1. MENDELIAN INHERITANCE
PRESENTED BY :
ANJEEL KUMAR THAKUR
Sr. Lecturer in Botany, Govt. HSS Jhiri, Jammu
DATE : 24TH MAY 2018

2. ANJEEL KUMAR THAKUR
WHAT IS INHERITANCE ?
Transmission of genetic characters ( both resemblances and variations ) from parents to their children ( offspring ) is called INHERITANCE .
Also known as HEREDITY
VARIATION is the differences shown by the individuals of the species and offspring of the same parents
Scientific study of mechanism of inheritance and the causes of hereditary variation in living organisms is called GENETICS
Basic principles of genetics were discovered by
Gregor Johann Mendel ( )

3. Gregor Johann Mendel 1822-1884 Austrian monk
ANJEEL KUMAR THAKUR
Gregor Johann Mendel
Austrian monk
Studied the inheritance of traits in PEA PLANTS
Between he cultivated some pea plants
Developed laws of inheritance
Employed the laws of probability and statistical methods for analysis of his results
Presented his findings in a paper entitled EXPERIMENTS IN PLANT HYBRIDISATION which was read before BRNO NATURAL HISTORY SOCIETY in 1865
Called the Father of Genetics
But his work was not recognized until the turn of 20th century

4. Why did he choose GARDEN PEA ( Pisum sativum ) for experiments ?
ANJEEL KUMAR THAKUR
Why did he choose GARDEN PEA ( Pisum sativum ) for experiments ?
Has a large number of VARIETIES
Is ANNUAL with growth period of few months
Can be grown in a SMALL AREA
Produces a lot of OFFSPRING
Produces pure plants when allowed to SELF-POLLINATE
for several generations
Can be artificially CROSS-POLLINATED
Is small but flowers are large enough to be manually handled
Hybrids are fertile

5. What were the characters of Pea studied by Mendel ?
ANJEEL KUMAR THAKUR
What were the characters of Pea studied by Mendel ?
S.NO.
CHARACTER
DOMINANT TRAIT
RECESSIVE TRAIT 1.
HEIGHT
TALL
DWARF 2.
FLOWER POSITION
AXILLARY
TERMINAL 3.
COLOUR OF UNRIPE POD
GREEN
YELLOW 4.
POD SHAPE
FULL/INFLATED
CONSTRICTED 5.
COLOUR OF FLOWER
COLOURED
WHITE 6.
SEED SHAPE
ROUND
WRINKLED 7.
SEED ( COTYLEDON ) COLOUR

6. ANJEEL KUMAR THAKUR
TERMINOLOGY
TRAIT : Any characteristic which can be passed from parent to offspring
HEREDITY : Passing of trait from parent to offspring
GENETICS : Study of Heredity
Mono hybrid cross : Cross involving a single trait e.g. Height of the plant
Di hybrid cross : Cross involving two traits e.g. Form and colour of the seed

7. TERMINOLOGY Alleles /Allelomorphs : Two forms of a gene
ANJEEL KUMAR THAKUR
TERMINOLOGY
Alleles /Allelomorphs : Two forms of a gene
(dominant and recessive)
Dominant : Stronger of the two genes expressed in the hybrid; represented by CAPITAL letter e.g. ‘T’ for Tallness
Recessive : Gene that shows up less often in a cross; represented by LOWER CASE letter e.g. ‘t’ for Dwarfness
Genotype : Gene combination or genetic make up of a trait (TT, Tt, tt)
Phenotype : Physically expressed feature from a genotype e.g. TALL (TT, Tt) , DWARF (tt) etc.
Homozygous genotype : Gene combination involving two dominant or two recessive genes e.g. ‘TT’ (homozygous or pure dominant) & ‘tt’ (homozygous or pure recessive)
Heterozygous or Hybrid genotype : Gene combination of one dominant and one recessive genes e.g. ‘Tt’

