Genetics

• Genetics word first used by => W. Watson (in 1905).
• Transmission of character from one generation to next generation is called Heredity.
• The process of transfer of hereditary character from generation to generation called as Genetics.
• The characteristics which transmit from generation to generation is transported by Gene.

Gene: Gene word first coined by => W. Johannsen (in 1909). It is a unit of hereditary material located on chromosome. Gene itself or with other gene determine character of organism. Gene exist in number of alternative forms termed as alleles. Gene occasionally undergo for radial changes called as Mutation. The modern concept of perception about the gene was given by => Benjer (in 1956). Functional unit of gene => Cistron Unit of gene responsible for mutation => Muton Unit of gene take a part in recombination => Recon In Human 35000 gene are present.

• Gregor Johann Mendel said that hereditary character is transfer by gene.
• Hence Gregor Johann Mendel is known as Father of Genetics.

Mendel's Experiment:

• Mendel chooses 7 pair of pea plant species for his experiment.

 

Characters	Dominant characters	Recessive characters
Shape of the seed.	Spherical smooth seed.	Wrinkled seed.
Color of the cotyledon.	Yellow	Green
Color of flower.	Red	White
Shape of the fruit.	Smooth	Shrinked
Color of the fruit.	Green	Yellow
Position of the flower.	Tall	Farthest
Length or Height of the plant.	Tall	Dwarf

Mono-hybrid Cross:

Mendel made cross between 2 pure plant having contracting character for single trait called Mono-hybrid cross (i.e. Tall & Dwarf plant for height)

 

Phenotype ratio => 3 : 1

Genotype ratio => 1 : 2 : 1

Di-hybrid Cross:

Mendel made cross between 2 pure plant having in 2 pair of contracting character i.e. color & shape of seed called Di-hybrid cross. (i.e. Plant having round seed with yellow color & wrinkle seed with green color.)

 

Phenotype ratio => 9 : 3 : 3 : 1

Genotype ratio => 1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1

 

Mendel's Law of Heredity:

• On the basis of mono-hybrid and Di-hybrid cross Mendel proposed law of heredity.

1. Mendel's First Law: (Law of dominance)

• According to it when two dissimilar unit factors are present in an individual only one is able to express.
• One that express itself is dominant character while which fail to express is recessive character.
• In the first generation only the dominant character is visible, while the recessive character is hidden and it appears in the next generation.

 

2. Mendel's Second Law: (Law of segregation)

•  According to this law during the gametes formation both the character which governed by gene is segregated and out of these factors only one factor is reached in the gamete.
• Both factors never come at a time in the gamete.
• This law is also called the Law of purity of Gametes.

3. Mendel's Third Law: (Law of Independent Assortment)

•  According to this law various pairs of the factors which exist in organism are independent to each other.
• Thus organism of new appearance may born.

 

Terms Related to Genetics:

1. Phenotype:
• The characteristics of the organism which are directly & visibly appreciable is called Phenotype.

Chromosome, DNA, RNA

Chromosome:

• Chromosome name was given by => Waldeyer (in 1888)
• Chromosome is thread like structure found in nucleus.
• Chromosomes are basic constituents of genetic substance Chromatin.
• During Cell division Chromatin breaks into pieces and form Chromosome.
• Each Chromosome is made up of two Chromatids, which joint together at a point called centromere.
• On Chromosome various genes are located.
• Gene is the functional unit of DNA, made by segment of DNA.
• Characteristics which transmit from generation to generation is transported by Genes and these genes are carried out by Chromosome.
• Thus Chromosome are called as Vehicle of Heredity.

Number of Chromosome in different organism:

Organism	Number	Pair
Pigeon	40	80
Chimpanzee	24	48
Cat	19	38
Onion	8	16
Dog	39	78
Human	23	46
Frog	13	26
Pea	7	14
Horse	32	64
Wheat	21	42
Tomato	12	24
Ascaris	1	2
Housefly	6	12
Mosquito	3	6
Monkey	21	42
Tobacco	24	48

• One set of Chromosome (Haploid) is called Genome.
• Two sets of Chromosome (Diploid) found in somatic cells.

