The smallest unit of life that is capable of independent existence.

It occurs in all living organisms, both plants and animals.

3 to 30 microns (1 micron = 1/100 mm).

0.2 to 0.5 microns - belongs to bacteria.

The cell of an Ostritch egg (infertilized). It is about 18 cm/7 inches in dia.

The average diameters of a cell is between 1/50 to 1/100 millimetres. It is surrounded by a strong membrane, which is almost 1/500000th of an inch thick. Each cell has a dense kennel called "Nucleus", which controls the activities of all other cells. Outside the cell nucleus is the Cytoplasm, a gelatinous substance. The nucleus is enclosed in a thin but strong membrane called nuclear envelope and contains chromosomes.

Robert Hook of England, in 1665, identified the cell, and named it so, from a section of corn.

1824 - by RJH Dutrochet - French..

Robert Brown - Scotland - 1831.

Hugo Von Mohl, Germany.

Every cell is surrounded by a membrane through which the cell takes in what its needs from the outside atmosphere and discharges what is superfluous. Within the membrane lies the liquid called Protoplasm.

Nucleus: controls and directs the activities of all the other parts of the cell.
Cytoplasm: The remainder of the protoplasm where many of the viral activities of the cell takes place.

(1) CELL WALL: Found only in plant cells and consists of non-living substances like Lignis, Pectin, Cellulose, etc.
(2) CELL MEMBRANE: called Plasma lemma. It is the outer membrane of the cytoplasm found both in animals and plants and contains living substances like protein etc.
(3) ENDOPLASM RETICULUM: A network of tubes or channels of membrane in the Cytoplasm which helps in the protein synthesis and conduction of material.
(4) RIBOSOMES: Externally small, dense, granular, spherical bodies found in a free state in the cytoplasm, comprising of RNA (Ribose Nicleic Acid) and Proteins. They help in synthesis of proteins from amino acids.
(5) GOLGI BODIES: Bag like structures formed of stocks of membrane. In plants they are called dictyosomes. They secrete various substances and help in the formation of cell plate during cell division.
(6) VACUOLES: A fluid filled sac within a cell. In plant cells they are very big and surrounded by a membrane called Tonoplast, whereas in animals they are very tiny. Their function is Osmo-regulation and maintains cell turgidity.
(7) MITOCHONDRIA: Rod like or spherical semi solid structures containing DNA - (Deoxyribose Nucleic Acid) in their matrix along with some enzymes which are found in all cells. They synthesize ATP - the energy storing molecules.
(8) PLASTIDS: Small bodies found in the cells of higher plants. They are of two types: (A) Leucoplasts: Colourless and stores starch, protein or lipids. (B) Chromoplasts: Coloured and are of two types. (i)Non-photosynthetic: Chromoplasts which provide color to flowers, fruits and leaves. (ii) Photosynthetic: Chromoplasts which in green plants manufacture food from carbon-di-oxide and water in the presence of sunlight.
(9) NUCLEUS: They are differently shaped - oval, cylindrical or elongated. Each nucleus in bound by the nuclear membrane which contains nucleoplasm - which consists of "Chromatin" and "Necleoli". Chromati consists of DNA, RNA and proteins. The nucleus controls all cell activities and it is responsible for heredity characteristics and assists in cell division.
(10) CENTROSOME: A rather dense area of protoplasm lying close to the nucleus. Usually found in animal cells. In the middle of the centrosome are two small dot like bodies called centroils. They form a spindle in lower plants during cell division.
(11) CILIA AND FLAGELLA: These are fine extensions of the cell surface and are similar in structure. Their functions are to help in locomotion or movement and in some animals they also help in feeding.
(12) CELL INCLUSION: These are non living substances present either in the Cytoplasm of the cell or in the vacuoles. In animal cells the inclusions are in the form of secretary granules as in Zymogen granules, Haemoglobin in RBC, food material in the form of glycogen in liver cells, pigments as in the cells of skin, eye and hair. Whereas in plant cells they are in the form of food particles such as starch, oil, globules or excretory products like resin, gum etc.

