, however, sophisticated laboratory techniques allow researchers to create more detailed maps by comparing the position of the target gene relative to the order of gentic markers, or specific known segments of DNA.
Physical mapping determines the physical distance between landmarks on the chromosomes. The most precise physical mapping techniques combine robotics, lasers, and computers to measure the distance between genetic markers. For these maps, DNA fragments are then duplicated numerous times in the laboratory so that the resulting identical copies, called clones, can be tested individually for the presence or absence of specific genetic landmarks. Those clones that share several landmarks are likly to come from overlapping segments of the chromosome. The overlapping regions of the clones can then be compared to determine the overall order of the landmarks along the chromosome and the exact sequence in which the cloned pieces of DNA originally existed in the chromosome.
Very detailed physical maps that indicate the precise order of cloned pieces of a chromosome are required to determine the actual sequenec of nucleotides. The Human Genome Project most commonly uses the DNA sequencing method developed by British biochemist and two-time Nobel laureate Frederick Sanger. In Sanger's method, specific pieces of DNA are replicated and modified so that each ends in a fluorescent form of one of the four nuceotides. In modern automated DNA sequencers, the modified nuceotide at the end of such a chain is detected with a laser, and the exact number of nucleotides in the chain is determined. This information is then combined by computer to reconstruct the sequence of base in the original DNA molecule.
Duplicating DNA accuratley and quickly is of criticla importance to both mapping and sequencing. Scientists first replicated fragments of human DNA by cloning them in single-celled organisms that divide rapidly, such as bacteria or yeast. This technique can be time consuming and labor-intensive. In the late 1980s, however, a revolutionary method of reproducing DNA, known as the polymerase chain reation (PCR), came into widespread use. PCR is easily automated and can copy a single molecule of DNA many millions of times in a few hours. In 1993 American biochemist Kary Mullis was awarded the Noble Prize in chemistry for originating this technique.
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This newspaper article talks about the scientists that have discovered something next to the four letter chemicals in a DNA structure. After overlooking the substance, they have noticed that it is not human, animal or even the four-letter chemical. So, they considered it "JUNK." Soon they noticed it was not junk and was doing something remarkable, it was reproducing (cloning) itself! Yes, it was junk making more junk! For no completely clear reason, genes seem to cluster in GC rich regions, while so called junk or repetitive DNA generally confines itself to AT zones.
It also talks about the public gene mappers that have "theories" on how male mutation has twice as much as female mutation. They came to the conclusions of this by comparing the genetic sequences of the X and Y-chromosomes. Women have two X's and men have X and a Y. With more facts to come to conclusion, they believe it's because men make billions of sperm, while women are born with far fewer eggs, only a few hundred of which mature in a lifetime.
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Staying alive counting your JUNK DNA!
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Please email me with any questions or comments.
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(This page was mapped out on 04/12/01)
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