DNA: (Deoxyribo Nucleic Acid)

• First who isolated DNA from nucleus of pus cells => Friedrich Miescher (in 1869).
• DNA is Polynucleotids.
• Almost all amount of DNA is present in nucleus of cell but very small amount also present in Mitochondria and Green Plastids.
• In 1953 Watson and Crick gives double helix model of DNA, each helix has a diameter of nearly 20Å.
• DNA is macro molecule in which large number of nucleotides are present.
• These nucleotides has three components.
• Nitrogen base
• Sugar
• Phosphate group.

• Nitrogen  base of double helix form a pair with the help of hydrogen bonds.
• Adenine pairs with Thymine (A = T).
• Guanine pairs with Cytosine (G = C).
• Adenine and Thymine are complementary to each other. 
• Guanine and Cytosine are complementary to each other.
• Hydrogen bond between nitrogen base holds two strands together.

Function of DNA:

• It contain genetic information in coded form.
• DNA synthesis RNA.

RNA: (Ribo Nucleic Acid)

• It is a single standard nucleic acid but in some virus it has double standard structure like in Retrovirus.
• Main function of RNA is to assist Protein synthesis but in some plant and virus it acts like carrier of genetic substance.
• Thus in viruses genetic substances are either DNA or RNA but not both.
• RNA is made up of Phosphate, Ribose sugar and Nitrogen base.
• RNA is found in nucleus as well as cytoplasm.

RNA is of three types:

1. Messenger RNA (mRNA):
• It carries the information of protein synthesis from DNA of the nucleus to Ribosome in coded form.
• It is 3-5% of all RNA.
• It also help in selecting amino acids.

Difference between Plant cell and Animal cell

Sr. No.	Plant Cell	Animal Cell
1	Plant cells are larger in size.	Animal cells are generally smaller in size.
2	Cell wall is present and made up of cellulose and chitin.	Cell wall is absent.
3	Plastid is present.	Plastid is absent.
4	Centrosome is absent.	Centrosome is absent.
5	Vacuoles are larger in size.	Vacuoles are smaller in size.
6	Chlorophyll is present except fungi & bacteria.	Chlorophyll is absent.

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Types of Cell

Sr. No.	Prokaryotic Cell	Eukaryotic Cell
1	Nucleus is absent.	Nucleus is present.
2	Cell is small in size.  (1-10 micron)	Cell is large in size.  (5-100 micron)
3	Only one chromosome is present.	More than one chromosome is present.
4	Cell organelles, nucleolus are absent.	Cell organelles, nucleolus are  present.
5	Cell division takes place by  Fission or Budding.	Cell division takes place by  Mitosis & Meiosis.
6	Cell wall is usually present;   (Chemically complex)	Cell wall only present in plant & fungi;  (Chemically simpler)
7	Example: Bacteria, Blue green algae etc.	Example: Fungi, Plant, Animals etc.

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Cell

• Study of Cell is called as Cytology
• "Cell is known as basic structural and functional unit of all Organisms or Living beings (Life) "
• human body exists nearly 10 /\ 14 (10 to power 14) Cells.
• Cell was Invented by => Robert Hook (in 1665) {He was discovered dead cell in Bark of Cork}
• Cell has been made from a life saving substance called as Protoplasm {Protoplasm is the physical base of the life and in Protoplasm nearly 80% water is found}
• Protoplasm was discovered by => J. E. Purkinje (in 1939)
• Protoplasm is also of two types- 
• Nucleoplasm - (Present inside the nucleus)
• Cytoplasm - (Present between nucleus and cell membrane)

==========================================

Cell Theory:

• Cell theory was given by Schelder and Schwann (in 1838-39)
• Important points regarding cell theory:

1. Every organisms originates from a cell.
2. Each cell arises from preexisting cell.
3. Cell is self independent unit, it takes part in metabolic activities.
4. Core of the cell is nucleus. 

