Rh Blood Group System

 Rh Blood Group System

            The Rh Blood group system is one of the clinically most important blood group systems. The term Rh in the name of this system refers to the Rhesus monkey. This blood group is determined by the Rh antigen present on the surface of the RBC. 

    The antigen was first discovered in Rhesus monkeys by Landsteiner in the 1930s.

Basis of Rh blood group system

            The Rh Blood group system is determined by up to 50 known antigens among which D, C, E, c, and e are the most significant. Rh blood group system is mainly controlled by the D gene.

The dominant gene D expresses D-antigen/Rh factor, while its alternative allele d inhibits the formation of Rh factor. The allele D is completely dominant over the allele d.

Rh Blood group types

    There are two types of blood groups in this system.

        1. Rh-positive: The person having a “D” antigen on the RBC membrane will have the Rh-positive blood group.

            2.  Rh negative: The person without “D” antigen on the RBC membrane will have the Rh negative blood group

Table 22.4  Rh-Blood group system
Blood group	Rh antigen	Genotypes	Anti-Rh-Antibody	Can receive blood from	Can donate blood to
Rh Positive	Present	DD or Dd	Not Produced	Rh Positive and Rh-Negative	Rh Positive
Rh-Negative	Absent	dd	Produced (if stimulated)	Rh-negative	Rh Positive and Rh-Negative

Maternal-Foetal Rh incompatibility – Erythroblastosis Foetalis

Erythroblastosis fetalis is a hemolytic disease of the newborn. In this disease, the red blood cells (erythrocytes) of the fetus are destroyed due to blood group incompatibility between the fetus and its mother. This incompatibility arises when the fetus inherits the Rh factor from the father that is absent in the mother.

Causes

    Rh factor inherits as a dominant trait. When a male with Rh-positive blood (having Rh antigen) marries a female with Rh-negative blood (without Rh antigen), the fetus will have the Rh-positive blood group. When fetal red blood cells with the Rh factor enter the mother’s bloodstream, the production of Rh antibodies occurs. These antibodies pass across the placenta into fetal blood and cause the destruction of the red blood cells of the fetus. The anemic fetus then starts to produce many immature erythroblasts. This is called erythroblastosis fetalis. This may lead to abortion or stillbirth

Also, learn about

Multiple Alleles

ABO Blood group system

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ABO BLOOD GROUP

 ABO BLOOD GROUP

    ABO blood group system was discovered in 1901 by Karl Landsteiner of the University of Vienna. Later he was awarded a Nobel Prize. ABO blood groups are found in all humans and in many primates such as apes, chimpanzees, baboons and gorillas.

Genetic Basis

    The ABO blood groups are controlled by Gene I located on the chromosome 9. Gene I has three allelic forms i.e. I^A , I^B and i. The I^A and I^B alleles each encode a glycosyltransferase that catalyzes the A and B antigen synthesis, respectively. The O or i allele encodes an inactive glycosyltransferase that leaves the ABO antigen precursor (the H antigen) unmodified. 

Blood type	Antigen on RBC	Allele for Antigen	Possible Genotypes	Dominance relation
A	A	IA	IA IA ,  IAi	IA Dominant to i
B	B	IB	IB IB , IBi	IB Dominant to i
AB	A & B	IA and IB	IA IB	IA and IB  Co-Dominant
O	None	I	ii	i is recessive

Blood group types

    A person’s blood group may be one of four types: A, B, AB, or O. These blood group types are due to the presence of antigen A and antigen B on the surface of RBC. A person having antigen a on the surface of RBC will have blood group A, having antigen B on the surface of RBC will have blood group B, and having both A and B antigens will have blood group AB. When no antigen is expressed (nor A or B), then the blood group is said to be the O blood group. 

Ability to produce Antibodies against antigen A and Antigen B

    The blood group is determined by antigens present on the surface of RBCs. The immune system can produce antibodies against the foreign antigens. In normal conditions, the body does not produce antibodies against the body's cells but can produce against any foreign agent that enters into the body.

Blood group A:     An individual with blood group A has antigen A on the RBC surface, therefore, it only produces Antibodies against antigen B. 

Blood group B:     A person having blood group B produces antibodies against the antigen A.

Blood group O:    A person having no antigen A or B on the surface of RBC (Blood group O) produces anti-A and anti-B antibodies.

