Download 11.1 Mendel File

Ch.11-1
Mendel
POINT > Define heredity and genetics
POINT > Introduce Mendel
POINT > Describe Mendel’s approach to his
experiments
POINT > Relate Mendel’s experiments to
current knowledge
POINT > Define heredity and genetics
Heredity is the transfer of characteristics
from parent to offspring
Genetics is the study of heredity
POINT > Define heredity and genetics
Thinking into the 1800’s: Traits BLENDED between
parents
POINT > Introduce
Mendel
Austrian Monk
High school teacher
Responsible for the monastery garden
Used pea plants to study heredity
POINT > Describe Mendel’s approach to his
experiments
Why were pea plants so useful in these expriments?
1. Easy to grow and grow quickly (reproduction ~ 90
days)
2. Lots of offspring (good for statistical analysis)
3. Easy to control plant mating (self-pollinating)
4. Easily viewed, dichotomous traits!
WB CHECK:
Which is not a reason pea plants were useful to
Mendel?
a) grow quickly
b) self pollinate
c) require very little water
d) have traits that are easy to see
e) easy to control mating
Where did Mendel do his experiments?
POINT > Describe Mendel’s approach to his
Pollen located in the
experiments
anthers of the stamen
Peas have both male (pollen)
& female (ovule/egg)
reproductive parts
Peas often self-pollinate, which
results in purebred offspring:
Genetically identical to parents
Ovule located in the
ovary of the pistil
POINT > Describe Mendel’s approach to his
experiments
Mendel removed the stamen
before self-pollination
This allowed Mendel to
control which plants crossed
with each other (no selfpollination)
POINT > Describe Mendel’s approach to his
experiments
Mendel manually pollinated
each plant
So any variations were due
to his experiments
POINT > Describe Mendel’s approach to his
experiments
A trait is a specific characteristic of an individual
Mendel studied seven observable traits in peas
POINT > Describe Mendel’s approach to his
experiments
Mendel first crossed purebreds that had trait
differences
P
Green
Seed
Yellow
Seed
(Parental)
F1
(First Generation)
?
POINT > Describe Mendel’s approach to his
experiments
Hybrids are offspring that result from
crosses between parents with different traits
POINT > Describe Mendel’s approach to his
experiments
Mendel first crossed purebreds that had trait
differences
P
(Parental)
F1
(First Generation)
All offspring were yellow
This happened with all
of the traits he tested
POINT > Describe Mendel’s approach to his
experiments
Mendel then allowed F1 plants to self-pollinate
F1
(First Generation)
F2
(Second Generation)
?
POINT > Describe Mendel’s approach to his
experiments
Mendel then allowed F1 plants to self-pollinate
F1
(First Generation)
F2
(Second Generation)
POINT > Describe Mendel’s approach to his
experiments
Mendel then allowed F1 plants to self-pollinate
75% Yellow, 25% Green
All the traits he tested had a 3:1 ratio in the F2
F2
(Second Generation)
WB CHECK:
When Mendel crossed purebred plants in the
P generation, what percentage of the F1
offspring had green seeds?
When Mendel crossed F1 plants, what
percentage of the F2 offspring had green
seeds?
POINT > Describe Mendel’s experiments
Another example: cross a purebred purple
flower plant with a purebred white flower plant
POINT > Describe Mendel’s experiments
When Mendel did this cross, purple x white, all of the
offspring had purple flowers.
POINT > Describe Mendel’s experiments
Mendel then let the F1 generation self-pollinate
(F1 x F1)
Remember all these plants had purple flowers
POINT > Describe Mendel’s experiments
25% of the F2 generation were white!
The same was true of the other traits 75% -25%
POINT > Relate Mendel’s experiments to
current knowledge
Genes are factors passed from one generation to the
next that determine an individual’s characteristics
ex. pea color, plant height, etc
POINT > Relate Mendel’s experiments to
current knowledge
Alleles are different forms of a gene that occur at the
same location on a chromosome
One allele is inherited from each parent (two total)
Often, only one allele can be expressed
(Principle of Dominance)
POINT > Relate Mendel’s experiments to
current knowledge
A dominant allele is always expressed
if it is present
ex. Both alleles are dominant
ex. Alleles are different
POINT > Relate Mendel’s experiments to
current knowledge
A recessive allele is only expressed when the
dominant allele is not present
(ex. green seed allele)
POINT > Relate Mendel’s experiments to
current knowledge
Segregation is the separation of alleles during
gamete formation
Meiosis!! When homologous chromosomes
separate, the two sets of alleles are segregated
Evidenced by the reappearance of recessive alleles
in the F2 generation
POINT > Relate Mendel’s experiments to
current knowledge
Mendel deduced that factors (genes) came in pairs,
which were segregated during reproduction
Mendel’s work was published in 1866, but went
unnoticed until many years after his death
The discovery of his work led to the basic principles
of genetics
We will apply Mendel’s principles…
Read 11.1
S.A. #1-2 page 312