8. ANJEEL KUMAR THAKUR
MENDEL’S EXPERIMENTS WERE GROUPED DEPENDING ON THE NUMBER OF TRAITS TAKEN UNDER CONSIDRATION AT A TIME AS :
CROSS TYPE
NUMBER OF TRAITS UNDER STUDY
MONO HYBRID CROSS
ONE ( e.g. HEIGHT OF THE PLANT )
DI HYBRID CROSS
TWO ( e.g. SHAPE AND COLOUR OF SEEDS )
TRI HYBRID CROSS
THREE ( e.g. HEIGHT OF PLANT, SHAPE AND COLOUR OF SEED
POLY HYBRID CROSS
THREE OR MORE THAN THREE

9. ANJEEL KUMAR THAKUR
MONO HYBRID CROSS

10. ANJEEL KUMAR THAKUR
MONO HYBRID CROSS

11. MONO HYBRID CROSS conclusions
ANJEEL KUMAR THAKUR
MONO HYBRID CROSS conclusions
Each organism has a large number of characters but each character behaves as a unit
(PRINCIPLE OF UNIT CHARACTERS)
Characters are controlled by factors and there is a pair of factors for each character. An individual receives one factor for a trait from each parent and in turn passes at random one of the two factors to each offspring (PRINCIPLE OF PAIRED FACTORS)
Out of the pair of factors only one expresses itself (dominant) while the other remains unexpressed (recessive ) . The latter expresses only in homozygous state
(PRINCIPLE OF DOMINANCE)
The paired factors don’t mix up but remain distinct and segregate at the time of gamete formation so that a gamete receives only one factor of a character and is always pure
(LAW OF SEGREGATION/LAW OF PURITY OF GAMETES) . It has universal acceptance.
F2 PHENOTYPIC RATIO IS 3:1 WITH A HIDDEN RATIO OF 1 PURE DOMINANT, 2 HYBRID AND 1 RECESSIVE

12. ANJEEL KUMAR THAKUR
DI HYBRID CROSS

13. DI HYBRID CROSS conclusions
ANJEEL KUMAR THAKUR
DI HYBRID CROSS conclusions
The two factors of each character assort or separate independent of the factors of other characters at the time of gamete formation and get randomly rearranged in the offspring producing both parental and new combinations of traits.
(LAW OF INDEPENDENT ASSORTMENT)
F2 phenotypic ratio is 9:3:3:1

14. ANJEEL KUMAR THAKUR
BACK CROSS : CROSS BETWEEN F1 HYBRID AND ONE OF THE PARENTS ( PURE DOMINANT OR PURE RECESSIVE )
BACK CROSS INVOLVING PURE RECESSIVE PARENT (TEST CROSS)
BACK CROSS INVOLVING PURE DOMINANT PARENT (OUT CROSS)
TEST CROSS RATIO
TALL : DWARF
1 : 1
Any cross involving a homozygous recessive trait and an unknown genotype ( homozygous dominant or hybrid ) is known as a TEST CROSS

15. Why did Mendel’s work go unnoticed for some 34 years ?
ANJEEL KUMAR THAKUR
Why did Mendel’s work go unnoticed for some 34 years ?
Published his work in an OBSCURE JOURNAL
Failure of the scientists to notice his work because the scientific world was being rocked by Darwin’s theory of Evolution
His ideas were ahead of his time
Mendel’s failure to get the same results in Hawkweed ( Hieracium ) undertaken on the suggestion of Naegeli. It was due to non availability of pure lines
Absence of aggressiveness in Mendel’s personality

16. REDISCOVERY OF MENDEL’S WORK
ANJEEL KUMAR THAKUR
REDISCOVERY OF MENDEL’S WORK
Hugo de Vries of Holland, Carl Correns of Germany and Erich von Tschermak of Austria rediscovered Mendel’s work independently in 1900
Correns raised the status of two Mendel’s generalizations to the level of laws of heredity :
i. LAW OF SEGREGATION ( 1st Law of Mendelism )
ii. LAW OF INDEPENDENT ASSORTMENT
( 2nd Law of Mendelism )
The other principles were called by Correns as VARIABLE PRINCIPLES

17. THANKS
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