FG 1
Fundamentals of Genetics
Enduring Understanding
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Chromosomes contain genes in which heredity information is
stored.
Genetic variation is essential to biodiversity and the stability of a
population.
Genetic variation is the result of the law of segregation and the law
of independent assortment.
One or more genes can determine an inherited trait of an individual
and a single gene can influence more than one trait.
Random mutations in DNA may be caused by the environment and
are another source of genetic variation.
Essential Questions
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What causes different traits throughout different generations of an
organism?
What causes variation within a population?
I. Mendel’s Legacy
*Genetics branch of biology that studies how characteristics are
transmitted from parents to offspring
*Gregor Mendel Austrian monk father of genetics
experimented w/ garden peas
A. GREGOR MENDEL
* Heredity the transmission of characteristics from parents
to offspringused garden peas
*Used math (statistics) and science
1) Mendel’s Garden Peas
a) Traits(characteristics)mendel(7)plant height,
seed color…….
b)Found Variations tall plant seedsgive tall and
short plants
B. MENDEL’S EXPERIMENTS
FG 2
1) Pure(for a trait) then plant always produces that trait
2) Strain plants that are pure for a specific trait
C. MENDEL’S RESULTS AND CONCLUSIONS
1) Recessive and Dominate Traits
a) Dominate allele masks or dominates other alleles
b) Recessive allele trait that does not appear
(masked)(is not seen in phenotype)
2) The Law of Segregation
a) Paired alleles separate during meiosis
b) Gametes only have 1 allele from each pair
c) Gamete + Gamete = fertilized egg(zygote)
(Offspring)2 alleles controlling a specific trait
d) The Law of Segregationa pair of alleles is
segregated (separated) during the formation of
gametes
3) The Law of Independent Assortment
a) Law of Independent Assortment Alleles for
different traits are distributed to gametes
independently (the distribution of one trait does not
influence the distribution of another)
Mendel’s Principles
Unit Characters (Factors)
Every characteristic is controlled by at least two factors, or genes
(alleles), one coming from each parent.
Dominance and Recessiveness
One allele masks the other allele of the pair, preventing it from being
expressed.
Segregation
The two alleles for a trait separate during sperm and egg formation
(meiosis).
FG 3
Independent Assortment
Alleles for different traits are independently distributed to reproductive
cells.
Explanations should include:
Characteristics are caused by genes, which occur in pairs.
 First generation (F1) organisms are all dominant, the recessive trait
shows up in second generation (F2).
 In the formation of a sex cell or gamete, the gene separates or
segregates out independently so that each daughter cell will
contain only one gene from the parent: e.g., in the pea plant gene
for tallness (T) or shortness (t), Tt will be segregated out during
meiosis as T or t.
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Differentiate between probability and independent assortment. In
independent assortment.
Chance and Probability
The probability of two or more independent events occurring together is
the product of the individual probabilities of such an event occurring
alone. This Product Rule is shown for two events in the equation 1/2 x
1/2 = 1/4. The principle may be visualized by use of a Punnett Square in
a test cross or known cross. According to Mendelian genetics, what is
the probability of having any one child be a boy or a girl? (1 in 2)
According to the Product Rule, what is the probability of a family
having five boys or five girls in a row? (½ x ½ x ½ x ½ x ½ = 1/32)
D. CHROMOSOMES AND GENES
*Molecular genetics study of the structure and function of
chromosomes and genes
*Chromosomes occur in pairsgenes occur in pairsalleles
(Tt)(TT)(tt)…T is an allele…t is an allelealternative
forms of a gene
FG 4
II. Genetic Crosses
A. GENOTYPE AND PHENOTYPE
1) Genotype the genetic makeup of an organism consists
of the alleles the organism inherits(PP) or (Pp) are 2
different genotypes…but both give a purple flower
2) Phenotype the appearance of an organism as a result of
its genotype
3) Homozygous both alleles are alike(TT) or (tt)
4) Heterozygous both alleles are different (Tt)
B. PREDICTING RESULTS OF MONOHYBRID CROSSES
*Monohybrid crossa cross between 2 individuals that
involves one pair of contrasting traits (TT) x (Tt)
*Punnett Square diagram to assist in predicting
The probability that certain traits will be inherited by
offspring
*Punnett Square diagram to assist in predicting
The probability that certain traits will be inherited by
Offspring
FG 5
*Genotypic ratio 1BB:2Bb:1bb
*Phenotypic ratio 3black:1brown
*Complete dominanceP totally dominates p…
*Incomplete dominance2 or more alleles influence
Phenotype…EX, FOUR O’CLOCKS (flower)
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*CodominanceBoth alleles are expressed in heterozygous
Offspring  no allele is dominate or recessive