Showing posts with label DNA. Show all posts
Showing posts with label DNA. Show all posts
July 18, 2011
Inherited alleles revealing an incestuous paternity.
Some rape cases result in the pregnancy of the victim and if the case is not reported to the police after the act with a subsequent gynaecological examination of the girl and the taking of a vaginal swab, there is no way of connecting the rape case with the perpetrator, except by parentage determination using DNA (deoxyribonucleic acid) analysis after abortion or induced delivery. In order to solve the rape case of a minor girl of 14 years which resulted with pregnancy, where a 60-year-old man was accused of the rape, DNA was extracted from blood samples from the girl and the putative assailant and from the foetus after its induced delivery. The autosomal short tandem repeats (STR) typing for 15 different loci showed differences in 6 STR loci between the putative assailant as a father and the foetus, thus excluding the tested paternity. A large number of identical loci between the mother's and the child's genotype led us to consider the possibility of incestuous paternity. Analysis of DNA samples from the girl's father and brother clarified the case as brother-sister incest. Key words: rape case, short tandem repeats (STRs) genotype, incest.
January 18, 2008
Genetics of eye color unveiled
It's been discovered that only a few "letters" of the six billion that make up the human genetic code are responsible for most of the variation in the color of human eyes.
The investigation, conducted by a team of scientists from Queensland, Australia, will be published in an upcoming issue of the American Journal of Human Genetics.
The findings are based on a genetic study of nearly 4000 people.
The differences in the color of the eyes are largely a "single nucleotide polymorphisms (SNPs - pronounced" snips "); variations in the sequence of letters that form a single strand of human DNA.
SNPs represent a change of just one letter in the genetic sequence. These changes, or mutations in our DNA may have important implications for the way the gene is expressed physically.
All SNPs are located near a gene called OCA2. This gene produces a protein that helps give hair, skin and the colour of his eyes. And OCA2 cause mutations in the most common type of albinism.
Brown and blue
The study, which focused on the twins, their brothers and their parents, it shows - conclusively - that there is a "gene" for the color of the eyes.
Everyone has two copies of a SNP. So there are a number of possible combinations, some of which are more strongly associated with, for example, blue eyes, with brown eyes.
In short, these combinations greatly influence the color of a person's eyes, but they are not the last word.
Dr. Richard Sturm and his colleagues found three HNS near the beginning of OCA2 gene that were associated with the color blue eyes.
"The SNPs that we have identified themselves are not functionally causing the change in eye color, but are linked very closely to something that is," Dr Sturm, of the University of Queensland, told BBC News.
"When OCA2 is eliminated, there is a loss of pigmentation. These SNP's position right at the beginning of the gene means that we are seeing a change in the regulation of the gene in people with color blue eyes."
Functional changes
So these SNPs, at the beginning of OCA2 probably regulate how much of the protein is produced by the pigmentation gene. People with brown eyes can have a lot of this protein, while people with blue eyes have less.
However, the only letter of the changes involved in the green eyes could produce functional changes in pigmentation of the protein.
The researchers found SNPs in another position in the region OCA2 - linked to the green eyes - which led to changes in the amino acids (the building blocks of protein).
"To use an analogy, one of the changes is like changing light and shuts down, while the other is how to change the bulb from brown to green," said Dr Sturm.
In total, the only letter of the changes identified in the study accounted for 74% of the total variation in the color of the eyes, researchers said.
The investigation, conducted by a team of scientists from Queensland, Australia, will be published in an upcoming issue of the American Journal of Human Genetics.
The findings are based on a genetic study of nearly 4000 people.
The differences in the color of the eyes are largely a "single nucleotide polymorphisms (SNPs - pronounced" snips "); variations in the sequence of letters that form a single strand of human DNA.
SNPs represent a change of just one letter in the genetic sequence. These changes, or mutations in our DNA may have important implications for the way the gene is expressed physically.
All SNPs are located near a gene called OCA2. This gene produces a protein that helps give hair, skin and the colour of his eyes. And OCA2 cause mutations in the most common type of albinism.
