ABO blood group

Age sex and population variation as genetic marker-ABO, Rh blood groups, HLA Hp ,Transferring, Gm, Blood enzymes. physiological characteristics-Hb level, body fat, pulse rate, respiratory functions and sensory perceptions in different cultural and socio economic groups.

When a sample of blood taken and kept in a tube for a considerable time, the red cells settle at the bottom of the tube leaving the white cells to form a thin layer above these. On the top lies the plasma.

The plasma is a coagulable fluid. It contains a variety of substances like fibrinogen,albumin,globin,amino acid,sugar,fat. When the coagulating and coagulable elements are removed from the plasma,a clear fluid is obtained. This is serum.

There are three kinds of blood corpuscles: rbc(erythrocytes);wbc(lekucytes);blood platelets.

The genetic markers in red blood cells can conveniently be discussed under three major heads:a. red cells antigens:blood group polymorphisms;b. Hemoglobins; c. enzymes.

a. red cell antigens:blood group polymorphisms.

The ABO system

When the red cells from the blood of one individual are introduced into the serum of another,the cells may clump- a reaction called Agglutination.

The four types can be explained by the presence or absence of either or both of two substances (the a and b antigens) on the cells. Transfusing A type blood in to b group patient could produce a severe reaction. The reason why transfusion of blood of the wrong type produce serious and sometimes fatal results is that human blood contains antibodies as well as antigens. The red cells of the donar are agglutinated if the recipient has antibodies to their antigens. Blood owners of type o have red cells that are not normally clumped and destroyed by anyones else serum,so that the blood of group o persons are called universal donar.

To study the genetic bases of the traits we begin by analysing the phenotype of the trait.

Mating between type A,type B,type O individuals yielded more children of types A and B than of O. this indicated alleles controlling A and B phenotypes are dominant over O alleles. Since children of parent of type A and Parent of type B showed AB phenotypes, it was assumed that both A and B alleles are dominant.

Blood group B-37% in Mangloids,25% in Egypt,22% in Ukraine,15% in Europe,2% in American population.

Blood group A-45% in england,blood group O-96% in north america.

In the world statistics,blood group O IS common followed by blood group blood group A which is trailed by blood group B.

Rh system

A serum may be obtained from a rabbit when the blood of a rhesus monkey is injected into the former. That serum agglutinates blood of certain human individual and not of others. This new agglutinable factor is called the Rh Factor, the Rh symbol being obviously derived from the word rhesus. Those person who possess this factor are called Rh positive and those who lack it are called Rh negative. This Rh system is independent of the ABO systems.

At first it was thought that Rh factor was inherited as a simple Mendelian pair,Rh and rh,Rh being dominant to rh, and that there were three genotypes like RhRh,Rhrh,rhrh. But now it is known that there are three Rh factors like Rh,rh and rh of which the original Rh is more powerful and is clinically more significant.

Among the Mongoloids Rh negative is very rare. A severe hemolytic disease known as erthroblastosis fetalis, condition apparent at birth may occur because of Rh incompatability.

Genetic markers in Plasma(Serum protein)

Both Plasma and serum, the yellow fluid portion of blood contain several soluble proteins. These proteins can easily be separated from each other by electrophoresis.

Hp(Haptoglobin)

haptoglobin is alpha-globin. It combines with haemoglobin in the plasma. But by electrophoresis it can easily be identified. There are essentially three different types of haptoglobin, such as Hp-1-1, Hp 1-2 and Hp 2-2, in which two genes namely Hp1 and Hp2 are involved. Hp 1-1 and Hp 2-2 are homozygous while Hp 1-2 is heterozygous for Hp1 and Hp2. These two are co dominant autosomal alleles. The two alleles follow mendelian principle of inheritance. In african population many persons are met with whose serum haptoglobin is absent. They are called ahaptoglobinemic(HpO).

Among some population of central and west africa as well as of central and south america Hp1 gene occurs in very high frequency. The worldwide distribution of this gene indicates that its frequency rises from india to north north america through siberia on one hand and to western and northern europe on other.

Transferring(Tf): transferrins are part of beta globins. They have chemical properties of binding iron. The important functions of these proteins is to transport oxidised iron to and from the bone marrow(where Hb is synthesized) and other tissues.

Several molecular varieties of transferrin have been identified. Each one is non dominant autosomal alleles located in the same locus. The most common is the C type(TfC) in all populations of the world.

