Download Gregor Mendel “The Father of Genetics”

Gregor Mendel
“The Father of Genetics”
Chapter 10, Sections 1 and 2
Gregor Mendel (1822-1884)
 An Austrian monk who used a scientific approach to
study inheritance, giving birth to GENETICS (the study
of heredity)
 There was no knowledge of genes or DNA at the time;
Therefore, Mendel’s refers to “factors” (today called
genes)
 His success, in part, came from his choice to use pea
plants in his study
 Contrasting traits or characteristics
 Reproduce sexually, quickly, and have many offspring
 Accessible and easy to handle
Controlled Reproduction
Stamen(♂) produces
pollen
Carpel(♀) produces
ovules (eggs)
Removing immature
stamen prevents
self-fertilization
Mendel’s 7 Traits of Pea Plants
In The Garden…
 Mendel identified stocks of plants that were
TRUE-BREEDING for a particular trait
Tall Plant  self-fertilization  All Tall Offspring
 Mendel cross-fertilized two true-breeding
plants with contrasting characteristics
(ex: purple flowers and white flowers)
 He called them the P generation (for Parental)
What do you think the offspring looked like?
Mendel’s F1 Generation
F1 (for Filial) or “son” in Latin!
The offspring were
100% Purple Flowering
Mendel repeated this
experiment and observed
similar results with all 7 of
the traits he studied!
He called the F1 generation
HYBRIDS
A Second Generation
 Mendel let the F1 generation self-fertilize
and created a F2 generation
The white-flowering trait reappeared in the
2nd Generation!!
(3 Purple to 1 White)
Mendel’s Principles
(in modern
terms)
1.
2.
3.
4.
There are different forms of genes called alleles
Ex: Gene: height
Alleles: tall, dwarf
Genes are inherited in pairs, one allele from each
parent
Homozygous: identical alleles
Heterozygous: different alleles
In a hybrid, only the dominant allele (T) will be
expressed (or seen). The other allele is recessive (t).
Alleles segregate (separate) from each other during
gamete formation and rejoin during fertilization to
make the offspring
Principle of Segregation
What process segregates the alleles during
gamete formation???
MEIOSIS!!
Punnett Squares
 A diagram that can be used to show the
potential outcome of a genetic cross
Genotype and Phenotype
 Organisms with the same PHENOTYPE (physical appearance) may
not have the same GENOTYPE (genetic make-up)
Purple Flowers (PP)
Purple Flowers (Pp)
How do you determine the genotype of an organism with a dominant
trait?
Test Cross
 Cross the dominant (unknown genotype)
with the recessive (known genotype)
50% Green
50% Yellow
100% Green
Mendel’s Principle of
Independent Assortment
 Mendel also looked at two-factor crosses
or DIHYBRID crosses
 Traits sort independently from one
another during gamete formation
Mendel’s F1 and F2
Two-Factor Cross