Download Mendel Word Notes

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11.1 Notes—The Work of Gregor Mendel
I.
Genetics
A. Definition—Scientific study of heredity
B. Heredity
1. Set of traits inherited, or passed down, from generation
to generation
2. It is what makes each species unique
II.
Gregor Mendel
A. Austrian monk considered to be the “Father of Genetics”
B. Experimented with pea plant fertilization (mid 1800’s)
1. Why pea plants?
a. Advantages of using pea plants
i. Contrasting characteristics (tall/short,
green/yellow etc.)
ii. Reproduce sexually
iii. Mendel could CONTROL the crosses
iv. Reproduce quickly (short life cycles)
v. Produce MANY offspring
C. Mendel’s First Experiments
1. Mendel began by studying different traits
a. Examples: green seeds, yellow seeds, pod shape,
flower position etc.
2. He crossed the P (parental) generation and then studied
the offspring.
a. The offspring are found in the F1 generation and
are called hybrids because they are mix of the
parents with different traits.
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3. What Mendel saw:
X
True-breeding tall X true-breeding short
(P generation)
Tall
Tall
(F1 generation)
4. What Mendel Concluded:
a. (1) Biological inheritance is determined by
factors that control traits called genes.
i. Different forms of a gene that code of the
same trait are called alleles
ii. Gene: HeightAlleles: Tall and short
b. (2) Principle of Dominance
i. States: Some alleles are dominant and
others are recessive.
ii. Organisms that carry the dominant allele
will always show the dominant trait.
iii. Organisms will show the recessive trait
ONLY when the dominant allele is not
present.
D. Mendel’s Second Experiments
1. Mendel wondered “What happened to the recessive
allele?”
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2. Mendel, crossed the F1 generation with itself to
produce the F2 generation
3. What Mendel Saw:

X
Tall
X
Tall
Tall
F1 Generation
Tall
Tall
Short
F2 Generation
4. What Mendel Concluded:
a. Law of Segregation:
i.
States: Alleles segregate (separate) form each
other to form gametes (sex cells) that have a
single copy of each gene.
III.
Great Genetic Tips! 
A. Helpful hints…
1. Dominant—allele that is expressed—what you see.
When written in a genetics problem, it is represented by
a capital letter. (Dominant allele = Green = G)
2. Recessive—allele that is only expressed in the absence
of the dominant allele. When written in a genetics
problem, it is represented by a lower case letter…the
same letter as the dominant allele. (Recessive allele =
yellow = g)
3. Alleles are different forms of the SAME GENE!