Introduction
to Genetics
1822 - 1889 Austrian Monk
Gregor Mendel
1856 - 1865 Mendel’s Garden at
the Monastery
experiments
with pea plants
Living organisms inherit characteristics from their _____________
Mendel is considered the Father of _______________ - the
study of Heredity
parents
Genetics
Fertilization - the combining of a sperm with an egg
the result is called a zygote
Fertilization
Male and female reproductive cells join
Sex Cells (Gametes)
egg (ovum - animals) (ovule –
plants)
sperm (pollen – plants)
Fertilization by Pollination
Pea plants self-pollinate – the pollen of a plant
can form a zygote with the egg of the same plant
Mendel used cross-pollination – the pollen from
the stamen of one plant was transferred to the
egg in the pistil of a different plant using a
paintbrush
True-breeding means that all offspring will have the form of the
trait that the parents have.
Before starting his experiments, Mendel wanted to make
sure the original parents were “true-breeding” or “pure” for
the trait being studied.
If these parents are “pure” for seed color:
all these offspring will have
yellow seeds
all these offspring will have
green seeds
but, his first experiments studied only one trait at a time.
Mendel studied 7 different traits of the common garden pea plant
smooth vs. wrinkled seeds
green vs. yellow seeds
smooth vs. wrinkled seed pods
green vs. yellow seed pods
purple vs. white flowers
axial vs. terminal flower position
tall vs. short plants
Trait – a specific _____________ characteristic
Each trait had ________ different forms (round or wrinkled shaped)
inherited
two
Mendel’s First Crosses P generation = original parents
F1 generation = first generation = 1st “Filial” (means sons
or daughters)
All offspring (F1) were hybrids, each showing
characteristics of only one parent
_________ - offspring between parents different for a certain trait Hybrid
Mendel’s Conclusions
1 1. Principal of Unit Factors - offspring receive ___ unit factor
from each parent for a trait
2. Principal of ____________- some factors are dominant (always
appear) and some are recessive (masked out by the dominant
factor)
Dominance
What We Know Today of Mendel’s Conclusions
genes Mendel’s Factors were _________ located on chromosomes
factor
Chromosome
Gene
alleles Different
An organism with a dominant allele will exhibit that form of the
trait
An organism with a recessive allele will exhibit it only if a
dominant allele is ________ present not
Mendel’s First Results
Used parents that were true-breeding, such as tall x short
dominant
•100% offspring were tall
•“tall” factor was ___________ over “short” factor
Review of Generations
1st set of
offspring
(F1
generation)
original
parents
(P generation)
2nd set of
offspring
(F2
generation)
Mendel called the parents for an experiment the P generation.
Mendel called the first generation of offspring the F1 generation.
Mendel called the second generation of offspring the F2 generation
(2nd “filial” generation).
Law of Segregation
dominant
• Mendel continued by crossing
the F1 offspring to produce the
F2 generation
• All F1 generation were _______ hybrids
• Result of the F1 generation
cross producing the F2
generation:
•___% of offspring were
dominant (tall)
•___% of offspring were
recessive (short)
75
25
Mendel’s Conclusions of the F1 Cross 2 1. Each parent had ___ factors for each trait (one from each of
its parents
2. Each parent had a dominant and a _____________ factor
• only way an F2 offspring could
end up with recessive trait
recessive
separate 3. 2 factors had to __________ when
sex cells (gametes) formed
• otherwise, offspring would always
get a dominant factor & have the
dominant trait
Law of ______________- two
alleles must separate
when gametes form
Segregation
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