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Lana
CLINICAL IMPORTANCE OF SUGARS IN BLOOD GROUP A,B,AB & O
~8.5 mins read
INTRODUCTION
In order to discuss the chemical importance of sugars in blood group A,BO &AB. It is important to first understand all about blood.
BLOOD
-Blood is a type of complicated and living tissue which holds numerous proteins and cell types. It is a connective tissue. Blood is important in our bodies due to its functions: defend, regulate, and transport.
Structure
carbohydrate chemistry is of great importance for the most commonly considered blood classification, the AB0 blood types. The blood types are named after antigens that are found on the surface of the red blood cells, and these antigens are simple chains of sugars.
Human blood groups depends on the functioning of glycosyltransferases, enzymes that catalyze the formation of glycosidic bond between monosaccharides. Specific oligosaccharide antigens attach to the proteins and lipids on the surface of erythrocytes. Those attached to proteins have a serine or threonine residue or ceramide lipid intermediate. The most basic oligosaccharide attached is called the O antigen (also referred to as the H antigen). This O antigen is the base oligosaccharide found in all three blood types AB, A, and B. The O antigen is of the form (—Lipid—Glucose—Galactose—N-acetylglucosamine—Galactose—Fucose). Blood type O only has the O antigen attached to the red blood cells. Blood type A is formed through the addition of the A antigen, which has N-acetylgalactosamine (GalNAc) glycosidically bonded to the O antigen. Similarly for blood type B, the B antigen has an additional galactose forming a glycosidic bond to the O antigen. In both the A and B blood types, the new antigen forms an α-1,3 linkage to the outermost galactose component of the O antigen through the help of glycosyltransferases. GalNAc transferase adds the extra N-acetylgalactosamine for the A antigen while Gal transferase adds the extra galactose for the B antigen. Genes in a person’s DNA code for the specific glycosyltransferases to allow for the addition of antigens A and/or B to the O antigen. If a person’s genes do not allow for the coding of type A or B transferase, then that person will have type O blood. The genes that code for GalNAc and Gal transferases are exact, but for three amino acids. This strong similarity between the two enzymes shows they are related through divergent evolution.
Functionality
The importance of glycosyltransferases is most prominent when a person needs a blood transfusion. Type O blood can be given to anyone because everyone has the ability to recognize the O antigen. However, a person with type A or type O blood cannot recognize the B antigen while another with type B or O blood cannot recognize the A antigen. Antibodies against the B and A antigens are also present in the serum of one’s blood for those who lack the B and A antigens, respectively. Therefore, if a person were transfused with the wrong type of blood, one’s immune system will see the antigen as foreign, therefore attacking those transfused red blood cells. It is because of this process that people with type AB blood can accept transfusions of any blood type, since they have all three antigens already present in their bodies. It should be noted that in reality, transfusions are complicated by the Rhesus factor.
Clinical importance:
1.Blood transfusion
2.Antibodies & antigens.
3.Susceptibility to disease: numerous associations have been made between a particular ABO phenotype and susceptibility to disease e.g. ABO phenotype has been linked with stomach ulcers ( common in group O individuals), gastric cancer (common in group A individuals).
4.Blood clotting: individuals with blood type O tend to have lower levels of the von Willebrand Factor (Vwf), which is a protein involved in blood clotting.
5.Proteins & Blood Types
· We can categorize our blood types into 4 groups: A, B, AB, & O
These four groups are considered to be the four phenotypes that one may posses. These four phenotypes can produce six different genotypes that each person can be: AA, AO, BB, BO, AB, and OO.
Carbohydrate Antigens on the Surface of Red Blood Cells
The types of oligosaccharides present on the surface of the red blood cells determine a person's blood type: if only the 0-type antigen is present, the blood type is 0, if only the antigen A or B is found, the blood is type A or B, respectively, and if both A and B antigens are present, the blood type is AB [1]. The A and B antigens differ only in a sidechain on the terminal sugar.
Blood type O has no antigens and thus have both A and B antibodies in its system. In this regard, blood type O may be the universal donor and blood type AB is the universal recipient.