Brown and blue
The study, which focused on the twins, their brothers and their parents, it shows - conclusively - that there is a "gene" for the color of the eyes.
Everyone has two copies of a SNP. So there are a number of possible combinations, some of which are more strongly associated with, for example, blue eyes, with brown eyes.
In short, these combinations greatly influence the color of a person's eyes, but they are not the last word.
Dr. Richard Sturm and his colleagues found three HNS near the beginning of OCA2 gene that were associated with the color blue eyes.
"The SNPs that we have identified themselves are not functionally causing the change in eye color, but are linked very closely to something that is," Dr Sturm, of the University of Queensland, told BBC News.
"When OCA2 is eliminated, there is a loss of pigmentation. These SNP's position right at the beginning of the gene means that we are seeing a change in the regulation of the gene in people with color blue eyes."
Functional changes
So these SNPs, at the beginning of OCA2 probably regulate how much of the protein is produced by the pigmentation gene. People with brown eyes can have a lot of this protein, while people with blue eyes have less.
However, the only letter of the changes involved in the green eyes could produce functional changes in pigmentation of the protein.
The researchers found SNPs in another position in the region OCA2 - linked to the green eyes - which led to changes in the amino acids (the building blocks of protein).
"To use an analogy, one of the changes is like changing light and shuts down, while the other is how to change the bulb from brown to green," said Dr Sturm.
In total, the only letter of the changes identified in the study accounted for 74% of the total variation in the color of the eyes, researchers said.
January 2, 2008
DNA clues on the African origin of Chinese populations
Modern man, or Homo sapiens, might have migrated from Africa into China by way of Southeast Asia between 18000 and 60000 years, researchers say.
This latter finding, the search for Chinese scientists and their international colleagues concluded that modern humans might have moved from Africa to China to replace Mono erectus (archaic of walking upright human beings) , to become the ancestors of the country \ 'modern man.
The conclusion is based on the comparison and analysis of the Y chromosome using DNA samples of 88 existing populations in East Asia, Southeast Asia and Oceania , said Li Jin, one of the Chinese researchers of the study "Chinese Human Genome Diversity Project. \ "
Li Jin is a professor of both the National Human Genome Center in Shanghai and the Institute of Genetics, Fudan University.
Scientists have found that variations in the Y chromosome in northern China are derived from those in the south of China, the fact that a small number of settlers of African origin moved to the north of China because of the obstacle of the powerful Yangtze River. And Polynesians, who live in the islands of the Pacific Ocean, are found to have different Y chromosome in Taiwan, forcing scientists to reconsider the hypothsis that Polynesians are the descendants of the ancestors of Taiwanese aborigines.
In general, almost all Y-chromosome variations in East Asia and Oceania could be found among those in Southeast Asia, said Li Jin.
Therefore, the results also indicate that modern humans migrated from Africa to Southeast Asia almost 60000 years.
Subsequently, the migrants are believed to have headed for two directions: one moved north to the south of China before spreading in the country \ 's north across the river Yangtze, and the other went to Indonesia and finally reached the Oceania.
The Y-chromosome research is an important method for tracing the migration patterns of men and the results clearly show the relationships between groups of people in Southeast Asia and Asia and 'Oceania, according to another major Chinese researcher Jiayou Chu, a professor of the Chinese Academy of Medical Sciences.
The research result was published in today \ 's issuance of the Proceeding of National Academy of Sciences, an American journal.
The finding means that scientists have made progress in the pursuit of human origin, though the conclusion that human beings modern Chinese migrated from Africa remains controversial, "said Academician of the Academy Science Chinese Zhu Chen, who is also the director of Shanghai \ 'S National Human Genome Center.
In 1987, the United States \ 'scientists postponed a theory based on mitochondrial DNA evidence that all human beings from Africa and later migrated to other corners of the globe. Intentional in academia, few arguments were raised about the theory that all humanity palaeoanthropic originated in Africa. Meanwhile, scientists noted that the fossils of Peking Man who lived 500000 years ago and Yuanmao Man more than 1.7 million years old have been discovered in China, but both lack any direct link with hereditary Chinese modern man.