Glucose-6-phosphate-dehydrogenase(G6PD).

G6PD is a red cell enzyme, which normally metabolizes glucose in the red blood cells. Some persons are deficient of this enzyme called G6PD deficiency. Such persons when treated with certain antimalerial drugs, especially primaquine, develop hemolytic anemia. Individuals with this deficiency are met with in africa, southeast asia, indonesian archipelago, burma, india.

Again, some persons when eat fava beans or even if they breathe the pollen, they develop this type of anemia. This disease is called favism. These individuals are also deficient of G6PD.

The distribution of G6PD deficiency can be correlated with that of falciparum malaria. It is noted that individuals with G6PD deficiency are better protected against malaria infection.

G6PD deficiency is inherited. It is a X linked trait. Homozygous females are clearly deficient. But heterozygous females show various degrees of deficiency or none at all. Therefore it appears to be incompletely dominant.

Hemoglobin.

Hemoglobins are ferroproteins composed of globin and haem. Globin constitutes the protein part made up of several common amino acids. Heme is a large organic molecule having an atom of iron. The function of hemoglobin is to carry oxygen from the lungs to the body tissue and also to remove carbon dioxide from the same.

The hemoglobin molecule of a normal adult human consist of four polypeptide chains,two identical alpha chains and two identical beta chains. Each alpha chains contain 141 amino acids, and each beta chains contains 146 amino acids. There are altogether 574 amino acids.

Various mutational event may affect a hemoglobin. The common hemoglobin varients or abnormal hemoglobins are: HbS(sickle cell anemia.),HbE,HbC,Thalassemia.

The hemoglobin lavel in a cell fluid is 35 gm per decilitre(gm/dl). It never rises above this level.

From the age of 20 years to 60 years the level of Hb among the males is maintained at 15.3 gm/dl. The females reach th e highest level of Hb, which is 13.5 gm/dl, by the age of 10-14. after the age of 14 boys improve their Hb level by attaining 15.3 gm/dl whereas females more or less remain stagnant due to menstrual losses.

Variation in Body fat.

When the child is attaining prepubescent height, 1.e., from 9 months to 8 years, the fat level shows negative velocity. This decrease in the fat level is due to the breakdown of fat by the growth hormone. While both boys and girls show reduction in the fat level till the age of 8 years, the decrease in girls is comparatively slow.

It is only at adolescence that a temporary halt in increasing fat level increases the fat level is seen among the boys and this loss of fat is gained back after 20.

pulse rate.

Pulse is the number of heart beat per minute. It is measured at the wrist,neck,temple,groin,behind the knees,or on top of the foot.

For resting heart rate:

newborn infants;100 to 160 beats per minute.

Children 1 to 10 years;70 to 120 beats per minute.

Children over 10 and adults;60 to 100 beats per minute.

Well trained atheletes; 40 to 60 beats per minute.

Variation in blood presssure.

The blood pumped by heart into blood vessels for its distribution to different parts of the body must leave the heart at some pressure because it has to overcome the resistance offered by frictional and other forces. The pressure at which blood leaves heart is called Systolic blood pressure(SBP) and the pressure at which it receive blood is diastolic blood pressure(DBP). A rise in the SBP indicate increases contraction and rise in DBP indicates decreased relaxation of the heart both being harmful if they cross optimal levels. The blood pressure during neonates first day averages 70/50. increase in bp during several months to 90/60. a pressure of 120/80 is considered an average for the adults,values as low as 115/70 is also considered normal. Following three groups on the variation of BP can be observed.

a)Hypertensive: SBP>169 mm hg

DBP>95 mm hg

b)boarderline cases:SBP.140-160 mm hg

DBP.90-95 mmhg

c)Normotensives:SBP<140 mm hg

DBP<90 mm hg

Variation in sense perception.

Among the various sensory mechanisms, the most throughly surveyed are ability to taste phenylthiocarbamide(PTC) and red and green color blindness. The ability to taste PTC IS AN autosomal polymorphic triat. Tasters with genotype TT,Tt have the ability to taste the substance while non tasters are homozygous for the recessive allele t.

red green color blindness is an X linked trait in which individuals fail to distinguish red and green from other colors.

Most of the studies related to PTC tasting have found sex differences in the trait; females are found to be more sensitive to the taste of PTC.

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