Mendel's law of inheritance

1. MENDEL’S PRINCIPLE OF
INHERITANCE

2. PAGE 1
Inheritance in pea plants:
Our knowledge of how inherited traits are being passed from one
generations to another comes from Mendel law’s of inheritance.
Mendel worked on pea plants, but his principles apply to traits in
plants and animals – they can give you reason how we inherit our
eye colour, hair colour and even tongue-rolling ability.
He found approximately 30 traits out which he selected 7 traits. He
chose traits that had 2 forms:
 Pea shape (round or wrinkled)
 Pea colour (yellow or green)
 Flower colour (purple or white)
 Flower position (terminal or axial)
 Plant height (tall or short)
 Pod shape (inflated or constricted)
 Pod colour (yellow or green).
Mendel started with pure breeding pea plants because they always
produced progeny with the identical characteristics as the parent
plant. Mendel cross-bred these pea plants and marked the traits of
their progeny over several generations.
Mendel’s principles of inheritance
Key principles of genetics were developed from Mendel’s studies
on peas.

3. PAGE 2
1. Fundamental theory of heredity:
Inheritance involves the passing of discrete units of inheritance, or
genes, from parents to offspring. He noticed that paired pea traits
were either dominant or recessive. When pure-bred parent plants
were cross-bred, dominant traits were always seen in the progeny,
but recessive traits were hidden until f1 plants were self-pollinated.
Mendel found the number of second-generation (F2) progeny with
dominant or recessive traits and found a 3:1 ratio of dominant to
recessive traits. He concluded that traits were not blended but
remained distinct in subsequent generations.
Mendel didn’t know about genes but he did presume that there
were 2 factors for each basic trait and that 1 factor was inherited
from each parent.
We know that Mendel was talking about genes or more specifically
alleles – different variants of the same gene. In today’s genetic
language, a pure-breeding pea plant line is a homozygote – it has 2
identical copies of the same alleles. An F1 cross-bred pea plant is a
heterozygote – it has 2 different alleles.
Let’s take shape of seed. Take “B” for round seed (dominant)
whereas “b” for wrinkled (recessive). Diagram given below will
help you understand more precisely.