There is a disconnection or "faultage" in the fossil palaeoanthropic Chinese who lived some 60000 to 100000 years, researchers say.
Coinciding with the fossil record, Chinese scientists discovered last year that primitive elements of DNA found in modern Chinese are identical to those found in Africans.
The discovery has provided evidence of weight on the genetic basis of the theory that modern Chinese were not changed since the archaic-walking upright human beings in China, but from Africa.
This latter finding, the search for Chinese scientists and their international colleagues concluded that modern humans might have moved from Africa to China to replace Mono erectus (archaic of walking upright human beings) , to become the ancestors of the country \ 'modern man.
The conclusion is based on the comparison and analysis of the Y chromosome using DNA samples of 88 existing populations in East Asia, Southeast Asia and Oceania , said Li Jin, one of the Chinese researchers of the study "Chinese Human Genome Diversity Project. \ "
Li Jin is a professor of both the National Human Genome Center in Shanghai and the Institute of Genetics, Fudan University.
Scientists have found that variations in the Y chromosome in northern China are derived from those in the south of China, the fact that a small number of settlers of African origin moved to the north of China because of the obstacle of the powerful Yangtze River. And Polynesians, who live in the islands of the Pacific Ocean, are found to have different Y chromosome in Taiwan, forcing scientists to reconsider the hypothsis that Polynesians are the descendants of the ancestors of Taiwanese aborigines.
In general, almost all Y-chromosome variations in East Asia and Oceania could be found among those in Southeast Asia, said Li Jin.
Therefore, the results also indicate that modern humans migrated from Africa to Southeast Asia almost 60000 years.
Subsequently, the migrants are believed to have headed for two directions: one moved north to the south of China before spreading in the country \ 's north across the river Yangtze, and the other went to Indonesia and finally reached the Oceania.
The Y-chromosome research is an important method for tracing the migration patterns of men and the results clearly show the relationships between groups of people in Southeast Asia and Asia and 'Oceania, according to another major Chinese researcher Jiayou Chu, a professor of the Chinese Academy of Medical Sciences.
The research result was published in today \ 's issuance of the Proceeding of National Academy of Sciences, an American journal.
The finding means that scientists have made progress in the pursuit of human origin, though the conclusion that human beings modern Chinese migrated from Africa remains controversial, "said Academician of the Academy Science Chinese Zhu Chen, who is also the director of Shanghai \ 'S National Human Genome Center.
In 1987, the United States \ 'scientists postponed a theory based on mitochondrial DNA evidence that all human beings from Africa and later migrated to other corners of the globe. Intentional in academia, few arguments were raised about the theory that all humanity palaeoanthropic originated in Africa. Meanwhile, scientists noted that the fossils of Peking Man who lived 500000 years ago and Yuanmao Man more than 1.7 million years old have been discovered in China, but both lack any direct link with hereditary Chinese modern man.
There is a disconnection or "faultage" in the fossil palaeoanthropic Chinese who lived some 60000 to 100000 years, researchers say.
Coinciding with the fossil record, Chinese scientists discovered last year that primitive elements of DNA found in modern Chinese are identical to those found in Africans.
The discovery has provided evidence of weight on the genetic basis of the theory that modern Chinese were not changed since the archaic-walking upright human beings in China, but from Africa.
December 1, 2006
DNA Testing: An Introduction For Non-Scientists
"DNA Testing: An Introduction For Non-Scientists" is an excellent primary source of information for the non-scientist about the details, the how-to and the why about DNA testing and paternity. Check out this resource if you are serious about DNA testing. As a sample, here is the introduction. Find the complete article in http://www.scientific.org/tutorials/articles/riley/riley.html
Introduction:
DNA is material that governs inheritance of eye color, hair color, stature, bone density and many other human and animal traits. DNA is a long, but narrow string-like object. A one foot long string or strand of DNA is normally packed into a space roughly equal to a cube 1/millionth of an inch on a side. This is possible only because DNA is a very thin string.