Plant cells consisting of Lignin, Pectin and Cellulose.

Plasmalemma.

Synthesis of proteins from amino acids.

Only in higher plants.

Oval, Cylindrical or elongated.

Nucleus of the cell.

Nucleus - chromatin to the exact.

Centrosome.

Growth and development of all living things depend upon the growth of cells in size and division whereby increase in number take place.

There are two kinds - (1) Mitosis, (2) Meiosis.
MITOSIS: Also called Somatic cell division. Literally it means divisions of nucleus but it is generally described as cell as a whole- both nucleus and cytoplasm. It results in formation of two daughter cells with equal number of chromosomes in each, which occur in somatic cells or organs. It is the most common form of cell division which is essential for cell multiplication and growth. Since the number of chromosomes remains the same during mitosis, this division is also referred to as the equational division.
MEOISIS: Occur in reproductive cells. It causes a reduction in number of chromosomes in the cell, besides formation of gamets which contain half the number of chromosomes. Since the daughter cells have half the number of chromosomes as compared to the mother cell, this division is also called the "Reductional Division". It causes hereditary variation in a species due to exchange of genetic material. Note: Before cell divisions, the cell prepares itself for division and is called "interphase", in which the cell becomes more active. Each cell division has two steps viz (1) Division of the Nucleus and (1) Division of the cytoplasm. During all division chromatic material of the cell gets organized into chromosomes.

All biochemical reactions of processes taking place in the living organisms. There are two aspects of it interwoven to each other:
(1) Anabolism: Synthesis of complex organic molecules from simple molecules by the living organisms. It is the constructive or synthetic phase of metabolism. Eg: The formation of proteins from amino acid.
(2) Catabolism: Breakdown of complex molecules into simple molecules to release energy, that is, bearing down of hydrocarbons into simpler forms with the release of energy. Metabolism takes place in a controlled manner at body temperature. Enzymes act as bio-catalysts in the process. The energy released in such reactions is stored and used for growth and development. The elimination of waste products generated in the process is called excretion.

Respiration in biological terms has two distinct expressions: (1) Breathing - the inhaling and exhaling. (2) The transport of oxygen and carbon-di-oxide to and from the cells. It is called as external respiration. The internal respiration or cell respiration occur within the cell and constitutes the chemical reactions from which an organism derives energy. Internal respiration using oxygen is termed "aerotic", while anaerobic respiration may occur in the absence of oxygen. Both plants and animals (or, all living organisms) respire.

(1) Skin Breathing: Carried out through the skin by slow moving animals.
(2) Gill Breathing: By fishes - The Gills absorb oxygen from water flowing over them, taken in through the mouth.
(3) Tracheal Breathing: System developed by insects which include network of tubes.
(4) Lung Breathing: Acquired by evolved animals.

To release the energy present in their food and to get rid of the waste - carbon-di-oxide.

It is the union of two gametes or sex cells to produce a zygote or fertilized egg which grows into a new off-spring.

External: This type of fertilization mostly or normally occur with water creatures and lower plants. Eg: Frogs, Toads and Ferns (Plant). In this, the male gamete travels across the watery surface and fertilize the female gamete or egg, which then develops into an individual creature.
Internal: Occurs with mammals, birds, reptiles and insects. In the calse of birds and reptiles the sperms are shed directly into the female's body where it is fertilized before they are laid. Eg: Birds and Reptiles.
In the case of mammals, the cell develops into an embryo within the female body. The fertilization process in plants is also external but a complex process, explained under Plants.

Each square inch of skin of the human body contains about a million cells. The brain is made of 30 million cells and our blood contains about 20 trillion cells.

They are carriers of gene - hereditary traits.

Chromosomes are always found in pairs and vary in number in each species of living organisms. Human cells have 23 pairs (46 in all).

Herber McLean  Ivans of USA.

In every chromosome there are proteins molecules and two kinds of nucleic acid molecules called RNA (Ribose Nucleic Acid) and DNA (Deoxyribose Nucleic Acid). The DNA is concentrated in the chromosomes while RNA is concentrated in the nucleoli, both of which is present in the nucleus.

