There are at least two aspects to having a genetic disease. The first is mutations (which are present in genes and disrupt some function of the body) are random, non-conscious events that are part of your thrownness (i.e. the state in which you exist); they can occur before you were born or during your lifetime. Nobody (including yourself) is responsible for the mutation, it just is.
The non-conscious origin for mutations implies that the mutation is beyond your control, all pervasive and you are locked within its walls.
This brings the second aspect of genetic disease to mind. Many other genes have worked (and continue to work) to build and maintain a brain and a body capable of consciousness, free will and the ability to choose. Living with a mutation does not mean being the mutation; your other 30,000 genes create space for you to choose a reaction and be alongside the mutation and what befalls you in life. This is your true genetic identity...
Showing posts with label What is DNA?. Show all posts
Showing posts with label What is DNA?. Show all posts
Thursday, 19 September 2013
Wednesday, 11 September 2013
Autobiography - the structure and function of DNA (part 4)
DNA and Disease
DNA is fundamental in building a functioning body. It is also responsible for maintaining and defending the body against "the thousand natural shocks flesh is heir to". It is perhaps unsurprising that mutations in DNA cause disease.
There are around 200 different types of cell in the human body. All cells (except red blood cells) contain the entire complement of human DNA; however, some areas of DNA are active and generate proteins only in specific cells. Therefore, mutations in these areas will only affect these cells. Alternatively, some areas of DNA are active in all cells but different cells are susceptible to different environmental stress and this exaggerates the affect of the mutation in these cells. For example, substantia nigra nerve cells are lost in Parkinson's disease; these cells are under high oxidative stress and any mutations that cause extra stress will preferentially affect the substantia nigra.
DNA ("nature") and the environment ("nurture") are likely to play some part in all disease; some diseases are weighted towards DNA as cause (e.g. Huntington 's disease) while others are caused primarily by our surroundings (e.g. liver disease due to alcohol consumption). Parkinson's disease is likely to be somewhere in the middle with many subtle genetic factors interacting with the environment to cause loss of nerve cells.
See Nature 421 395-453
DNA is fundamental in building a functioning body. It is also responsible for maintaining and defending the body against "the thousand natural shocks flesh is heir to". It is perhaps unsurprising that mutations in DNA cause disease.
There are around 200 different types of cell in the human body. All cells (except red blood cells) contain the entire complement of human DNA; however, some areas of DNA are active and generate proteins only in specific cells. Therefore, mutations in these areas will only affect these cells. Alternatively, some areas of DNA are active in all cells but different cells are susceptible to different environmental stress and this exaggerates the affect of the mutation in these cells. For example, substantia nigra nerve cells are lost in Parkinson's disease; these cells are under high oxidative stress and any mutations that cause extra stress will preferentially affect the substantia nigra.
DNA ("nature") and the environment ("nurture") are likely to play some part in all disease; some diseases are weighted towards DNA as cause (e.g. Huntington 's disease) while others are caused primarily by our surroundings (e.g. liver disease due to alcohol consumption). Parkinson's disease is likely to be somewhere in the middle with many subtle genetic factors interacting with the environment to cause loss of nerve cells.
See Nature 421 395-453
Tuesday, 10 September 2013
Autobiography - the structure and function of DNA (part 3)
Mutations in DNA
Although the double helix structure of DNA allows for remarkably faithful and accurate replication, mistakes do take place. So called mutations occur when DNA subunits are replaced with other subunits (ATTCGG changes to ATTAGG), extra subunits are added (ATTCCCCGG) or subunits are lost (ATTGG). This can alter the function of proteins by changing the sequence of amino acids.
DNA and Evolution
These changes in DNA sequence provides variation in function, which is utilized by Natural selection to select and preserve those variations best suited to the environment.
Similarities and differences in DNA can be compared within species and between species (the sequence of subunits in DNA can be read).
Imagine Joe, Bob and Simon are at the blue sweet shop and each buys 5 blue sweets. Joe continues to buy blue sweets while Bob and Simon visit the red sweet shop and buy 5 red sweets each. Then Simon visits the yellow sweet shop and buys 5 yellow sweets. At the end of the shopping trip Joe has 15 blue sweets; Bob has 5 blue and 10 red sweets; Simon has 5 blue, 5 red and 5 yellow sweets. The only colour sweets they all share is blue; therefore, they must have started in the blue sweet shop. Similarly, if DNA is compared in humans from Africa, Europe and Asia, all individuals share some of the variations found in the African population; therefore, all humans originated in Africa.