· We can also look at the property of Rh protein whether it's absence or presence in our blood.
- If a blood type has Rh protein, then it is positive.
- If a blood type does not have Rh protein, then it is negative.
- For example, blood type "B negative" means that the person has type B without Rh protein on the surface of the red blood cells.
The RH factor is more important if the mother is to have a second child. This is because if the mother is RH - and her first child is RH + (has present of RH protein), the mother will produce antibodies (specific immunogenic proteins) for the RH protein. This will not affect the first child since the mother will only produce this antibody after the child is born. However, if the mother is to have a second child with an RH+ trait as well, the antibodies in the mother will cross the placenta and attack the child. This is because the antibodies for the RH protein are specific proteins called memory cells that are small enough to pass the placenta. This will result in a miscarriage.
One way around this is to give the mother Rhogam after birth. This is a synthetic protein antibody that will destroy the left over fetal cells before it has a chance to interact with the mother's immune system. This inhibit protein antibody production towards the RH factor in the mother and will allow subsequent RH+ children to be born from that mother.
Mixing Different Blood Types
Our body generates antigens or antibodies to protect us from the unfamiliar molecules. They will then recognize this difference and clash with the molecules to get rid of them.
· For blood transfusion, it is very important to make sure that both the recipient and the donor match in blood type.
- If surface molecules from the donor blood cells signals any difference than the recipient's, then the antibodies from the recipient’s blood will consider it as foreign.
- The immune response will take place if there is a difference in blood type, which results in blood clots in the vessels.
Universal Donors and Universal Recipients
· Blood type O is the universal donors due to its versatility of having no molecules on the red blood cell surfaces, which will not trigger any immune response. Therefore type O blood can be donated to any of the other four blood types earning its name.
· Blood type AB is the universal recipients due to its lack of antibodies that recognize type A or B surface molecules. AB can receive blood from any of the other four blood types earning its name as the universal receiver. AB however also tends to be the most rare blood type out of the four.
AB+ is the is the true universal receiver able to receive all types of blood regardless of type and Rh antigen.
However O- is only compatible with itself but able to donate to everyone.
The exception to these rules are people with the hh antigen system also called the Bombay blood type. These individuals cannot express the H antigen which is present in group O. They cannot make A antigen or B antigen since they are made from the H antigen. Therefore the people who have this blood type can donate to any other member of any blood type but can only receive blood from other Bombay blood type individuals. However this blood type is extremely rare occurring in only .0004% of the population. Therefore people with this blood type are at a great risk in finding compatible blood for a blood transfusion.
Rhesus Antigen
Not only do the different blood types have to be considered due to the existence of antigens but the rhesus blood group system is secondly important after the ABO system of blood type antigens. The most important antigen from the five main rhesus antigens is RhD since it is the most immunogenic. It is common for RhD negative people to have no anti-RhD IgG or IgM antibodies. The Rhesus antigen is usually depicted by a plus or a negative after the type of blood type. Rh positive is more prevalent than Rh negative blood types. Especially in East Asia the percentage of Rh negative people are extremely rare. Since people with Rh negative blood type cannot receive blood from Rh positive special care must be taken when receiving blood transfusions.
Testing for Rhesus Antigen
Test can be carried out to determine whether one's blood contains the Rh antigen. Since Rh factors are antigens there are corresponding antibodies that can be used to bind. Rh antibodies are commonly used to bind to such antigens in the blood. The structure of the antibody is oriented in a fashion so that there are two main chains, a heavy chain and light chain. The two heavy chains are located on the inner side of the antibody while the light chains are located on the outer. The domains are exactly the same pertaining to all antibodies except for the last domain the the N terminus of both the heavy and light chain located on each side of the antibody. It is the variable domain that is different from antibody to antibody and contains differential amino acid sequences with their constituent residues that provide complementarity in the binding site to the specific substrate. If Rh antibodies are mixed with ones blood and aggregation occurs, then the person would be Rh positive, if no aggregation occurs, then the person is Rh negative. Aggregation occurs due to the antibody-substrate complex that forms when the Rh antigen locks into the binding site of the antibody.
