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17.2 Mapping Genomes
Researchers used the natural transfer of DNA from a plant to a plant host to introduce fragments of their choice into the plant host.
The Ti plasmid has a link to the plant cell's genome.
The Ti plasmids can be manipulated to remove the genes that cause the tumors.
Researchers can use antibiotic resistance genes from the Ti plasmids to grow E. coli cells as well.
There are many insect species that affect plants that are toxic to the bacterium Bt.
Bt toxin needs to be eaten by insects in order to be activated.
Within a few hours, insects that have eaten Bt toxin stop feeding on plants.
The insects die within a couple of days after the toxin is activated.
Plants have been given the ability to make their own Bt toxin that can be used against insects.
Scientists have cloned genes from Bt and introduced them into plants.
Bt toxin is safe for the environment and can be used as a natural pesticide.
The first GM crop was a tomato.
Scientists used antisense technology to slow the rotting process of GM tomatoes, which resulted in increased shelf life.
The tomato's flavor was improved by additional genetic modification.
The Flavr Savr tomato was not able to stay in the market because of shipping problems.
The maps that we use to navigate streets are similar to the maps that genome mapping creates.
Similar to an interstate highway map, genetic maps give the big picture and use genetic markers.
The linkage analysis was called by early geneticists.
Similar to a detailed road map, physical maps present the intimate details of smaller chromosomes.
Genetic linkage maps and physical maps are required to build a genome's complete picture.
It is easier for researchers to study individual genes with a complete genome map.
Human genome maps can be used to identify human diseasecausing genes.
We can use genome mapping to clean up pollutants or even prevent pollution.
Plants that better adapt to climate change may be the result of research into plant genome mapping.
The term linkage was used by scientists.
The early geneticists relied on observing the changes in the organisms' genes.
The idea of genes being linked by their location on the same chromosomes was first proposed by the father of modern genetics.
The first genetic maps were based on linkage analysis.
Studies of the offspring of parents with different traits led to the observation that certain traits were always linked.
In garden pea experiments, researchers discovered that the flower's color and plant pollen's shape were related, and that the genes that make up these traits were in close proximity to each other.
Linkage analysis is a study of the recombination frequencies between genes.
The genes are linked if the recombination frequencies are less than 50 percent.
There may be different locations on the chromosomes.
Recombination between genes A and B is more frequent than between genes B and C. It is more likely that they will collide.
Markers are required for the generation of genetic maps, just as markers are required for a road map.
Early genetic maps used genes as markers.
More sophisticated markers, including those based on non-coding DNA, are being used by scientists to compare people's genomes.
The individuals of a given species are not the same.
Every person has a set of characteristics.
Minor differences in the genome are useful for genetic mapping.
A good genetic marker is a region on the chromosomes that shows variation in the population.
We can detect RFLPs when a restriction endonuclease is used to cut the DNA of an individual and generate a series of fragments, which we can analyze using gel electrophoresis.
Every individual's genetic make up will give rise to a unique pattern of bands when cut with a particular set of restriction endonucleases.
The unique banding pattern will be created by certain chromosome regions that are subject to polymorphism.
There are repeated sets of nucleotides in the non-coding regions.
Non-coding, or "junk," DNA has no known biological function; however, research shows that much of it is transcribed.
It is active and may be involved in regulating coding genes.
The number of repeats may be different in individual organisms.
The repeat unit of microsatellites is very small.
There are variations in a single nucleotide.
Natural increases or decreases in the amount of recombination in the genome area affect genetic maps.
Some parts of the genome show a propensity for recombination, while others don't.
It's important to look at the information developed by multiple methods.
A physical map shows the distance between genetic markers and the number of nucleotides.
Scientists use three methods to create a physical map.
The amount of radiation can be adjusted to create smaller or larger fragments.
The technique overcomes the limitation of genetic mapping and we can adjust the radiation so that it doesn't affect it.
A sequence tagged site is a unique sequence in the genome that is used to generate a physical map.
AnEST is a shortSTS that we can identify with cDNA libraries, while we getSSLPs from known genetic markers, which give a link between genetic and physical maps.
A map shows the appearance of a chromosomes after scientists stain it and examine it under a microscope.
There are genetic maps and physical maps.
It's easy to understand why genome mapping technique types are important to show the big picture.
Scientists combine information from each technique to study the genome.
Different model organisms are being used for research.
As researchers develop more advanced techniques, they expect more breakthrough in genome mapping.
It is similar to completing a complicated puzzle using every piece of available data.
GenBank is a database at the National Center for Biotechnology Information that holds mapping information from laboratories all over the world.
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