COMPOSITION OF BLOOD

GREGOR JOHANN MENDEL (1822 – 1884 ) :

   

Biography:-

·         Johann Mendel was born on 22^nd July 1822 in a village called Heinzendorf.

·         His father was Austrian poor farmer.

·         Mendel’s education began in an upper elementary school in Leopnik, the place about 22 km. away from his village.

·         He was clever and sent to the Traphan high school in 1834.

·         He completed his graduation with good record in 1840.

·         He joined the “philosophical Institute at olmitz in 1843.

·         He joined the university of vienna in 1850.

·         In 1854, he joined the Brun modern school as a teacher and taught mathematics & natural science.

·         He began his famous hybridization experiments on garden pea plant in 1856.

·         He performed experiment on pea plant (Pisum sativum) for 8 years.

·         He presented his work in paper entitled “ Experiments in plant hybridization” at the meeting of the Natural History Society of Brun in 1865

·          He was also published Journal i.e. “Annual proceedings of Natural History Society” in 1866.

·          Unfortunately, his work  remained unknown for 35 years.

·         Mendel died in 1884 he was really respected priest, teacher but nobody could be recognized him as a genius scientist.

Ø  After 35 years in 1900 century his work was rediscovered by three scientist; Hugo De vries from Holland, Karl Correns from Germany & E. Tschermak from Austria independently.

Ø  De vries found research paper of mendel & he published in his flora in 1901.

Ø  During the time of mendel, mitosis & meiosis were not discovered but Hugo De vries’s days mitosis & meiosis were discovered & scientist realized the greatest work of Mendel.

Ø  Based on the  data of Mendel, Corren scientist from Germany postulated three laws of inheritance are known as Mendel law’s of inheritance and new branch of biology i.e. genetics came in biological science.

Mendel’s Experiments:

                Selection of material :

            Mendel selected garden pea plant for  his experimental material. Mendel selected pea plant for his experiment material because of following reasons or characteristics.

1.       Pea plant is small, annual.

2.       Life  spane is short. 

3.       Life cycle completed within 3 to 4 months.

4.       Mendel could grow three generations in a year.

5.       Garden pea plant produces many seeds.

6.        Pea plant is bisexual so easily self pollinated.

7. Plant is small so it requires small area.

8.       Pea plant having several pairs of contrasting characters; like  Tall and Dwarf plant, colored(red) flower & white flower, Yellow & green seeds, Round & wrinkled shape of seed, pod colour is green & yellow, pod shape and flower position.

In this way Mendel had selected 7 pairs of Contrasting /opposite characters.

[Note:  Mendel considered those characters are much more commonly express in plant known as dominant characters & those are not commonly found or express called them recessive characters.]

GENETIC TERMINOLOGY :

Ø  Emasculation :- Removal of anther before anthesis.

Ø  Character :-  It is the feature of an  organism. eg. height of  stem.

Ø  Trait :-  An inherited character which is noticable eg. Tall & dwarf.

Ø  Factor : It is the unit of heredity or particle present on the chromosome responsible for inheritance & expression of particular character.

Ø  Factor term is coined by Mendel. These factors transmit from one generation to another generation and determined the particular character.

Ø  Gene:- It is the segment of DNA which is responsible for inheritance & expression of a particular characters. The term gene is used by Johannsen.

Ø  Alleles & Allelomorphs:- It is the two or more alternative forms of gene (factor) are called alleles. The term alleles were coined by Bateson.

Ø  Dominant :-  It is an allele or gene which expresses its trait either in  presence of alternative allele or even if it is present alone. Eg.  Tt = Tall or TT Tall.

Ø  Recessive :-  It is an allele or gene which is not expresses its trait if it is present in single form or in presence of alternative allele. It can only express its trait in homozygous recessive condition Eg. tt for Dwarfness.

Ø  Phenotype :- The external appearance of an individual for any trait is called phenotype for that trait Eg. trait like Tall or Dwarf for the plant.

Ø  Genotype :- Genetic constitution of an individual with respect to single character or set of characters. If the genotype of  plant for set of characters like Tall plant with yellow seed and Dwarf plant with green seed will be TT YY (homozygous dominant) Tt Yy (heterozygous or Dihybrid ) and Dwarf plant with green seed having (ttyy) genotype.

Ø  Homozygous :- An individual possessing similar alleles for particular trait is called as homozygous condition eg. TT = Tall plant or tt = Dwarf plant. Homozygotic plant producess only one type of gamete.

Ø  Heterzygous : An individual possessing dissimilar alledels for particular trait is called as heterozygous condition or called hybrid for that trait. eg. Tt ( hybrid) Heterozygotic plant or hybrid plant producess two type of gametes.

Ø  Pure line :- It is an individual or group of individuals which are homozygous or true breeding for perticular trait.

Ø  Hybrid :- It is heterozygous individual produced from pure line parents having one or more contrasting traits.

Ø  Monohybrid: A hybrid produced from monohybrid cross is called as monohybrid eg. Tt (monohybrid)

Ø  Dihybrid :- A hybrid produced from dihybrid cross is called as dihybrid eg. TyRr (Tall plant and round seed).

Ø  F1 Generation :- (F stands for filial meaning offspring produced in sexual reproduction)

 (In Latin word fillin means a son) Individual produced from parental generation called  generation.

Ø  P1 parantal generation :- Plants are used for crossing which are true breeding ie. Pure line called as P generation.

Ø  F2 generation :- Progeny or individuals produced from  generation called as progeny and generation called as  generation.

Ø  Punnett square / checker board:-  It is the board like diagram used for showing possibilities of zygotic combination of a particular cross. This board is called as punnett square because Punnett scientist had made this board.

Ø  Homologous chromosomes:- It is the pair of chromosomes which are morphologically and structurally same & present in diploid cell. Such type of chromosomes are called as homologous chromosomes or homologues.

Procedure of experiment:-

1.   Mendel had a systematic approach in his hybridization experiment.
2. He was very methodical. He first studied inheritance of just one trait at a time.
3. Initially he carried out monohybridization considering a single pair of contrasting character.
4. After completing the monohybridization he carried out dihybridization & trihybridization by considering two & three pairs of contrasting characters respectively.
5. Mendel carefully compile the data obtained from hybridization experiments & was able to derive single ratio such as 3:1, 1:2:1, 9:3:3:1, 1:1 for his experiment.

·         Mendel experiment involves three steps-

o   Step 1-Selection of parents and obtaining pure line:

1.       Mendel himself ensured that the selected male & female parent plants are truly breeding or not.

2.       Parent  plant then selected as a parent plant ensures for three generation by selfing.

o   Step 2-Artificial cross of selected parents to raise  generation :

1.       Mendel first emasculated the flower for artificial cross.

2.       He selected as a female parent of those plants whose stamen are removed with the help of forceps.

The shape of carolla of pea plant is papilinaceous type having five petals. one large standard, two are wings at middle & inner two petals are joinet called  carina/ keel. In pea plant stamens are
( 9) +1 condition it can be easily removed.

o   Step 3–Selfing of - hybrids to raise  - generation:

Mendel allowed the natural self pollination of  progeny to get progeny.