Red Blood Cells Vs Blood Plasma
Like red blood cell compatibility recipients can receive blood plasma from the same blood type. However unlike with red blood cells the plasma has a converse compatibility. Blood type O can receive plasma from every other blood type while blood type AB can donate blood plasma to any blood type.
Blood Types Genetics
· Blood types A & B co-dominate
· Blood type O is recessive
· We can see the patterns of the possible combination of alleles versus the blood types:
AB = blood type AB
BB = blood type B
AA = blood type A
OO = blood type O
BO = blood type B
AO = blood type A
Blood type A can receive both type A and type O blood. Similarly, blood type B can receive both type B and type O blood. However, blood type AB can receive type A and type B blood, as well as, type O blood, making them the universal recipients. Blood type O is rare in that it can only receive type O blood, but can donate to any of the other three blood types, making them the universal donors.
REFERENCES
1.Nelson, David L. Principles of Biochemistry, 4th ed. W. H. Freeman, 2004. .http://www.ncbi.nlm.nih.gov/books/bv.fcgi?indexed=google&rid=mcb.section.4816
2.Molecular Cell Biology, Lodish H., Berk A., Zipursky S. L., et al., W. H. Freeman, New York, 2000. ISBN: 978-0716737063
3.Essential Guide to Blood Groups, Geoff Daniels, Imelda Bromilow, John Wiley & Son, Hoboken, 2014. DOI: 10.1002/9781118688915
4. Reid ME and Lomas-Francis C.The blood group antigen facts book. Second ed. 2004, New York: Elsevier Academic press.
In order to discuss the chemical importance of sugars in blood group A,BO &AB. It is important to first understand all about blood.
BLOOD
-Blood is a type of complicated and living tissue which holds numerous proteins and cell types. It is a connective tissue. Blood is important in our bodies due to its functions: defend, regulate, and transport.
Structure
carbohydrate chemistry is of great importance for the most commonly considered blood classification, the AB0 blood types. The blood types are named after antigens that are found on the surface of the red blood cells, and these antigens are simple chains of sugars.
Human blood groups depends on the functioning of glycosyltransferases, enzymes that catalyze the formation of glycosidic bond between monosaccharides. Specific oligosaccharide antigens attach to the proteins and lipids on the surface of erythrocytes. Those attached to proteins have a serine or threonine residue or ceramide lipid intermediate. The most basic oligosaccharide attached is called the O antigen (also referred to as the H antigen). This O antigen is the base oligosaccharide found in all three blood types AB, A, and B. The O antigen is of the form (—Lipid—Glucose—Galactose—N-acetylglucosamine—Galactose—Fucose). Blood type O only has the O antigen attached to the red blood cells. Blood type A is formed through the addition of the A antigen, which has N-acetylgalactosamine (GalNAc) glycosidically bonded to the O antigen. Similarly for blood type B, the B antigen has an additional galactose forming a glycosidic bond to the O antigen. In both the A and B blood types, the new antigen forms an α-1,3 linkage to the outermost galactose component of the O antigen through the help of glycosyltransferases. GalNAc transferase adds the extra N-acetylgalactosamine for the A antigen while Gal transferase adds the extra galactose for the B antigen. Genes in a person’s DNA code for the specific glycosyltransferases to allow for the addition of antigens A and/or B to the O antigen. If a person’s genes do not allow for the coding of type A or B transferase, then that person will have type O blood. The genes that code for GalNAc and Gal transferases are exact, but for three amino acids. This strong similarity between the two enzymes shows they are related through divergent evolution.
Functionality
The importance of glycosyltransferases is most prominent when a person needs a blood transfusion. Type O blood can be given to anyone because everyone has the ability to recognize the O antigen. However, a person with type A or type O blood cannot recognize the B antigen while another with type B or O blood cannot recognize the A antigen. Antibodies against the B and A antigens are also present in the serum of one’s blood for those who lack the B and A antigens, respectively. Therefore, if a person were transfused with the wrong type of blood, one’s immune system will see the antigen as foreign, therefore attacking those transfused red blood cells. It is because of this process that people with type AB blood can accept transfusions of any blood type, since they have all three antigens already present in their bodies. It should be noted that in reality, transfusions are complicated by the Rhesus factor.