Blood group AB:     Those who have AB blood group do not produce antibodies. 

Universal donor:

    Blood type O has no antigen therefore; a person with blood group O can donate the blood to all blood types.

Universal recipient: 

    A person with blood type AB does not produce anti-A and anti-B antibodies and, therefore can transfuse blood from all blood types.

Other blood group systems:  Besides the ABO blood group system there are also some other blood group systems i.e. Rh, MNS, P, Lutheran, Kell, Lewis, secretor, Duffy, Kidd, Diago, etc.

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Multiple Alleles

Rh blood group system

Rh Blood Group system

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 Multiple Allele

    An allele is the alternative form of a gene. When more than two forms of a gene exist on a single chromosome locus, the alleles are called multiple alleles.

Production of multiple alleles

    Multiple alleles are produced by gene mutation. A slight change in the nucleotide sequence of a gene results in the formation of alleles.

Number of multiple alleles

    The number of alleles controlling a character varies. The ABO blood group system is controlled by three alleles of gene I. Some genes may have as many as 300 alleles for a character. Multiple alleles exist in the individual of a population but individuals have only two of those alleles. This is because most organisms are diploid with two homologs of each chromosome. 

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ABO Blood group system

Rh blood group system

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An Introduction to the Respiratory System

Basic concepts 

Respiration, or breathing, is important for the homeostasis. 

What is ventilation?

Ventilation is simply the movement of air into and out of the lungs. ventilation is also called breathing. Breathing has two stages.

a. Breathing in or inhalation or inspiration

In this stage of breathing, air flows into the lungs.

a. Breathing out or exhalation or expiration

In this stage, the air flows out of the lungs. 

What is respiration?

Respiration is the diffusion of gases across plasma membranes. 

Types of respiration

There are two major types of respiration 

    

1. pulmonary respiration, or external respiration, 

It is the movement of gases between atmospheric air in the lungs and the blood. 

2. systemic respiration, or internal respiration

It is the movement of gases between the blood and the body’s cells.

The respiratory system

        The respiratory system consists of the structures used to exchange respiratory gases (oxygen and carbon dioxide) between air and blood. 

Division of the respiratory tract

The respiratory tract is separated into two regions:

A. The upper respiratory tract

The upper respiratory tract includes the structures from the nose to the larynx.

B. The lower respiratory tract

The lower respiratory tract includes the structures from trachea through the alveoli in the lungs. 

The upper and lower respiratory tract can be further subdivided based on their functions. 

a. The conducting zone 

It encompasses the structures from the nose to the smallest air tubes within the lungs. these are used for ventilation. 

b. The respiratory zone

it includes small air tubes (respiratory bronchioles) and the alveoli. Gas exchange occurs within the respiratory zone. 

Structures of the respiratory system 

a. External nose.

The external nose encloses the nasal cavity. It is the first and only external part of the respiratory system. 

b. Nasal cavity. 

    It is lined with the mucus membrane and cilia. It helps clean, warm, and humidify inspired air.

c. Pharynx. 

The pharynx is commonly called the throat. It serves as a common passageway for food and air.

d. Larynx. 

The larynx is also called the voice box. It is a rigid cartilaginous structure that helps keep the airway open. It also helps in sound production. 

e. Trachea. 

The trachea is commonly known as the windpipe. It serves as an air passageway and helps clean inspired air. 

f. Bronchi. 

The bronchi are tubes that direct air into the lungs. Bronchi divide and redevide forming fine airways called bronchioles. 

g. Lungs. 

Human beings have two lungs. Each lung has a network of air sacs, called alveoli, and capillaries. Each air sac is the site of gas exchange between the air and the blood.

6                                

Functions of the respiratory system 

The respiratory system performs the following functions:

1. Regulation of blood pH. 

The respiratory system removes CO2 from blood and, therefore, helps in maintaining normal blood pH.  

2. Production of angiotensin-converting enzyme (ACE)

The ACE helps in blood pressure regulation. 

3. Voice production.

Air moving past the vocal folds produces sound and therefore makes speech possible.

4. Olfaction. 

The nasal cavity has the olfactory epithelium therefore, the sensation of smell occurs when airborne molecules are drawn into the nasal cavity 

5. Protection. 

The respiratory system serves as the first line of defense providing protection against some microorganisms by preventing them from entering the blood. 