Some Important Points

* Smallest Cell => Mycoplasma gallisepticum * Largest  Cell => Egg of Ostrich (Weight - 1250 gm) * Longest Cell => Nerve Cell (Length up to 1 m)\ * Biggest single cell organism => Acetabularia

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Cell Structure and it's Functions

Cell have various type of structures like cylindrical, elliptical, spherical, transverse etc.

Cell Components:

1) Cell membrane:

• It is also called as Plasma membrane.
• It is the outermost layer of the cell.
• It is semipermeable membrane.
• In plant cell it is found within cell wall.
• It is made up of phospholipid molecules.

Function:

• Control the molecular activities between cell and it's other medium which interacts with cell. 

2) Cell Wall:

• Only present in Plant cell.
• it is made up of non living substance
• Cell wall of algae and plants are made up of Cellulose.
• Cell wall of fungi and bacteria are made up of Carbohydrates.
• Cell Wall of fungi is made up of => Chitin
•  Cell wall of bacteria is made up of => Peptidoglycan

Function:

• It protect nucleoplasm and cell membrane from external attack.

3) Protoplasm:

• Name was given by Purkinje (in 1839).
• Whole fluid present inside plasma membrane is Protoplasm.
• It is made up of water, ions, salt and organic molecules
• It is a living part of cell.
• It is divided into two parts
• Cytoplasm: Present between nuclear membrane and cell membrane.
• Nucleoplasm: Present inside nuclear membrane.

4) Mitochondria:

• It was discovered by => Altman and Benda (in 1886).
• Altman called it Bioplast and Benda called it Mitochondria.
• It's shape is cylindrical having Diameter (0.2 -1  micrometer) and Length (1 - 1.4 micrometer).
• It surrounded by double membrane(outer and inner membrane).
• Outer membrane is oily and smooth.
• Inner membrane has many folds called cristae (in plant cell it is called tubuli) and inner compartment where fluid is present called matrix.
• Function: 

• It is a site of aerobic respiration and they produce cellular energy in the form of ATP (Adenosine Tri Phosphate).
• Hence Mitochondria is called as Power house of cell.  

5) Golgi Bodies: 

• It was discovered by => Camillo Golgi (in 1898).
• It is also called as Golgi apparatus.
• It is made up of group of tubes and vesicles.
• In plant it is more in number and here it is known as Dictyosomes.

Function:

• It work as storage, processing and packaging of material and packages are brought to their destination, hence Golgi apparatus is called as traffic controller of cellular molecules. 
•  It is also involved in synthesis of cell wall, plasma membrane and lysosome.
• It help in the synthesis of carbohydrate from simple sugar which combine with Protein made by Ribosome forming Glycoprotein. 

 
6) Endoplasmic Reticulum:

• It was invented by => Porter (in 1945).
• It membranous network of tubules like structure found in cytoplasm is called Endoplasmic Reticulum.
• It is of two types:
• Rough walled ER: At it ribosome is to be found and it is help in protein synthesis.
• Smooth walled ER: At it ribosome is absent and it is responsible for lipid secretion. In animal cell lipid like steroidal hormones are synthesized by smooth walled ER.

7) Ribosome:

• It was discovered by => G. E. Palade (in 1955).
• It was firstly seen by Calede (in 1941) and called microsome, later it is called ribosome by Palade.
• Diameter of it varies from 150 Å to 250 Å.
• Chemically it is composed of RNA and Protein.
• Eukaryotic ribosomes are 80S  while Prokaryotic ribosomes are 70S. (Here S=> Svedberg Coefficient)

Function:

• It's main function to synthesize the protein, hence Ribosome is called as Factory of Protein. 

8) Lysosome: 

• It was discovered by => De Duve.
• It contain hydrolytic enzyme, which is able to digest every organic substance.
• It help in intracellular digestion that's why Lysosome is called Digestive Vesicle.
• Lysosome is not found in RBC of mammal.

