Category: 12th Zoology

Bacterial Genetics

In bacteria the cells have a single circular strand of DNA. It is not
associated with proteins as are eukaryotic chromosomes. The bacterial genes,
like the eukaryotic genes possess the features of replication, phenotype
expression, mutation and genetic recombination etc. In bacteria the genetic
recombination results from three types of gene transfer viz., conjugation,
transduction and transformation. (Bacterial Genetics)

Conjugation involves the transfer of some DNA from one bacterial
cell to another followed by the separation of the mating pair of cells. In this,
large segments of the chromosomes and in special cases the entire
chromosome may be transferred.

Bacterial transformation is a process in which cell free or naked DNA
containing the genetic information is transferred from one bacterial cell to
another. It was discovered by an English health officer, Griffith in 1928. The
transforming principle was identified as DNA by Avery Macleod and Mc
Carthy in 1944. (Bacterial Genetics)

In transduction, a bacteriophages acts as a vector, transfering a portion
of DNA from one bacterium (donor) to another (recepient). If all fragments
of bacterial DNA have a chance to enter a transducing phage, the
process is called Generalized transduction. On the contrary if a few restricted
genes of the bacterial chromosomes are transduced by bacteriophage,
it is called specialized transduction. (Bacterial Genetics)

Bacteria Structure Culture

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Post date October 22, 2018
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Bacteria Structure

The structure, size and arrangement of bacterial cells consitute their
morphology. (Bacteria Structure)

The various morphological features are
1. They are spherical or rod like or spiral shaped.
2. The arrangement of cells in pairs, clusters, chains, trichomes and filaments
etc.
3. The appendages are visible by special staining techniques or by electron
microscopy. (Bacteria Structure)

The above three features represent the gross morphological
characteristics, which are of taxonomic importance in bacterial species
identification. In addition, the bacterial cells possess elaborate internal
structures, which constitute microbial cytology and bacterial anatomy. (Bacteria Structure)

Bacterial Culture

All bacteria need nutrients for their growth. They need a nutrient
medium for their growth and culture. A bacteriological medium is composed Bacterial transformation is a process in which cell free or naked DNA
containing the genetic information is transferred from one bacterial cell to
another. It was discovered by an English health officer, Griffith in 1928. The
transforming principle was identified as DNA by Avery Macleod and Mc
Carthy in 1944.

Viral Diseases

A. Cancer and Viruses

Viruses have been identified as one of the causative agents for
cancer or tumour. Such tumour inducing viruses are called oncogenic
viruses. Adenoviruses, polioma virus, simian virus 40 (SV 40), Epstein-Barr
virus (EBV) ( a herpes virus) are oncogenic DNA viruses. The RNA sarcoma
viruses are oncogenic RNA viruses (eg., Rous sarcoma). Viral Diseases

B. Rabies Virus and Rabies disease

Rabies virus belongs to the rhabdovirus family. It is a parasite of
domestic and wild mammals. The transmission to humans occurs through the
bite of an infected animal. Dogs, cats, bats, are the mammalian animal sources
for the rabies virus.
In humans, the symptoms of rabies are severe headache, high fever,
alternating excitement and depression, muscular spasms in throat and chest,
hydrophobia etc. The incubation time in humans is usually about 3 to 8 weeks
but it may also vary. If untreated the mortality rate from rabies is 100 percent.
The new rabies vaccine was discovered in 1980. It is an inactivated
vaccine prepared from the virus propagated in cultures of diploid human
cells. This vaccine is both safe and highly immunogenic. Viral Diseases

C. Pox virus

Pox viruses are the largest of all viruses and are brick shaped. They
contain double stranded DNA, protein and lipid. They have a dum bell shaped
nucleoid surrounded by two membrane layers.
Variola virus is called the small pox virus. It is transmitted by droplet
infection either directly from the infected person or by handling articles
infected by the patient. Small pox is completely eradicated. The small pox
vaccine consists of vaccinia, closely related to variola. It gives protection
both by humoral and cell mediated immunity.
Other pox viruses are chicken pox and measles viruses. Viral Diseases

D. Hepatitis-B

Hepatitis B virus (HBV) is an enveloped virus with a double stranded
DNA. This causes jaundice and hepatic carcinoma. This disease is deadly
and more infective than AIDS. HBV vaccine consists of purified HBV Ag
(Australian antigen) obtained from the blood serum of apparently healthy
carriers. Viral Diseases

Virus Culture

Cultivation (culture) of Animal viruses (Virus Culture)

Viruses can grow only in living cells. However the culture of viruses
is possible nowadays. The most economical and convenient method of
cultivating a wide variety of animal viruses is the ‘chicken embryo technique’.
In this technique, fertile chicken eggs incubated for 5 to 12 days are
inoculated with the virus particles through the shell, aseptically. The opening
may be sealed with paraffin wax. The eggs incubated at 36oC are ideal sources
for the growth of viruses.