Importance of the respiratory system

    Breathing is necessary because all living cells of the body require oxygen and produce carbon dioxide. The respiratory system exchanges these gases between the air and the blood, and the cardiovascular system transports them between the lungs and the body cells

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Eid Mubarak

Eid Mubarak 

May this Eid bring you joy, peace and blessings. 

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White Moss Rose

White Moss Rose (Portulaca grandiflora), is a succulent flowering plant. Portulaca grandiflora is a well-known ornamental garden plant. Portulaca is classified in the family Portulacaceae. This genus has over a hundred species. These flowering plants are mostly found in the tropics and warm temperate regions. Portulacas are also known as the purslanes. Common purslane (Portulaca oleracea) is widely consumed as an edible plant. Pickled purslane stems are consumed in Armenia.

Location: Nowshera (KP, Pakistan)

Photography: Qaziwaheed 

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Basic types of tissues in root, shoots and leaves

Roots, shoots, and leaves all contain three basic types of tissues: 

    1. dermal tissues

    2. ground tissues

    3. vascular tissue 

Dermal tissue includes the epidermis. The epidermis forms an outer protective covering for the plant. It is one cell layer thick in most plants.  

Ground tissue includes the cortex of the stem and mesophyll of leaves. Ground tissue cells function in storage, photosynthesis, and secretions. 

Vascular tissue conducts fluids and dissolved substances throughout the plant body.  

Vascular plants have roots and shoots

A vascular plant consists of a root system and a shoot system. 

Root System 

The root system anchors the plant into the soil, from which it absorbs water and ions. Roots evolved as an adaptation to living on land.

Shoot System 

The shoot system consists of the stem, leaves, flowers, and ultimately, fruits and seeds. Stems serve as an attachment surface for leaves. leaves are the principal sites of photosynthesis. Flowers are the reproductive organs of the plant. 

The shoot also consists of repeating internode, node, and axillary bud. An axillary bud is a lateral shoot apex that gives rise to new branches or replaces the main shoot if it is eaten by an herbivore.

Roots and shoots grow at their tips, called apices (singular, apex).

Sex determination in drosophila

Sex determination in drosophila

In Drosophila, males are XY, but sex not only depends on the presence of a Y chromosome.  Drosophila is a diploid organism with a pair of sex chromosomes (XX or XY) and three autosomal pairs of chromosomes (two autosomal sets). Sex depends on the ratio of the number of X chromosomes to the number of autosome sets.

An X: A ratio of 1.00 or higher produces a female whereas an X: A ratio of 0.5 or lower produces a male. The X: A between 0.5 and 1.0 produces intersex. 

Basic Definitions (Inheritance - Intermediate Part II)

Basic Definitions

Inheritance: Inheritance is the process of character transmission from individuals of one generation to the next. It is regulated by the genes present on chromosomes.

Genetics: The branch of biology concerned with the study of inheritance, or the transmission and expression of genetic information.

Character: Any heritable feature or characteristic of an organism is known as a character e.g. Height, Intelligence, blood group, and hair color.

Trait: A Variant of a character is called a trait e.g. black or brown hair color, and short or tall stature. These are characteristics that an organism displays. Also include the organism’s behavior (behavioral traits).

Gene: Gene is the unit of heredity. It is a segment of DNA that contains the information to make a functional protein.

Allele: Alleles are the alternative form of a specific gene. Alleles Control the same characteristics (e.g. hair color) but produce different effects (e.g black or red)

Back cross: Back cross refers to a cross of F 1 hybrids to individuals with genotypes of the parental generation or with its parents.

Test cross: A cross between a recessive individual and a dominant individual whose genotype is unknown (Homozygous or heterozygous) is known as a test cross.

Pure breeding: An individual with two identical alleles of a particular gene or an individual that when self-crossed produces progeny of its own type.

Hybrid: An individual that has two different alleles of a particular gene A progeny individual from any cross involving parents of different alleles.

Dominant Allele: An allele that determines the phenotype in the heterozygous condition. For example, if a plant is Tt and has a tall phenotype, the T (tall) allele is dominant over the t (dwarf) allele.

Recessive allele: A gene that is masked by the presence of a dominant gene is called recessive.

Reciprocal Crosses: A pair of crosses in which the traits of the two parents differ about gender. For example, one cross could be a red-eyed female fly and a white-eyed male fly, and the reciprocal cross would be a red-eyed male fly and a white-eyed female fly.