Function:

• It destroy every foreign substance like bacteria etc. inside the cell.
• It replaces old and weak cell organelles, so that new cell organelles originates inside cell.
• If there is need it destroy entire damaged or dead cell, also it destroy itself, hence Lysosome is called as suicide bag of cell.

9) Centrosome:

• It was discovered by => Boveri (in 1888).
• It is only found in animal cell.
• It is not bounded by membrane, it consist of two Centriole.
• Sometimes it is called as diplosome.

Function:

• It help in the cell division and it form spindle fiber between pole during cell division.  

10) Plastid:

•  It is only found in plant cell.
• It's shape is like mitochondria, it has two membrane.
• It is of three types a) Chloroplast b) Chromoplast c) Leucoplast.

a) Chloroplast:

• Found in green colored plant.
• Made up from green colored substance called as Chlorophyll (In Chlorophyll Mg metal is present).
•  By the help of chlorophyll Photosynthesis is done in the presence of sunlight by the plant and trees, thus Chlorophyll is called as Kitchen of the cell.
• Chloroplast is bounded by two membrane having grana and stroma.
•  Grana => It contain chlorophyll molecule and it is a site of light reaction.
•  Stroma => It contain photosynthetic enzyme and it is a site of dark reaction.
• Chloroplast also contain pigments like genthophyll and carotene.
•  The leaf of plant becomes yellow because of formation of carotene.
• Chloroplast also contain double standered  circular DNA molecule and ribosome.
• ribosome in chloroplast is smaller (70S) than cytoplasmic ribosome (80S).

 b) Chromoplast:

• It is colored plastid usually red, yellow or orange color.
• It is found in colored part of plant like flower, fruit, seeds etc.
• Chloroplast are of different kind

1.  Lycopene: In tomato it provide red color.
2. Carotene: Provide yellow or orange color in plant eg:- Carrot
3. Betanin: Found in sugar beet root.

 c) Leucoplast:

• It is colorless plastid.
• It store food in the form of starch, fat and protein.
• It is found in roots and underground stems.
• Amyloplast store starch.
• Elaioplast store oil & fats.
• Aleuroplast store protein.

 

11) Vacuole:

• It is surrounded by semipermeable membrane called as Tonoplast.
• It contains water, sap, excretory product and other material not useful for the cell, means it contain dead organelles of cell.
• In plant it is longer in size & in animal it is smaller in size.

Function:

• It help in osmoregulation & it store toxic metabolic waste.

12) Nucleus:

• It was invented by => Robert Brown (in 1831).
• It is spherical or elliptical.
• It is centrally located major structure found in cell, in plant cell it is shifted towards periphery.
• It control all activity of cell, hence it is called Control Room of cell.
• Components of nucleus:

a) Nuclear membrane:

• It is a double layered membrane.
• It is connected with ER.
• It is made up of protein & fat.
• It has small holes through which cytoplasm & nucleoplasm exchange in cell.

b) Nucleoplasm:

• It is made up from protein, phosphorous & nucleic acid.
• Within nucleoplasm nucleolus and chromatin material is found.

 c) Nucleolus:

• Nucleolus is rich in protein & RNA.
• It synthesize r-RNA & transport it to other place.
• It collect ribosome inside it. 

 d) Chromatin:

• Chromatin is thin thread like structure forming network.
• It is made up of histone protein, DNA & RNA.
• DNA is main component of chromatin which causes genetic character in organism.
• During cell division chromatin breaks into pieces & form Chromosome. 

<Biology Index> 

 

 

Binary Nomenclature of Organism

It became in practice in 1753.

Scientific name has two word-

• First word - Generic name
• Second word - Species name

Organisms	Scientific Name
Man	Homo sapiens
Frog	Rana tigrina
Cat	Felis domestica
Dog	Canis Familaris
Cow	Bos indicus
Housefly	Musca domestica
Mango	Mangifera indica
Rice	Oryza sativa
Wheat	Triticum aestivum
Pea	Pisum sativum
Gram	Cicer artictinum
Mustard	Brassica Campestris

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