Clinical importance:
1.Blood transfusion
2.Antibodies & antigens.
3.Susceptibility to disease: numerous associations have been made between a particular ABO phenotype and susceptibility to disease e.g. ABO phenotype has been linked with stomach ulcers ( common in group O individuals), gastric cancer (common in group A individuals).
4.Blood clotting: individuals with blood type O tend to have lower levels of the von Willebrand Factor (Vwf), which is a protein involved in blood clotting.
5.Proteins & Blood Types
· We can categorize our blood types into 4 groups: A, B, AB, & O
These four groups are considered to be the four phenotypes that one may posses. These four phenotypes can produce six different genotypes that each person can be: AA, AO, BB, BO, AB, and OO.
Carbohydrate Antigens on the Surface of Red Blood Cells
The types of oligosaccharides present on the surface of the red blood cells determine a person's blood type: if only the 0-type antigen is present, the blood type is 0, if only the antigen A or B is found, the blood is type A or B, respectively, and if both A and B antigens are present, the blood type is AB [1]. The A and B antigens differ only in a sidechain on the terminal sugar.
Blood type O has no antigens and thus have both A and B antibodies in its system. In this regard, blood type O may be the universal donor and blood type AB is the universal recipient.
· We can also look at the property of Rh protein whether it's absence or presence in our blood.
- If a blood type has Rh protein, then it is positive.
- If a blood type does not have Rh protein, then it is negative.
- For example, blood type "B negative" means that the person has type B without Rh protein on the surface of the red blood cells.
The RH factor is more important if the mother is to have a second child. This is because if the mother is RH - and her first child is RH + (has present of RH protein), the mother will produce antibodies (specific immunogenic proteins) for the RH protein. This will not affect the first child since the mother will only produce this antibody after the child is born. However, if the mother is to have a second child with an RH+ trait as well, the antibodies in the mother will cross the placenta and attack the child. This is because the antibodies for the RH protein are specific proteins called memory cells that are small enough to pass the placenta. This will result in a miscarriage.
One way around this is to give the mother Rhogam after birth. This is a synthetic protein antibody that will destroy the left over fetal cells before it has a chance to interact with the mother's immune system. This inhibit protein antibody production towards the RH factor in the mother and will allow subsequent RH+ children to be born from that mother.
Mixing Different Blood Types
Our body generates antigens or antibodies to protect us from the unfamiliar molecules. They will then recognize this difference and clash with the molecules to get rid of them.
· For blood transfusion, it is very important to make sure that both the recipient and the donor match in blood type.
- If surface molecules from the donor blood cells signals any difference than the recipient's, then the antibodies from the recipient’s blood will consider it as foreign.
- The immune response will take place if there is a difference in blood type, which results in blood clots in the vessels.
Universal Donors and Universal Recipients
· Blood type O is the universal donors due to its versatility of having no molecules on the red blood cell surfaces, which will not trigger any immune response. Therefore type O blood can be donated to any of the other four blood types earning its name.
· Blood type AB is the universal recipients due to its lack of antibodies that recognize type A or B surface molecules. AB can receive blood from any of the other four blood types earning its name as the universal receiver. AB however also tends to be the most rare blood type out of the four.
AB+ is the is the true universal receiver able to receive all types of blood regardless of type and Rh antigen.
However O- is only compatible with itself but able to donate to everyone.
The exception to these rules are people with the hh antigen system also called the Bombay blood type. These individuals cannot express the H antigen which is present in group O. They cannot make A antigen or B antigen since they are made from the H antigen. Therefore the people who have this blood type can donate to any other member of any blood type but can only receive blood from other Bombay blood type individuals. However this blood type is extremely rare occurring in only .0004% of the population. Therefore people with this blood type are at a great risk in finding compatible blood for a blood transfusion.
