Download 6.3 Mendel and Heredity

6.3 Mendel and Heredity
KEY CONCEPT
Mendel’s research showed that traits are inherited as
discrete units.
6.3 Mendel and Heredity
Genetics: is the study of biological inheritance patterns and
variation in organisms.
The groundwork for much of our understanding was laid down
in the middle of the 1800s by Gregor Mendel.
“Father
of
Genetics”
6.3 Mendel and Heredity
When we think of how offspring resemble or differ
from their parents, we refer to specific traits.
Traits: are
distinguishing
characteristics that
are inherited.
Ex: eye color, leaf
shape, tail length
6.3 Mendel and Heredity
Many people thought that traits were blended.
•As in your traits were a perfect mixture
of your mother’s and father’s traits.
6.3 Mendel and Heredity
But this failed to explain how certain traits remained with
out being “diluted”
6.3 Mendel and Heredity
Mendel’s data revealed patterns of inheritance.
• Mendel made three key decisions in his experiments.
– use of purebred plants
– control over breeding
– observation of seven
“either-or” traits
Purebred: genetically uniform
6.3 Mendel and Heredity
Either/Or traits
•
•
•
•
•
•
•
Pea shape: round OR wrinkled
Pea color: green OR yellow
Pod shape: smooth OR constricted
Pod color: green OR yellow
Plant height: tall OR short
Flower color: purple OR white
Flower position: axial OR terminal
6.3 Mendel and Heredity
• Mendel used pollen to fertilize selected pea plants.
– interrupted the self-pollination process by removing male
flower parts
Mendel controlled the
fertilization of his pea plants
by removing the male parts,
or stamens.
He then fertilized the female
part, or pistil, with pollen from
a different pea plant.
6.3 Mendel and Heredity
What did Mendel find in his first Generation (F1)
P
p
p
Genotype:
Phenotype:
P
6.3 Mendel and Heredity
What did Mendel find in his first Generation (F1)
P
p
Pp
p
Pp
P
Pp
Pp
Genotype: Pp
Phenotype: 100% Purple Flowers
6.3 Mendel and Heredity
What did Mendel find in his second Generation (F2)
P
P
p
Genotype:
Phenotype:
p
6.3 Mendel and Heredity
What did Mendel find in his second Generation (F2)
P
p
P
PP
Pp
p
Pp
pp
Genotype: PP, Pp, pp
Phenotype:75% Purple flowers, 25% white flowers
6.3 Mendel and Heredity
• Mendel allowed the resulting plants to self-pollinate.
P
F1
F2
– Plants in generation 1 (F1) were all purple
– Most plants ( ¾ )in generation 2 (F2) were purple, but
white began to appear in some offspring (¼ )
6.3 Mendel and Heredity
• Mendel observed patterns in the first and second
generations of his crosses.
6.3 Mendel and Heredity
• Mendel drew three important conclusions.
1. Traits are inherited as discrete units/
individually. (genes)
purple
LAW OF SEGREGATION
2. Organisms inherit two copies of each
gene, one from each parent.
3. The two copies separate
during gamete formation (Meiosis).
white