If DNA from different species is compared, those species with a more recent common ancestor have lots of identical sequences while distantly related species have lots of differences. For example, we share 99% of our DNA with chimpanzees but only 50% with bananas; we are genetically more like chimps than bananas!
See Nature 421 395-453
Although the double helix structure of DNA allows for remarkably faithful and accurate replication, mistakes do take place. So called mutations occur when DNA subunits are replaced with other subunits (ATTCGG changes to ATTAGG), extra subunits are added (ATTCCCCGG) or subunits are lost (ATTGG). This can alter the function of proteins by changing the sequence of amino acids.
DNA and Evolution
These changes in DNA sequence provides variation in function, which is utilized by Natural selection to select and preserve those variations best suited to the environment.
Similarities and differences in DNA can be compared within species and between species (the sequence of subunits in DNA can be read).
Imagine Joe, Bob and Simon are at the blue sweet shop and each buys 5 blue sweets. Joe continues to buy blue sweets while Bob and Simon visit the red sweet shop and buy 5 red sweets each. Then Simon visits the yellow sweet shop and buys 5 yellow sweets. At the end of the shopping trip Joe has 15 blue sweets; Bob has 5 blue and 10 red sweets; Simon has 5 blue, 5 red and 5 yellow sweets. The only colour sweets they all share is blue; therefore, they must have started in the blue sweet shop. Similarly, if DNA is compared in humans from Africa, Europe and Asia, all individuals share some of the variations found in the African population; therefore, all humans originated in Africa.
If DNA from different species is compared, those species with a more recent common ancestor have lots of identical sequences while distantly related species have lots of differences. For example, we share 99% of our DNA with chimpanzees but only 50% with bananas; we are genetically more like chimps than bananas!
See Nature 421 395-453
Monday, 9 September 2013
Autobiography - the structure and function of DNA (part 2)
Structure of DNA
"....It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material."
Watson and Crick, 1953
Watson and Crick proposed that DNA forms a double helix: two separate DNA strands, each consisting of a row of subunits (A, T, G, C) attached to a ribbon-like backbone, are wound around each other. Within the double helix the subunits on one strand face and bind subunits on the other strand; only A binds to T and G binds to C.
ATCG
TAGC
Therefore, DNA is replicated by unzipping the double helix and each separated strand forms a template to allow individual subunits to bind their partner; thus generating two DNA molecules from the original molecule.
ATCG ATCG ATCG
TAGC TAGC
TAGC TAGC
ATCG
DNA encodes proteins
Proteins provide the structure of every cell in your body and carry out each function needed within the cell to keep you alive. DNA initiates and controls life by controlling which proteins are manufactured in the cell. Each protein is made from a gene, which is a specific sequence of DNA subunits.
DNA is said to express proteins: three subunits of DNA code for one amino acid (amino acids are the subunits of proteins) and it is the sequence of amino acids that determines the function of proteins.
The sequence of DNA is converted into proteins via RNA: DNA is unzipped but only one strand is a template to bind new subunits (A, C, G and U (instead of T)). A short sequence of these new subunits (called RNA) corresponding to a gene is then released from the strand of DNA.
GTCCTA GTCCTA GTCCTA
CAGGAT CAGGAU CAGGAU
RNA then encounters ribosomes, which mediate the interaction between RNA and amino acids.
CAGGAU CAGGAU
Q D QD...
Amino acids are sequentially added according to the sequence of RNA and therefore DNA. The resulting protein is released into the cell.
See Nature 421 395-453
"....It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material."
Watson and Crick, 1953
Watson and Crick proposed that DNA forms a double helix: two separate DNA strands, each consisting of a row of subunits (A, T, G, C) attached to a ribbon-like backbone, are wound around each other. Within the double helix the subunits on one strand face and bind subunits on the other strand; only A binds to T and G binds to C.
ATCG
TAGC
Therefore, DNA is replicated by unzipping the double helix and each separated strand forms a template to allow individual subunits to bind their partner; thus generating two DNA molecules from the original molecule.
ATCG ATCG ATCG
TAGC TAGC
TAGC TAGC
ATCG
DNA encodes proteins
Proteins provide the structure of every cell in your body and carry out each function needed within the cell to keep you alive. DNA initiates and controls life by controlling which proteins are manufactured in the cell. Each protein is made from a gene, which is a specific sequence of DNA subunits.