Chick embryos contain several different types of cells in which
various viruses will undergo replication. The yolk sac is a general ideal
medium for the growth of viruses.
Viral cultures are of three types viz., Primary cell cultures, diploid
cell strains and continuous cell lines.

1. Primary culture: Virus Culture

Primary cell culture are derived from normal tissue of an animal such
as mouse, hamster, chicken and monkey or a human being. When cells from
these tissues are processed and cultured the first monolayer is referred to as
the primary culture. A monolayer is a confluent layer of cells covering the
surface of a culture vessel.

2. Diploid cell strain: Virus Culture

Diploid cell strains are derived by primary cell cultures from a
specific tissues like lung or kidney which is of embryonic origin. These
diploid cells are the most employed host of choice for the production of
human vaccine virus.

3. Continuous cell lines: Virus Culture

Continuous cell lines are capable of an infinite number of doublings.
Such cell lines may arise with the mutation of a cell strain or more commonly from the established cell cultures from malignant tissue. Many viruses, which
are difficult or impossible to grow have been cultured in continuous cell lines.

Viral genetics

The viral genome contains all the genetic information either as DNA
or RNA. but never both. The proportion of nucleic acid in a virion varies
from 1 % as in influenza virus to about 50%, as in certain phages. Smaller
viruses like paraviruses may have 3 to 4 genes while larger viruses like
herpes and pox may have several hundred genes. Viral genetics

Virions contain only a single copy of the nucleic acid. Hence they are called haploid viruses. The only exception is the retroviruses, which are said to be diploid as they contain two identical single-stranded RNA genomes. The virions are called the infectious particles. Viral genetics

The structure of nucleic acid in the virion may be either linear or
circular. The DNA of most animal viruses in a linear molecule. In some plant
viruses the genome is a circular RNA. But the RNA in animal viruses exists
only as linear double stranded or single stranded molecule. Viral genetics

Structure of Viruses

Viruses

Structure of Viruses :- Viruses are infectious agents. They are much smaller than the bacteria. Their approximate size ranges from 20 to 300 nm. Viruses are
incapable of independent growth in artificial media. They can grow only in
animal or plant cells or in microorganisms. Hence they are referred to as
obligate intracellular parasites. They reproduce in these cells by replication.

Replication is a process in which many copies or replicas of the viral
component are assembled and made to represent the progeny. They lack
metabolic machinery of their own to generate energy or to synthesize
proteins. They depend on the host cells to carry out these vital functions. The
bacterial viruses are called bacteriophages. These viruses infect the
bacteria and multiply inside the bacterial body and cause the lysis of bacteria
(lytic cycle) or integrate themselves with the bacterial genome (lysogeny).

Structure of Viruses:

Animal and plant viruses are composed of a central core of nucleic
acids surrounded by a protein covering called capsid. The capsid is made up
of units called capsomeres. Viruses exhibit a characteristic symmetry,

1. Spherical viruses are isohedral, 2. Rod shaped viruses are helical in
symmetry. Certain group of viruses are complex in symmetry.

Some animal viruses, in addition to the nucleocapsid structure
contain an outer membrane like structure called the envelope. The envelope
is made up of lipoproteins. The envelope conceals the symmetry of viruses.
Virions with envelopes are sensitive to lipid solvents such as ether and
chloroform. On the other hand, the naked virions are not affected by the
lipid solvents.

Isohedral viruses such as adeno viruses, SV15, polio viruses and
blue tongued viruses are spherical in shape and their surface is a lattice with
identical triangular units.

Helical surface symmetry and structure are characteristic of tobacco
mosaic virus(TMV) and animal viruses that cause diseases such as measles,
mumps, influenza and rabies. In these, the nucleo capsid is a flexible
structure packed within a fringed lipoprotein envelope. The fringes are made
of glycoproteins. In TMV the nucleic acid core is covered by a capsid
consisting of closely packed capsomeres arranged in a helix.

Complex or uncertain symmetry is seen in Pox viruses, T-bacteriophages,.
These have different proteins and lipoproteins.

Pasteur, Koch, Lister

Medical Microbiology involves the study of micro organisms that
colonize or infect human beings; the mechanism by which they cause
diseases; the body’s response to infection and specific antimicrobial
prevention and treatment.

The contribution of Louis pasteur (1822 – 1895) in France in the
field of microbiology lead to a greater understanding of human ailments and
animal diseases. Much of Pasteur’s work involved the growth of bacteria
and yeasts in liquid cultures. He developed methods of sterilization and of
pasteurization. Pasteur (1857) observed different kind of microbes
associated with different kinds of fermentation. e.g. Spheres of variable size
(yeast cells) within alcohol fermentation and smaller rods (Lactobacilli) with
lactic fermentation. This finding led Pasteur to state that specific microbe
may cause specific disease in man.

