GENETICS:-

Mohsin Nawaz

GENETICS:-

Blood, Antigens And Antibodies,

Blood Groups

Blood:- The human blood is a fluid connective

tissues contacting two principal components.

1. Cells (red, white and platelets)2. Liquid (plasma) The plasma is composed of

clotting protein fibrinogen and serum

When the blood of one individual is mixed with the serum of the other person, then in certain cases clumping of red blood cells takes place.

The clumping of cells takes place due to the antigen-antibody reaction

Antibody An antibody is a molecule that is

synthesized by an animal in response to presence of foreign substances known as antigens.

The structure of antibody consists of two heavy chains (H-chains) and two light chains (H-chains).

The antibody has a constant and variable part

ABO Blood Types:-

Blood differs chemically from person to person

There are four types of ABO blood.

1. Group A phenotype = A/A or A/O genotype

2. Group B phenotype = B/B or B/O genotype

3. Group O phenotype = O/O genotype

4. Group AB phenotype = A/B genotype

Agglutination testAgglutinins` means antibodies. To

determine the blood group types of different persons

Clinical significant of ABO Blood Groups:

Persons who make antibodies against these antigens results in an agglutination reaction in which the donor red blood cells are clumped.

In this reaction, the anti-A antibody will agglutinate red blood cells of either blood type A or blood type AB, because both carry the A antigen.

When the blood cells agglutinate, many Clinical significant of ABO Blood Group is that transfusing of blood containing. A or B red antigens into blood vessels are blocked, and the recipient of the transfusing goes into shock and may die.

In compatibility in the other direction, in which the donor blood contains antibodies against the recipient’s red blood cells is usually acceptable because the donor’s antibodies are diluted. So rapidly that clumping is avoided .

The type compatible blood transfusions.

Bombay Phenotype . The allele h is found to be epistatic to the multiple

alleles at the A-B-O locus. Erythrocytes of persons having –hh genotype give no reaction with anti-A or anti-B sera (even though they possess I or I genes). In fact, they contain no antigen of this multiple allelic series.

Rh factor

Individual whose blood cells react with the Rh antibody are termed Rh+, those who do not react are Rh-.

Test for Rh incompatibility:-

A test for Rh incompatibility is done by placing a drop of Blood from the subject on a slide and introducing anti-Rh serum. Agglutination of red blood corpuscles indicate incompatibility, whereas an even distribution of RBCs indicate no reaction.

Erythroblast sis Fetalis:

Genetic Control of Rho Antigen: A and Rh+ blood group B and Rh- blood group

IAIA DD X IBIB dd (IAD) (IBd) IA IB Dd AB and Rh+ blood group

  IAD IAd IBD IBd

IAD IA IA DD A Rh+

IA IA Dd A Rh+

IA IB DD AB Rh+

IA IB Dd AB Rh+

IAd IA IA Dd A Rh+

IA IA dd A Rh-

IA IB Dd AB Rh+

IA IB dd AB Rh-

IBD

IA IB DD AB Rh+

IA IB Dd AB Rh+

IB IB DD B Rh+

IB IB Dd B Rh+

IBd

IA IB Dd AB Rh+

IA IB dd A Rh-

IB IB Dd B Rh+

IB IB dd B Rh-

F2 Phenotypic Ratio: 3: 1:3: 1: 6: 2