DNA is said to express proteins: three subunits of DNA code for one amino acid (amino acids are the subunits of proteins) and it is the sequence of amino acids that determines the function of proteins.
The sequence of DNA is converted into proteins via RNA: DNA is unzipped but only one strand is a template to bind new subunits (A, C, G and U (instead of T)). A short sequence of these new subunits (called RNA) corresponding to a gene is then released from the strand of DNA.
GTCCTA GTCCTA GTCCTA
CAGGAT CAGGAU CAGGAU
RNA then encounters ribosomes, which mediate the interaction between RNA and amino acids.
CAGGAU CAGGAU
Q D QD...
Amino acids are sequentially added according to the sequence of RNA and therefore DNA. The resulting protein is released into the cell.
See Nature 421 395-453
Sunday, 8 September 2013
Autobiography - the structure and function of DNA (part 1)
"It is the cause, it is the cause my soul..." - Shakespeare
Natural selection, the non-random selection of favourable traits in a limited environment, is responsible for the informational content of deoxyribonucleic acid; or DNA. The action of DNA was the cause that threw you (and indeed all life) into the world and determined your state of existence.
Therefore, to understand anything about who you are and where you came from it is crucial to understand DNA.
Discovering scientific knowledge
All scientific knowledge was once new knowledge:
Scientist's carry out experiments to isolate and identify causes. The data generated by their experiments either reveals the cause, the need to identify a deeper cause or uncovers an unexpected cause. This new knowledge forms a "brick", which other scientists examine and try to fit into the wall of knowledge already built. Sometimes the brick fits nicely, sometimes part of the wall has to be knocked down to accommodate the new brick while other times the bricks are discarded. In this way, the edifice of scientific knowledge is gradually built up.
Discovering DNA
In 1866 Gregor Mendel demonstrated that characteristics are passed from generation to generation in discreet units called genes. What these units were made of remained elusive; it was assumed proteins, the most abundant biological material, fulfilled this role.
In 1869 Fritz Miescher discovered an acidic substance in the nucleus of cells, which subsequently became known as DNA. In 1928, Griffith found that bacteria can share inherited material (genes) in a process called "transformation". In 1944 these findings were brought together when Avery, MacLeod and McCarty showed that DNA was the material that was responsible for transformation. This demonstrated that DNA forms units of inheritance.
How does DNA carry the information needed to build living things and how does it replicate itself so it is passed from generation to generation? Rosalind Franklin and Raymond Gosling generated an X-Ray diffraction pattern of DNA in 1952, which Watson and Crick used in 1953 to elucidate the structure of DNA. Remarkably, their proposal suggested answers to both questions.
See Nature 421 395-453
Natural selection, the non-random selection of favourable traits in a limited environment, is responsible for the informational content of deoxyribonucleic acid; or DNA. The action of DNA was the cause that threw you (and indeed all life) into the world and determined your state of existence.
Therefore, to understand anything about who you are and where you came from it is crucial to understand DNA.
Discovering scientific knowledge
All scientific knowledge was once new knowledge:
Scientist's carry out experiments to isolate and identify causes. The data generated by their experiments either reveals the cause, the need to identify a deeper cause or uncovers an unexpected cause. This new knowledge forms a "brick", which other scientists examine and try to fit into the wall of knowledge already built. Sometimes the brick fits nicely, sometimes part of the wall has to be knocked down to accommodate the new brick while other times the bricks are discarded. In this way, the edifice of scientific knowledge is gradually built up.
Discovering DNA
In 1866 Gregor Mendel demonstrated that characteristics are passed from generation to generation in discreet units called genes. What these units were made of remained elusive; it was assumed proteins, the most abundant biological material, fulfilled this role.
In 1869 Fritz Miescher discovered an acidic substance in the nucleus of cells, which subsequently became known as DNA. In 1928, Griffith found that bacteria can share inherited material (genes) in a process called "transformation". In 1944 these findings were brought together when Avery, MacLeod and McCarty showed that DNA was the material that was responsible for transformation. This demonstrated that DNA forms units of inheritance.
How does DNA carry the information needed to build living things and how does it replicate itself so it is passed from generation to generation? Rosalind Franklin and Raymond Gosling generated an X-Ray diffraction pattern of DNA in 1952, which Watson and Crick used in 1953 to elucidate the structure of DNA. Remarkably, their proposal suggested answers to both questions.
See Nature 421 395-453
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