His crowning achievements were Pasteurisation of milk, the
development of techniques to reduce the virulence of infectious organism,
without eliminating their capacity to produce immunity. In this way he
developed vaccines, for the control of “cholera” “anthrax” and “rabies” in
man.

Robert Koch – (1843 – 1910)

Robert Koch, a younger contemporary of Pasteur, made his
contributions on new procedures for staining, visualizing and growing
bacteria. He solidified liquid culture media with agar. He also isolated and
characterized the bacilli of anthrax, and tuberculosis and demonstrated their
causative role by a series of experiments.

After identifying the tubercle bacillus, Koch has advocated his
postulate, in order to distinguish a pathogenic microbe from adventitious
microbes. The impact of his work towards the end of 19th century lead to
the discovery of “specific toxins” made by the causative bacteria for
diphtheria and tetanus and “antibodies” produced in host animals against the toxins to neutralise their effect. His finding also lead to immunization therapy.
He was awarded the Nobel Prize in the year 1905 for his work on
tuberculosis.

Contributions of Joseph Lister : (1827 – 1912) to microbiology is the
technique of “pure culture” of bacteria. The growth of a mass of cells of the
same species in a laboratory vessel / test tube using serial dilutions in the
liquid media is called pure culture. Lister obtained a pure culture of the
organism Bacterium lactis and also found the importance of pure culture
which form the suitable media for the growth of micro organisms, reponsible
for infections, fermentation, nitrogen fixation in soil, etc. The pure culture
techniques lead to developments in modern microbiology.

On the basis on Pasteur’s evidence, in 1860 Joseph Lister,
discovered a system for “antiseptic” surgery. This system prevents the
surgical wound infection and other lethal complications.

Microbiology Introduction and History of Medical microbiology

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Post date October 17, 2018
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Microbiology Introduction

Microbiology Introduction and History of Medical microbiology

The world of microorganisms includes various species of
bacteria, viruses, fungi and protozoan parasites. The discovery of
microscope and the ingenius techniques of isolation and identification of these
microbial organisms opened up a new field of study named Microbiology.
This study deals with the form, structure, reproduction, physiology,
metabolism and classification of micro organisms.

The area of microbiological studies include various aspects of their distribution in nature, their relationship to each other and to other organisms, their effects on plants, animals and human beings, their roles in the sustainability of environmental habitats such as soil, air and water and also their beneficial aspects to biotechnology.

History of Medical microbiology

The medical microbiology had its origin in the year 1888 when the
Pasteur Institute in Paris (France) was established. Robert Koch
became the Director of the Institute For Infective Diseases. Both Louis
Pasteur and Robert Koch infused the spirit and interest to gain knowledge in
medical microbiology to the countrymen of America and Europe.

The medical microbiology deals with the aspects of infection, the causative agents of infection and the diseases due to infection. Following the establishment of Germ Theory of Diseases by Pasteur, innumerable infectious diseases that
haunt the human population were discovered. For most of these infectious
diseases, the drugs and vaccines have been found.

Unit 3 – Immunology Topic List Zoology

12th Zoology

Birth control

The population problem is assuming serious proportions in many
developing countries. In India, the population which was about 400 million in
1960 is now 100 crores or 1000 million. Realizing the dangers inherent in
population growth, the government of India has taken several measures to
check population growth and have given family welfare programmes an important
place in the five year plans. The World Health Organization (WHO)
has also stressed the importance of family planning in the Global Strategy for
Health for All by 2000 AD.

The National Family Welfare programme is a comprehensive scheme
which includes:

1. Maternal and Child Health Care (MCH)
2. Immunization of mothers, infants and children.
3. Nutritional supplement to pregnant women and to children.
4. Contraception with health education, to motivate couples to accept
contraceptive methods and to adopt small family norms.

Contraception :

Contraception is the prevention of pregnancy resulting from coitus.

Barrier Methods for Birth control

Prevents entry of sperms into vagina or uterus.

(a) The Condom: The male wears a condom which covers the erect
penis, and prevents deposition of sperms in the vagina. Condoms are made
of rubber from latex. Ejaculated semen is retained within the condom
preventing their entry into uterus. In India thin condoms called Nirodh, are
manufactured and widely used. Condoms can be combined with spermicides
inserted into the vagina. Condom also protects against sexually transmitted
diseases (STD) like syphilis, AIDS.

