Section 6-3
“Mendel”
Write everything that is
underlined
6.3 Mendel and Heredity
KEY CONCEPT
Traits (characteristics) are inherited as
discrete (separate) units
6.3 Mendel and Heredity
Before we begin…
• Sit quietly for 30 seconds as you THINK!!!!
• Think about this…
– What are some traits you have that make you look
like your mom or dad? If you don’t know what your
mom or dad looks like, what are some qualities
that make you look unique from the rest of your
family? Or do you look more like one parent than
another?
– Why do you think this is???
6.3 Mendel and Heredity
Key Vocabulary Terms
• Traits are distinguishing
characteristics that are inherited
(like hair color or blood type)
• Genetics is the study of
biological inheritance patterns
and variation
• Heredity: The passing of traits
from parents to offspring
6.3 Mendel and Heredity
Background Information
• In the 1800s, Gregor Mendel
(an Austrian monk) made
the first studies in
predicting how traits would
transfer from one
generation to another
• Many in Mendel’s day
thought traits were
blended …. A red flower
and a white flower would
make a pink flower
A. Mendel studied pea plants for 3 main
reasons:
1. All the traits came in 2 easy to recognize
forms
2. Both male and female gametes (sex
cells) are produced on the same plant
3. The reproductive parts are tightly
enclosed in petals preventing pollen
from other plants entering
6.3 Mendel and Heredity
B. Fertilization
• The uniting of male and
female gametes (sex cells)
– Plants “pollinate”
1.A hybrid plant would
have one of each form
of a trait
6.3 Mendel and Heredity
Think for a minute…- then pair/share
• Have you ever heard of the term hybrid before????
• Def: the offspring of two animals or plants of different
breeds, varieties, species, or genera, esp. as produced
through human manipulation for specific genetic
characteristics
• Can you think of any examples of hybrids?
• Livestock examples– Yorkshire Pig x Hampshire Pig= Blue Butt
– Black Angus x Hereford= Black Baldy
– Thoroughbred x Arabian= Anglo Arabian
6.3 Mendel and Heredity
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
B. Mendel’s 1st Experiments
st
1
1.Mendel’s
Experiments
were called Monohybrid
crosses (the plants were
different by just one trait)
• Example: all pea plants had
purple flowers and green seeds,
but some are tall and some short
6.3 Mendel and Heredity
B. Mendel’s 1st Generation
1. He crossed a pea plant that was pure
purple flowers (it had only purple
genes) with a plant that was pure for
white (only white genes)
2. The offspring were all purple, no
white pea flowers grew
3.The white trait seemed to
disappear
6.3 Mendel and Heredity
6.3 Mendel and Heredity
C. Mendel’s 2nd Generation
1.Mendel crossed two of the
offspring from the 1st
generation
2.His results were 3 of every 4
plants were purple and 1 in 4
was white
3.The white trait reappeared
6.3 Mendel and Heredity
6.3 Mendel and Heredity
3. Abbreviations
1. P1 = parent in the 1st generation
2. The offspring of P1 were called the
F1 generation
– “F” stands for filial
– Filial stands for son or daughter
3. The offspring of the cross between
2 F1 plants were called the F2
generation
6.3 Mendel and Heredity
• What disappeared in the
st
1 generation?
• The trait for white
• What reappeared in the
nd
2 generation?
• The trait for white
6.3 Mendel and Heredity
• Mendel observed patterns in the first
and second generations of his crosses
6.3 Mendel and Heredity
D. Mendel’s Conclusions
1. Mendel concluded that each organism has
2 factors that control each of its traits
2.The factors controlling traits are
called genes
3.One comes from each parent
4.They are found on the
chromosomes
5.Genes exist in alternative forms
6.3 Mendel and Heredity
E. Law of Segregation:
1.During fertilization, the 2
different genes randomly pair
to produce 4 different
combinations of alleles
2.They separate independently
6.3 Mendel and Heredity
• Draw the next slide – you
will use this on your
genetics book project ****
6.3 Mendel and Heredity
Law of Segregation
Tt
Parents
x
Tt
T T Tt
Tt
Offspring
tt
6.3 Mendel and Heredity
Gregor Mendel is my Hero!!!!!
• http://www.youtube.com/watch?v=8hKBHUaPo3I&saf
ety_mode=true&persist_safety_mode=1
• (Note- you won’t know all of the information on here
yet… but it will soon become clear to you. )
• http://www.youtube.com/watch?v=B1mCwf2ymc&safety_mode=true&persist_safety_mode=1