2. CONTENTS
• INTRODUCTION.
• MENDEL’S WORK.
• MENDEL’S LAWS OF INHERITANCE.
• DEVIATIONS FROM MENDELISM.
• SEX LINKED INHERITANCE WITH
EXAMPLE OF DROSOPHILA .
3. • Genetics is a field of biology that studies how traits
are passed from parents to their offspring.
• The passing of traits from parents to offspring is
known as heredity aka inheritance.
GENETIC INHERITANCE
Sexually
reproducing
organisms.
Asexually
reproducing
organisms.
4. • Gregor Johann Mendel – Father of Genetics.
• For six years he worked on Pisum sativum.
MENDEL’S EXPERIMENTAL MATERIAL
Mendel selected Pisum sativum i.e. pea
plant as his experimental material
because:-
1. Presence of contrasting traits.
2. Life span is short.
3. Pea plant is self-pollinated but can be
cross pollinated easily.
4. Doesn’t require more maintenance.
5. Seeds don’t show dormancy.
6. By using this, can do a huge sample
study in short period of time.
6. • Characters are
controlled by alleles
or factors which
occur in pairs.
• When two
contrasting traits are
present only one
factor will express
itself in F1
generation.
7. • Aka Law of purity of gametes.
• Factors present in pairs segregate from each other during
gamete formation.
• They don’t show any blending or mixing.
8. • It is based on di-hybrid
cross.
• When two contrasting
characters are combined
in a hybrid, segregation
of one pair of character is
independent of another
pair of characters.
• In simple words,
Inheritance of one
character doesn’t affect
inheritance of another.
• Both characters assort
independently.
9. • F1 generation shows
characters intermediate to
the parental genes.
• Dominant gene is unable
to completely dominant
over recessive gene.
• Examples:
1) Mirabilis jalapa
2) Antirrhinum majus
3) Andalusian fowl
10. • Phenomenon in which two alleles
are able to express themselves
when present together.
• Both alleles are dominant.
• Example:
1. AB Blood grouping,
2. Coat color in cattle.
11. • The characters which are controlled
by the sex linked genes are termed
as sex linked characters.
• Females generally function as
carriers of sex-linked disorders.
• The sex linkage was first discovered
by T.H Morgan in 1910 in the
Drosophila melanogaster.
• Its eye color is sex linked.
• White eyed male Drosophila
melanogaster was mated with red
eyed female Drosophila
melanogaster.
• On self cross, F2 generation
consisted of red eyed female
population and male population with
50% red eyed population and 50%
with white eyed.
• It is a criss-cross inheritance.