(b) The Diaphragm (cervical cap): Women can wear a vaginal
diaphragm fitting into the vagina or a cervical cap fitting over the cervix.
They prevent entry of sperms into the uterus. They are made of synthetic
rubber or plastic, and are used in combination with chemical spermicides.

Hormonal Methods for Birth control

Hormones are prescribed as pills, implants, or injections. Some
hormonal contraceptives contain only progestin, which is a type of female
hormone and some contain a combination of both (combined pill)
progesterone and oestrogen and prevents ovulation. Hormonal methods are nearly 99 percent effective. The effects of Hormonal method stops (interfere)
the mechanism of ovulation. They can also stop the mechanism of conduction
of ovum along the fallopian tubes. The hormones interfere in the thickening
of the endometrium and they may also cause the formation of mucus in the
cervix and vagina to prevent the penetration of sperms.

Mechanical Methods for Birth control

The intrauterine device (IUD) and intrauterine system (IUS) are
contraceptive devices inserted into the uterus. Copper-T is a synthetic T
shaped device made up of copper and plastic (non irritant), is placed inside
the uterus. This can remain for a period of 3 years. This also helps to give
adequate time inerval between pregnancies.

Surgical Methods for Birth control

Surgical contraception, or sterilization, is an operation that makes a
person infertile. This surgery can be carried out in men (vasectomy) and
women (tubectomy).

Vasectomy is the method of permanent birth control in male in which
the removal of a part of the vas deferens and ligations are performed. It is
simple in all aspects. Male sterilization is not immediately effective. The seminal
vesicles still contain sperm after the operation, and a condom must be used
until semen analysis shows that no sperm are left. Tubectomy is the method
of permanent birth control in female, here a portion of fallopian tube is cut of
and the cut ends are ligated to prevent fertilization. Female sterilization is
effective immediately, but the risk of ectopic pregnancy is slightly increased.

Fertilization

The union of the egg and the sperm is called fertilization. It results in
the production of a single diploid cell called zygote.

At the time of ovulation, the ovum is fully matured and it enters the
infundibulum of the uterine tube and passes into the ampulla. Fertilization of
the ovum occurs in the ampulla of the uterine tube. One spermatozoan pierces
the egg membrane, zona pellucida and enters the ovum. Polygamy (entry of
more sperms) is avoided by the formation of fertilization membrane around
the ovum.

In vitro fertilization (Test tube babies)

The so called test tube babies are produced by the technique of in
vitro fertilization. (In vitro = outside the body, as against in vivo = within the body). This technique is being increasingly used in couples who are not
able to achieve fertilization in the normal way

Gonadotropins are administered to the woman to stimulate growth
of follicles in the ovary. Just before ovulation, the ovum is removed (using an
aspirator) and is placed in a suitable medium. Spermatozoa are added to the
medium. Fertilization and early development of the embryo takes place in
this medium.

The process is carefully monitored. When the embryo is at the
8-celled stage, it is put inside the uterine endometrium. Successful
implantation takes place in about 20 percent of such trials. The techniques
are complex and need a team of well trained experienced personnel with
high degree of skill.

The success rate is only about 20% and 2 or 3 attempts may be necessary. It is also very expensive. The first success with this technique was achieved by Steptoe and Edwards of UK in 1978. However successful ‘test tube babies’ have been produced in many countries including India.

Gamete Intra fallopian transfer (GIFT)

It is a newer method in which the fertilized ova are introduced into
the fallopian tube from where they naturally pass to the uterus for
implantation. This method is considered to have a higher success rate than
IVF. An even newer technique is the introduction of a single sperm into the
ovum by microinjection.

Bacterial Genetics

Related Topics in Zoology:

Bacteria Structure

Bacterial Culture

Related Topics in Zoology:

Viral Diseases

A. Cancer and Viruses

B. Rabies Virus and Rabies disease

C. Pox virus

D. Hepatitis-B

Related Topics in Zoology:

Virus Culture

Cultivation (culture) of Animal viruses (Virus Culture)

1. Primary culture: Virus Culture

2. Diploid cell strain: Virus Culture

3. Continuous cell lines: Virus Culture

Related Topics in Zoology:

Viral genetics

Related Topics in Zoology:

Viruses

Structure of Viruses:

Related Topics in Zoology:

Pasteur, Koch, Lister

Robert Koch – (1843 – 1910)

Related Topics in Zoology:

Microbiology Introduction

History of Medical microbiology

Related Topics in Zoology:

Unit 3 – Immunology Topic List Zoology

Birth control

Barrier Methods for Birth control

Hormonal Methods for Birth control

Mechanical Methods for Birth control

Surgical Methods for Birth control

Related Topics in Zoology:

Fertilization

In vitro fertilization (Test tube babies)

Gamete Intra fallopian transfer (GIFT)

Related Topics in Zoology: