Genetics-History-Mendel | Notes-by-UK-Sir | Genetics-1
Genetics (Heredity and variation )
 |
| Chromosome |
Genetics:
Definition:
-
The
study of heredity and variation may be called as Genetics.
-
Or
-
The branch of science deals with the study of Heredity and variation may be called as
Genetics.
- or
The detail study of all aspects of gene like structure,
composition, transformation, function and behavior.
-
Genetics
term was introduced by Bateson (1905)
-
Heredity
– transfer of character from parent to off springs ( transformation of gene
from one generation to another cause similarity )
-
Variation-
The dissimilarity (different character)
between parent and off springs.
Branches of Genetics
-
1)Classical
genetics
-
2)Molecular
genetics
-
3)Evolutionary
genetics
-
4)Applied
genetics
History:
-
Hippocrates
– 1st time called reproductive material as “Gonos” (means seeds)
-
Koelreuter
(1760)- 1st time carried out breeding experiment in tobacco plant.
-
T.A.
Knight (1790 )- Crossed two varieties of
garden Pea plant and concluded that some characters are more numerous then
others.
-
John
Goss- (1822) – crossed pea plants and found that a parental character reappears
in off springs.
-
Charles
Darwin (1868)- there are microscopic granules pass directly to the off springs
from parent cell – named as Gemmule.
-
Gregor johann Mendel (1865-66)- 1st time explained details of genetics.
(Called as father of genetics)
 |
| T.H. Morgan |
-
T.H. Morgan (1910)- genes reside on specific chromosomes. Genes occupy specific locations on the
chromosome.
Hugo de Vries (Holland)- He republished Mendel's results in 1901 in Flora magazine
-
W.
Bateson- Father of Modern Genetics
-
Morgan
– Father of Experimental genetics
-
A.
Garrod – Father of Biochemical and Human genetics.
Terminology:
Factor
: or gene
- The entity responsible for inheritance of character or trait. Or inherited factor which determine the biological character of an organism.
Also Named as Unit factor by Mendel.
-
The basic unit of
inheritance of character.
Genes:
- (Molecular biology) Functional part of DNA.
Alleles:
-
Alternative form
of same gene for contrasting characters, located on same position (Locus) on
homologous chromosome. (Tall vs dwarf) Term given by Bateson.
Contrasting
Character:
-
Remarkable /
observable feature for phenotype/ character which can show clear cut difference
(Red vs white)
Phenotype:
-
Physical or
external- observed or appeared character (traits)
-
Ex- Tall, dwarf,
Red, white etc. Phenotype and genotype term was given by Johannsen (1909).
Genotype:
-
Genetic expression
of a character in term of alleles with a symbol (e.g – TT, RR, Tt, Rr, rr etc)
Phenocopy :
It’s a variation of Phenotype. If different Genotype
placed in different environmental conditions, they produce same phenotype.
Which can be called as Phenocopy.
Dominant
: (T, R, W etc)
-
The character/
allele express itself fully/ completely. Denoted by Capital letter. It can
express itself in both homozygous and heterozygous condition.
Recessive
: (t, r, w etc)
-
The character /
allele is suppressed and can’t express itself in single condition. It can only
expressed in homozygous condition.
Wild
allele :
The dominant allele originally present in Population.
Homozygous
condition : (TT, tt, RR etc)
-
Similar alleles
present on corresponding locus of Homologous chromosome.
Heterozygous
condition : (Tt, Rr, Ww etc)
-
Dissimilar
alleles present on corresponding locus of homozygous chromosome.
Hemizygous:
-
If only one gene
of a pair is present, Its called hemizygous condition. (Male individual – hemizygous for sex linked
gene XY)
Gamete
:
-
Haploid (n) Sex
cells (e.g- sperm / egg)
Pure
line :
-
If only one type
of pure offspring present.
Parent
: mating generation
Off
spring : next generation of parent
F1
generation - First generation of
offspring / 1st Filial Generation. (Bateson 1905)
Wild
/pure – With original genotype and
phenotype
Hybrid
/ recombinant – With mixed genotype and phenotype.
Hybrid
Vigour or Heterosis:
-
The superior
hybrid individual over either of its parent (in any trait/ traits).
Inbreeding
:
When the
individuals of a progeny (e.g. F1 generation) are allowed to cross with each
other, it is called inbreeding.
Monohybrid
cross :
The cross
between two parents differing in a single pair of contrasting characters is called
monohybrid cross and the F1 offspring as the hybrid.
Monohybrid ratio :
The phenotypic ratio of 3 dominants : 1 recessive
obtained in the F2 generation from the monohybrid cross is called monohybrid
ratio.
Dihybrid
cross :
The cross between two parents in which two pairs of contrasting
characters are studied simultaneously.
Poly
Hybrid cross:
Involvement
of more than 2 allelic pairs (contrasting characters).
Back
Cross :
The
cross of an individual with any of its parent (Previous generation).
Out
Cross :
When F1 offspring (heterozygous) crossed with
Dominant parent.
Test
cross :
The
cross of F1 offspring (Heterozygous having dominant genotype) with its recessive parent.
Reciprocal
Cross:
A cross in which 2 parents are same , but in one
experiment X can be used as male and Y as female, in another experiment Y as
male and X as female.
Punnett
Square :
A
checker board invented by- RC Punnett to show the result of a cross between two
individual. Male gametes lie horizontally and female gametes lie vertically.
Gene
Pool :
Sum
total of all genotype of all organisms, in a population.
Gregor Johann Mendel ( Father of Genetics)
Name: Johann Mendel
 |
| Mendel |
Born:
July 20, 1822
Died:
January 6, 1884
Education:
University of Olomouc, University of Vienna
Gregor Mendel, is the "father of genetics,"
was born in Austria in 1822. Mendel (was a monk) discovered - basic principles
of heredity through experiments. (in monastery's garden - the inheritance of
certain traits/ characters in pea plants follows particular patterns )
Mendel was born on July 20,
1822 was in Heinzendorf, Austria. He sent to school in Troppau to continue his
secondary education at the Age 11. In 1840, he graduated from the school with
honors.
After graduation, A two-year program at the
Philosophical Institute of the University of Olmütz. in the subjects of physics
and math. Mendel graduated in 1843.
That same year, Mendel began studying to be a
monk: He joined the St. Thomas Monastery in Brno, ( given the name Gregor).
In 1851, he went to the University of Vienna,
to continue his studies in the sciences. Mendel studied mathematics and physics
under Christian Doppler, studied botany under Franz Unger,
In 1853, after completing his studies at the
University of Vienna, Mendel returned to the monastery in Brno - took a teaching
position at a secondary school.
Experiments :
Around 1854, Mendel began his research. Mendel’s research
continued over as many as eight years (between 1856 and 1863). It was involved
tens of thousands of individual plants.
-
Mendel chose to peas for his experiments for many distinct
varieties, and because offspring could be quickly and easily produced.
-
Then cross-fertilized pea plants of opposite
characteristics—tall with short, smooth with wrinkled,
-
Then he put forth the theory that all living things have
traits and factor.
In 1865, Mendel delivered - his findings to the Natural
Science Society in Brno, the results of his studies published in their journal - " Experiments on Plant Hybrids". (same year)
But Mendel’s work was ignored. Mendel did little to
promote his work.
Mendel's finding was not accepted as being generally
applicable.
Later Life and Death:
In 1868, Mendel taught for 14 years, and gradually failing
eyesight. Gregor Mendel died on January 6, 1884, at the age of 61. Mendel’s research
remains buried to decade. His 8 years (1856- 1865) of experimental knowledge
remain unknown to the world.
1900: Rediscovery :
- De Vries, Correns and Tschermak independently rediscover Mendel's work.
-
3 botanists - Hugo De Vries, Carl Correns and Erich vonTschermak - independently rediscovered Mendel's work in the same year (1900).
-
The three Europeans were unknown to each other.
-
They were working on different plant hybrids and the laws of
inheritance.
-
When they reviewed
the literature before publishing their own results, find Mendel's old papers.
By 1900, people were sufficiently understood to give
Mendel's abstract ideas as a physical context. He was awarded as “Father of Genetics”.
Want to get CHSE Biology syllabus (Full version), click the link below:
https://uksirnotes.blogspot.com/2021/06/chse-biology-syllabus-uksir.html
No comments