Our body's cells each contain a complete sample of our DNA. One cell is roughly equal in size to the cube described in the previous paragraph. There are muscle cells, brain cells, liver cells, blood cells, sperm cells and others. Basically, every part of the body is made up of these tiny cells and each contains a sample or complement of DNA identical to that of every other cell within a given person. There are a few exceptions. For example, our red blood cells lack DNA. Blood itself can be typed because of the DNA contained in our white blood cells.
Not only does the human body rely on DNA but so do most living things including plants, animals and bacteria.
A strand of DNA is made up of tiny building-blocks. There are only four, different basic building-blocks. Scientists usually refer to these using four letters, A, T, G, and C. These four letters are short nicknames for more complicated building-block chemical names, but actually the letters (A,T, G and C) are used much more commonly than the chemical names so the latter will not be mentioned here. Another term for DNA's building blocks is the term, "bases." A, T, G and C are bases.
For example, to refer to a particular piece of DNA, we might write: AATTGCCTTTTAAAAA. This is a perfectly acceptable way of describing a piece of DNA. Someone with a machine called a DNA synthesizer could actually synthesize the same piece of DNA from the information AATTGCCTTTTAAAAA alone.
The sequence of bases (letters) can code for many properties of the body's cells. The cells can read this code. Some DNA sequences encode important information for the cell. Such DNA is called, not surprisingly, "coding DNA." Our cells also contain much DNA that doesn't encode anything that we know about. If the DNA doesn't encode anything, it is called non-coding DNA or sometimes, "junk DNA."[1]
The DNA code, or genetic code as it is called, is passed through the sperm and egg to the offspring. A single sperm cell contains about three billion bases consisting of A, T, G and C that follow each other in a well defined sequence along the strand of DNA. Each egg cell also contains three billion bases arranged in a well-defined sequence very similar, but not identical to the sperm.
Both coding and non-coding DNAs may vary from one individual to another. These DNA variations can be used to identify people or at least distinguish one person from another.
Introduction:
DNA is material that governs inheritance of eye color, hair color, stature, bone density and many other human and animal traits. DNA is a long, but narrow string-like object. A one foot long string or strand of DNA is normally packed into a space roughly equal to a cube 1/millionth of an inch on a side. This is possible only because DNA is a very thin string.
Our body's cells each contain a complete sample of our DNA. One cell is roughly equal in size to the cube described in the previous paragraph. There are muscle cells, brain cells, liver cells, blood cells, sperm cells and others. Basically, every part of the body is made up of these tiny cells and each contains a sample or complement of DNA identical to that of every other cell within a given person. There are a few exceptions. For example, our red blood cells lack DNA. Blood itself can be typed because of the DNA contained in our white blood cells.
Not only does the human body rely on DNA but so do most living things including plants, animals and bacteria.
A strand of DNA is made up of tiny building-blocks. There are only four, different basic building-blocks. Scientists usually refer to these using four letters, A, T, G, and C. These four letters are short nicknames for more complicated building-block chemical names, but actually the letters (A,T, G and C) are used much more commonly than the chemical names so the latter will not be mentioned here. Another term for DNA's building blocks is the term, "bases." A, T, G and C are bases.
For example, to refer to a particular piece of DNA, we might write: AATTGCCTTTTAAAAA. This is a perfectly acceptable way of describing a piece of DNA. Someone with a machine called a DNA synthesizer could actually synthesize the same piece of DNA from the information AATTGCCTTTTAAAAA alone.
The sequence of bases (letters) can code for many properties of the body's cells. The cells can read this code. Some DNA sequences encode important information for the cell. Such DNA is called, not surprisingly, "coding DNA." Our cells also contain much DNA that doesn't encode anything that we know about. If the DNA doesn't encode anything, it is called non-coding DNA or sometimes, "junk DNA."[1]
The DNA code, or genetic code as it is called, is passed through the sperm and egg to the offspring. A single sperm cell contains about three billion bases consisting of A, T, G and C that follow each other in a well defined sequence along the strand of DNA. Each egg cell also contains three billion bases arranged in a well-defined sequence very similar, but not identical to the sperm.
Both coding and non-coding DNAs may vary from one individual to another. These DNA variations can be used to identify people or at least distinguish one person from another.
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