Download Gregor Mendel

Gregor Mendel
Intro to Genetics
Gregor Mendel
● Austrian monk & substitute high school
teacher
● In charge of the garden in the monastery
● His experiment (1856-1863) found
patterns in inheritance before the
discovery of genes
● Father of genetics
○ genetics- study of trait inheritance
Mendel’s Experiment
● Used pea plants because they…
○ were easy to control
○ grew quickly
○ had easily observable traits
○ were able to self-pollinate
○ could have male flower parts removed to control fertilization
■ fertilization- the fusion of male and female reproductive
cells
Mendel’s Experiment
● Mendel worked with purebred, or true-breeding, plants
○ if the plant self-pollinated, the offspring would have
identical traits as the parent
● Traits that Mendel observed
○
○
○
○
○ height (short or tall)
pea shape (round or wrinkled)
○ flower color (pink or white)
pea color (green or yellow)
pod shape (smooth or constricted) ○ flower position (axial or
terminal)
pod color (green or yellow)
Mendel’s Experiment
How the Experiment Worked
1. Mendel wanted to breed two pea plants
with a different trait (ex. pink and white
flowers)
○ to prevent self-pollination, Mendel
removed male parts of the flowers and
fertilized plants with a paintbrush
○ This is the parental, or P, generation
How the Experiment Worked
2. The offspring all had purple
flowers
○ hybrid- offspring from parents
with different traits
○ this is the first filial
(son/daughter), or F1,
generation
Mendel’s Conclusions So Far
● Inheritance is determined by factors passed from parents
to offspring; we now know these as genes
● Each trait had two contrasting forms; each gene has two
different forms, called alleles
● Some alleles are dominant, some are recessive
○ an organism with 2 recessive alleles has the recessive trait
○ if 1 dominant allele is present, the organism has the
dominant trait
How the Experiment Worked, part 2
3. Mendel allowed the F1
generation to self-pollinate
4. The offspring of the F1
generation had both purple and
white flowers at a ratio of 3:1
● This is the second filial, or
F2, generation
Mendel’s Conclusions
● The same ratios occurred between
each of the contrasting pairs of traits
● In the F1 generation, the dominant
allele hid the recessive allele
● The gametes of the F1 generation
separated the recessive and
dominant alleles
○ gamete- sex cell (sperm, egg)
Law of Segregation
● Traits are inherited as discrete units (genes) and not
blended
● One allele for each gene is inherited from each parent
● Only one allele of each gene is in an organism’s gametes