A, G, T, C.

The four DNA bases, A, G, T, C can be used to store information. This genetic information is passed on via. RNA (which consists of four bases - adenine, guanine, cytosine and urasil) which provides a template for the assembly of amino acids in a particular sequence, thereby building a protein. A group of three DNA and RNA bases is known as a triplet of codon, and codes for a particular amino acid. Information is passed from DNA to RNA by complimentary pairing, which is called the Genetic coding or Engineering.

"Gene" is a hereditary unit located in chromosome transmitting physical and mental traits from parents to off-spring (children) through the base units of DN

Gregor Mendell in 1896.

Wilhelm Johannsen - Denmark.

Dr. Hargobind Khorana, an Indian born American scientist, successfully created an artificial Gene in a test tube in 1970 by protein synthesis (He received Nobel Prize in 1968).

It is the Code of life by which inherited characteristics pass from generation to generation. It is expressed by the molecular configuration of chromosomes of cells, which the code bearing material is DN

The artificial manipulation of parental genes to form combinations to give birth to a new organism with predetermined mental and physical characteristics. It is also called the Bio-Engineering.

DNA was first discovered in 1953.

Recombinant DNA or Gene splicing. It was developed in 1973.

Of the 23 pairs (46 in all) of chromosomes, 22 pairs are similar and the other only pair is dissimilar and are sex chromosomes called X and Y. Two X chromosomes produces a female and an X and Y chromosomes produces a male. Thus, the sex of the child depends entirely on whether the female egg is fertilized by an X carrying sperm or Y carrying sperm.

Study of similar traits passed from parents to their off-spring (children).

It is a branch of medical science which deals with the study of hereditary material passing from one generation to another. In simple terms it is the transmission of physical, mental and bio-chemical characteristics from parents to children.

(1) To understand the underlying cause of the disease and the means of transmission. (2) To understand the reasons of normal variations. (3) To apply the knowledge to prevent genetic disorders through counseling and antenatal diagnosis. (4) The knowledge can be applied to solve disputed parentage or traits of murderer etc.

(1) Anabolism: Synthesis of complex organic molecules from simple molecules during metabolism.
(2) Catabolism: The part of metabolism in which chemical substances in living things are broken down into simpler substances. The process usually releases energy.
(3) Centriole: The part of a cell which is important in the formation of a spindle during the process of a cell division.
(4) Chromatin: Hereditary substances of the nucleus. It is a net work of threads in nucleus of a cell that shows up when the cell is stained with certain dyes.
(5) Cilia: Hair like cell prolongations meant for locomotion.
(6) Coennocoeti / Coenocyte: The protoplast or cell containing many nuclei. It is found in many fungi and some green algae.
(7) Epidermis: The outer most cell layer of an organism.
(8) Fossils: Remains of an organism preserved in rocks, sands, etc.
(9) Gamete: Mature reproductive cell, that is, cell sperm, or formed in cell reproduction or reproductive/germ cell produced by male and female organisms.
(10) Gameto Genesis: The process of formation of gametes.
(11) Gene: Part of the chromosome that determine inheritance.
(12) Haploid: Characteristics of gametes which contain one set of unpaired chromosomes in the gametes or sex cells of animals.
(13) Heterochromatin: Inactive chromatin found in the nucleus.
(14) Histone: Type of protein found in chromosomes in association with the nucleic acid DN
(15) Hypodermis: Outer most layer of cortical cells beneath epidermis that acts as water storing or strengthening tissue.
(16) Hypha: Fine breached or un branched filament that spreads to form a loose network called "Mycelium".
(17) Inter-phase: A stage in cell division when the nucleus is not actually undergoing division but very actively involved in the general process. It is the period between two divisions when nucleus is said to be in inter-phase.
(18) Leucocyte: Any of the white or colorless nucleated cells occurring in blood.
(19) Leucoplast: Colorless plasticids, in the cytoplasm of plant cell around which starch collects.
(20) Meta Phase: Second stage of cell division of the nucleus during mitosis and meiosis. The membrane breaks down and a fibrous spindle forms. The spindle has two poles at opposite side of the cell; the chromated pairs align along the spindle's equator.
(21) Microsome: Cell particle of the smallest size, typically consisting of a piece of endoplasmic reticulum to which ribosome are attached.
(22) Plasmalemma: Outer living membrane of the cell. (Cell membrane)
(23) Protoplasm: The living content of cell which includes cytoplasm and nucleus. It is a jelly like colloidal substance constituting the living matter of plant and animal cells and performing the basic life functions.
(24) Prophase: First stage of cell division in which chromosomes or chromatids get aligned in the middle line to form a spindle, the chromosome appear as two sister chromatids, which coil and then shorter and thicker.
(25) Ribosome: Any of the numerous spherical cytoplasmic particles consisting of RNA and protein that are the sites of proteins synthesis in the cell.
(26) Spindle: Structure seen in the cell at the time of cell division.
(27) Telophase: Last stage of cell division in which the nucleus starts returning to the interphase stage. A nuclear membrane forms around each pair of daughter chromosomes, thus erecting two complete daughter cells.
(28) Viruses: They are nucleoprotein in nature, but a particular virus has either DNA or RNA never both. Thus they posses the characteristics of both the living and non-living. They are the threshold of life.
(29) Xygot: A cell formed by fusion of a male and female gamete or fertilized egg, that is a fertilized egg or ovum.