Rhesus Antigen
Not only do the different blood types have to be considered due to the existence of antigens but the rhesus blood group system is secondly important after the ABO system of blood type antigens. The most important antigen from the five main rhesus antigens is RhD since it is the most immunogenic. It is common for RhD negative people to have no anti-RhD IgG or IgM antibodies. The Rhesus antigen is usually depicted by a plus or a negative after the type of blood type. Rh positive is more prevalent than Rh negative blood types. Especially in East Asia the percentage of Rh negative people are extremely rare. Since people with Rh negative blood type cannot receive blood from Rh positive special care must be taken when receiving blood transfusions.
Testing for Rhesus Antigen
Test can be carried out to determine whether one's blood contains the Rh antigen. Since Rh factors are antigens there are corresponding antibodies that can be used to bind. Rh antibodies are commonly used to bind to such antigens in the blood. The structure of the antibody is oriented in a fashion so that there are two main chains, a heavy chain and light chain. The two heavy chains are located on the inner side of the antibody while the light chains are located on the outer. The domains are exactly the same pertaining to all antibodies except for the last domain the the N terminus of both the heavy and light chain located on each side of the antibody. It is the variable domain that is different from antibody to antibody and contains differential amino acid sequences with their constituent residues that provide complementarity in the binding site to the specific substrate. If Rh antibodies are mixed with ones blood and aggregation occurs, then the person would be Rh positive, if no aggregation occurs, then the person is Rh negative. Aggregation occurs due to the antibody-substrate complex that forms when the Rh antigen locks into the binding site of the antibody.
Red Blood Cells Vs Blood Plasma
Like red blood cell compatibility recipients can receive blood plasma from the same blood type. However unlike with red blood cells the plasma has a converse compatibility. Blood type O can receive plasma from every other blood type while blood type AB can donate blood plasma to any blood type.
Blood Types Genetics
· Blood types A & B co-dominate
· Blood type O is recessive
· We can see the patterns of the possible combination of alleles versus the blood types:
AB = blood type AB
BB = blood type B
AA = blood type A
OO = blood type O
BO = blood type B
AO = blood type A
Blood type A can receive both type A and type O blood. Similarly, blood type B can receive both type B and type O blood. However, blood type AB can receive type A and type B blood, as well as, type O blood, making them the universal recipients. Blood type O is rare in that it can only receive type O blood, but can donate to any of the other three blood types, making them the universal donors.
REFERENCES
1.Nelson, David L. Principles of Biochemistry, 4th ed. W. H. Freeman, 2004. .http://www.ncbi.nlm.nih.gov/books/bv.fcgi?indexed=google&rid=mcb.section.4816
2.Molecular Cell Biology, Lodish H., Berk A., Zipursky S. L., et al., W. H. Freeman, New York, 2000. ISBN: 978-0716737063
3.Essential Guide to Blood Groups, Geoff Daniels, Imelda Bromilow, John Wiley & Son, Hoboken, 2014. DOI: 10.1002/9781118688915
4. Reid ME and Lomas-Francis C.The blood group antigen facts book. Second ed. 2004, New York: Elsevier Academic press.
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Lana
THE INFLUENCES OF GENES ON BEHAVIOUR
~4.1 mins read
INTRODUCTION
Scientists have studied twins for many years to understand how genes and environments influence differences among individuals, spanning conditions such as cancer and mental health to characteristics such as intelligence and political beliefs.
Although the twin method is well-established, findings from twin studies are often controversial. Critics of twin research question the value of establishing that characteristics, such as health behaviours, have a strong genetic basis. A primary concern is that these types of findings will result in complacency or fatalism, effectively undermining motivation to change lifestyle. But there is very little evidence to support these fears.
Genetic influence on human characteristics is often misinterpreted. It is wrongly assumed that a behaviour that has strong genetic influence (highly heritable) must be biologically hardwired. However, genes are not destiny. Genes are often dependent on environmental exposure, such that genes can have a stronger effect, or no effect, depending on the environment.
For example, people with a genetic predisposition to lung cancer are unlikely to develop the disease unless they smoke. The same is true of behaviour. Behaviour is only elicited in response to environmental cues. Establishing that a behaviour has an important genetic basis does not imply that this behaviour cannot be changed through environmental means.
