2. GENETICS:
The term genetics was coined by
Bateson (1906)
The study of heredity and
variations is called as genetics.
“Gregor Johann Mendel” is called
as “ father of genetics”.
3. HEREDITY:
Heredity is a transfer of
characters from parents to
offspring from one generation
to the next generation.
4. VARIATION:
Variation is a degree of difference found in morphological,
Physiological and other traits found among individuals of same
species.
5. VARIATION:
Variations are caused due to the error during DNA
replication.
variations are very less in asexually reproducing organisms
abundant in sexually reproducing organisms.
9. SOMATIC VARIATION:
Also called as acquired variation.
It affects the somatic cells of an organism.
These are not inherited from parents nor transmitted to next
generation.
These variations are acquired by individual during its own
life and lost it with death.
10. GERMINAL VARIATION:
It affects the germinal or reproductive cells.
These are important source of genetic variation in natural
population which lead to evolutionary change.
These are passed on to later generations.
11. ACCUMULATION OF VARIATION
DURING REPRODUCTION:
variation appear during reproduction whether organisms are
multiplying sexually or asexually.
Each generation provides the next generation with a common basic
body design and some subtle variations.
The variations accumulate and pass on to more and more
individuals with each generations.
13. SIGNIFICANCE OF
VARIATIONS:
Preadaptation's- some of the variations function as
preadaptation to changing environment.
For ex; heat wave may kill most bacteria except a few which
have a preadaptation or variation to tolerate high temperature.
14. SIGNIFICANCE OF
VARIATIONS:
Evolution- variations are raw materials for evolutionary
process.
Struggle for existence- useful variation provide advantage to
the individuals in the struggle for existence and hence survival
in nature.
Individuality- variations provides a distinct identity to each
and every individual.
15. SIGNIFICANCE OF
VARIATIONS:
Artificial selection- picking up of certain variations by
breeders have resulted in development of a number of breeds
and varieties of domesticated plants and animals.
16. INHERITED TRAITS:
the caracteristics that are
passed from parents to their
children are called inherited
traits.
heridity is also called as
inheritance /biological
inheritance.
17. INHERITED TRAITS IN HUMAN
BEINGS:
tongue rolling, shape of nose,
earlobe attachment,
dimples,
curly hair, colour of eye,
hairline shape, height, colour complexion, etc....
18. TYPES OF TRAITS:
Dominant trait- the trait which appear in first
generation is called dominant trait. It is denoted by
capital letter. Eg; TT- tall
Recessive trait- the trait which do not appear in
first generation is called recessive trait. It is
denoted by small letter. Eg; tt- dwarf
19.
20.
21. GREGOR JOHANN MENDEL
(1822-1884)
mendel was ws born on 22
july 1822 in Austria.
in 1856-57, he started his
historical experiment of heridity
on pea plant.
22. after 16 years of mendels death in 1900
Mendels postulates was rediscovered.
mendels experiment remains hidden for 34
years.
mendel worked on the rules of
inheritance.
he selected garden pea for the experiment.
GREGOR JOHANN MENDEL
(1822-1884)
23. WHY DID MENDEL SELECTED
PEA PLANT FOR HIS
EXPERIMENT?
these plants are easy to grow in the garden.
the flowers of pea plants are hermaphrodite-
bisexual.
they are self pollinating, so self and cross
pollination c be easily performed.
24. the different physical characters are easy to recognize and study.
they have shorter life span, many offspring can be produced in one cross.
they have good resistance against diseases.
27. LAW OF DOMINANCE.
law of dominance is also called as first law of inheritance.
when parents with pure, contrasting traits are crossed together,
only one trait appears in the next generation.
31. TERMS TO REMEMBER:
Gene- it is a heredity unit which
carries character from one generation
to another generation.
Allele- term allele refers to each of
the members of a genetic pair or
alternate trait of a gene pair.
32.
33. TERMS TO REMEMBER:
Homozygous traits- they have similar
alleles for specific trait ( TT or tt ). They
produce only one kind of gametes.
Heterozygous traits- they have dissimilar
alleles for a specific traits (Tt) . They
produce two types of gametes.
34.
35. LAW OF SEGREGATION:
“ during the formation of
gamete, each gene seperates
from each other so that each
gamete carries only one allele
for each gene”
36. LAW OF INDEPENDENT
ASSORTMENT.
“ the alleles of different genes ae inherited independently within
the organisms that reproduce sexually”
37.
38.
39. IMPORTANT POINTS TO
REMEMBER:
phenotypic ratio of monohybrid cross- 3:1
genotypic ratio of monohybrid cross- 1:2:1
phenotypic ratio of dihybrid cross- 9:3:3:1
genotypic ratio of dihybrid cross- 1:2:1:2:4:1:2:1
40. SEX DETERMINATION IN
ANIMALS:
In some animals sex is determined by the
environment:
Ex;1-> In turtle (chrysema picta), females are
formed if the eggs are incubated at temperature 33
degree celsius, a temperature below 28 degree
celsium forms male turtles.
43. snails called slipper limpets
begin life as males and become
females as they grow.
SEX DETERMINATION IN
ANIMALS:
44.
45. SEX DETERMINATION IN
HUMAN BEINGS:
genetic control of sex determination is carried out
by chromosomes, there are 2 kinds of chromosomes,
allosomes- 1 pair of chromosomes which
determines sex.
autosomes- 22 pairs, any chromosomes apart from
sex chromosomes.
47. SEX DETERMINATION IN
HUMAN BEINGS:
a male has one ‘X’ chromosomes and one ‘Y’ chromosome.
a female has 2 ‘X’ chromosomes.
if the sperm carrying ‘X’ chromosome fertilises an ovum which
carries ‘X’ chromosome, then the child born will be girl.
48. SEX DETERMINATION IN
HUMAN BEINGS:
if the sperm carrying ‘Y’ chromosome
fertilises an ovum which carries ‘X’
chromosome, then the child born will be
boy.
thus the sperm determines the sex of
the child.