(1) Cytogenetics: Gives the knowledge of structure of nucleus of cell and its past, i.e., chromosomes which normally lies in the condensed form in the nucleus.
(2) Clinical Genetics: Application of the knowledge of genetic material responsible for certain diseases and their transmission from one generation to another. It includes the investigative and preventive methods adopted for diagnosis and preservation.
(3) Biochemical Genetics: Deals with the biochemistry of genetic material for normal metabolic process. It includes immuno-genetics and blood groups i.e., genetic material concerned with the mechanisms of producing antigens and antibodies.
(4) Eugenics: The field dealing with the clinical applications of principles of heredity for the betterment of mankind.
(5) Environmental Genetics: Deals with the manipulation of genetic material in living form by recent advanced technologies of genetic engineering and recombinant DNA
(6) Molecular and Developmental Genetics: Deals with molecular structure of the genetic materials, its significance during embryogenesis and functional state of individuals during normal as well as abnormal conditions.
(7) Physiological Genetics: The field elucidates the normal functions of various organelles of a cell governed by the genetic material.
(8) Population Genetics: Deals with the distribution and behaviors of genetics material in a particular population so that the genes and the genotype frequencies are maintained or changed.
(9) Radiation Genetics: Deals with the effects of various types of radiation or genetic material producing various diseases.
(10) Pharmaco Genomics: The science of knowing how the people with different genes respond to various classes of drugs.

Bacteria.

Gregor Mendel, Austria.

Cell wall.

A network of tubes or channels of membrane in the cytoplasm which helps in protein synthesis and conduction of material.

Ribosomes.

Mitochondria.

Consists of DNA, RNA and proteins.

Mitosis.

Ability to reproduce.

Mitosis.

Protein synthesis.

Drosophila.

Defence mechanism.

Hormonal immunity.

The appearance of two or more characteristics which are controlled by a single gene.

Population genetics.

Total number of different kinds of genes pooled by all the members of a population.

Tissue.

Theodore Sehwann and Mathias Jakob Sehleiden.

Mitochondria.

Hippocrates.

Gene.

Neuron.

Female ovum.

Male sperm.

Oncogenes.

Robert Weinberg and his team.

George Gamo.

A.D. Watson and F.H.C. Criek.

Ribosomes.

Centriols.

Pepsinogen.

Gregor Mendal.

DNA

ATP molecules.

Nucleo Tides.

Mitosis.

Genotype.

Uracil

Gene Splicing.

A chemical that triggers a natural behavioral response in another nuclear of the same specie. This includes alarm, food trail and sex pheromones and many other that affects the behavior or physiology.