The influence of genes on behavior has been well established in the scientific community. To a large extent, who we are and how we behave is a result of our genetic makeup. While genes do not determine behavior, they play a huge role in what we do and why we do it.
Behavioral genetics studies heritability of behavioral traits, and it overlaps with genetics, psychology, and ethology (the scientific study of human and animal behavior). Genetics plays a large role in when and how learning, growing, and development occur. For example, although environment has an effect on the walking behavior of infants and toddlers, children are unable to walk at all before an age that is predetermined by their genome. However, while the genetic makeup of a child determines the age range for when he or she will begin walking, environmental influences determine how early or late within that range the event will actually occur.
The field was originally focused on testing whether genetic influences were important in human behavior (e.g., do genes influence human behavior). It has evolved to address more complex questions such as: how important are genetic and/or environmental influences on various human behavioral traits; to what extent do the same genetic and/or environmental influences impact the overlap between human behavioral traits; how do genetic and/or environmental influences on behavior change across development; and what environmental factors moderate the importance of genetic effects on human behavior (gene-environment interaction). ‪
Most recently, the field has moved into the area of statistical genetics, with many behavioral geneticists also involved in efforts to identify the specific genes involved in human behavior, and to understand how the effects associated with these genes changes across time, and in conjunction with the environment.
(Encyclopedia Britannica, Behavior Genetics by Robert Plomin, 4-11-2011)
GENETICS
Genetics is the study of heredity. Heredity is a biological process where a parent passes certain genes onto their children or offspring. Every child inherits genes from both of their biological parents and these genes in turn express specific traits. Some of these traits may be physical for example hair and eye color and skin color etc. On the other hand some genes may also carry the risk of certain diseases and disorders that may pass on from parents to their offspring.
Previously it had been difficult to link particular chromosome with psychiatric illness. However in a number of studies over years such an association has been made. E.g., schizophrenia, mood disorders, neuropsychiatric disorders, personality disorders, alcoholism, and personality traits.
Specific chromosomes have been associated with other disorders with behavior symptoms. Example:
1. Schizophrenia has been associated with markers on chromosome 1, 6, 7, 8, 13, 21 and 22.
2. Bipolar disorder and major depressive disorder have been associated with markers on chromosome 3, particularly 3p21.1.
TYPES OF STUDIES USED IN GENETIC RESEARCH
· Twin studies
a. Used in genetic research to study the correlation between genetic inheritance and behaviour due to the common genetics shared by twins.
b. Monozygotic twins (MZT) identical - share 100% genetic material.
c. Dizygotic twins (DZT) fraternal - share 50% genetic material.
d. It is usually further explored, by studying the twins either separated or together to make a correlation of their behaviour.
· Adoption studies
a. Allow researchers to study the comparison between genetic and environmental influence on behaviour.
b. Adopted children share no genes with their adoptive parents but 50% of genes with their biological parents.
· Family studies
a. Study behaviour between family members who have similar genetics to different degrees.
· Outline intelligence
a. Intelligence is an aspect of behaviour that has been studied in relation to genetics.
b. It was questioned whether intelligence was attributed to genetic or environmental factors. Intelligence difficult to define
c. IQ tests have been developed by a French person called Binet to measure of intelligence and are used in much psychological research.
CONCLUSION
Identifying a chromosomal abnormality in a patient with mental disorder is of profound importance to the individual and their family. Diagnosis of a chromosomal abnormality can alter medical management and affect prognosis with respect to known associated conditions, and has important genetic counseling implications. In addition, receiving a genetic diagnosis may relieve parents of guilt or inappropriate blame for causing behavioral manifestations of the condition.
REFERENCES
1. Boundless. “The Influence of Genes on Behavior.” Boundless Psychology. Boundless, 26 May. 2016.
2. Dick, Danielle; Rose, Richard (2002). "Behavior Genetics: What's New? What's Next". Current Directions in Psychological Science (11): 70–74.
3. Encyclopedia Britannica, Behavior Genetics by Robert Plomin, 4-11-2011
4. http://theconversation.com/why-it-is-useful-to-understand-the-role-of-genetics-in-behaviour-67502
5. Wikipedia, Human Behavior Genetics
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