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Fundamentals of Genetics (Ch.9.1 + 9.2)
Genetics is the field of biology devoted to
understanding how characteristics
are transmitted from parents to offspring.
Objectives
1. Explain the significance of Mendel's
experiments and observations, and the laws
derived from them.
1.1 Explain the concept of independent events.
1.2 Understand that the probability of an
independent event is not altered by the
outcomes of previous events.
1.3 Describe Mendel's experiments and
observations.
1.4 Describe the relationship between genotype
and phenotype.
1.5 Use the concept of the gene to explain
Mendel's laws.
1.6 Describe the ideas of dominant and recessive
traits with examples.
1.7 Consider the value of the punnett square by
creating examples of mono and dihybrid
crosses.
1.8 Explain the law of segregation.
THINK, PAIR UP, AND SHARE!
Think, Pair, Share
2.10 Discuss the
similarities and differences
between sex chromosomes
and somatic
chromosomes.
2.11 Using examples from
living organisms
discuss the importance of
asexual and sexual
reproduction to their growth
and survival.
Independent Events
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If events happen independently of each other
they...
If events were to be dependent on each other
they...
Mendel the Monk
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Gregor Mendel was an Austrian Monk, who
specialized in statistics.
Heredity – transmission of characteristics from
parents to offspring.
Traits – a category in which alternate
characteristics can be observed
Mendel's Crosses and Results
Mendel's Laws

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Law of Segregation – a pair of factors is
segregated or separated during the formation of
gametes.
Law of Independent Assortment – factors for
different characteristics are distributed to gametes
independently.
WHAT DO THESE MEAN EXACTLY?
Genes and Alleles
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Gene is a segment of DNA on a chromosome that
controls a particular hereditary trait.
Alleles are the different types of characteristics the
gene can express.
These alleles are represented by letters.
G = capital means dominant
g = lower case means recessive
Genotype vs Phenotype
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Genotype – its “genetic type” or make-up
Phenotype – its visible appearance – what we see
Dominant – will reflect appearance regardless of
the other trait's characteristics.
Recessive – only will reflect appearance if paired
with another recessive.
Punnett Squares – Monohybrid and
Dihybrid Crosses P Generation –
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1
Parental
F1 Generation – Fillial
(offspring)
Pure – breed only a
specific trait
Strain – plants that are
pure for a specific trait
Y = Dominant Yellow Genotypes: 2 Yy, 2 yy
y = Recessive Green
Phenotypes:
2
yellow, 2 green
Dihybrid Cross
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R - round
r – wrinkled
Y – yellow
y - green
Homozygous vs Heterozygous

Homozygous – allele is
with the exact same
allele as itself.

Heterozygous – allele
is paired with a
different allele
(characteristic).
GG
Gg
Dominance

Complete Dominance
one allele “pwns” the
other. You only see the
one phenotype.
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Incomplete
Dominance two or more alleles
influence the
phenotype.
Codominance
both alleles are
expressed
independently. Blonde
(B) + brown (B') hair.
Assignments + Practice

Test Cross – if you
know something
expresses a certain
phenotype, but want to
know its genetype for a
trait, cross is with a
purebreed and observe
the results!
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9.1
9.2
Punnett Square
Problems
Objectives
Achieved?
1. Explain the significance of Mendel's
experiments and observations, and the laws
derived from them.
1.1 Explain the concept of independent events.
1.2 Understand that the probability of an
independent event is not altered by the
outcomes of previous events.
1.3 Describe Mendel's experiments and
observations.
1.4 Describe the relationship between genotype
and phenotype.
1.5 Use the concept of the gene to explain
Mendel's laws.
1.6 Describe the ideas of dominant and recessive
traits with examples.
1.7 Consider the value of the punnett square by
creating examples of mono and dihybrid
crosses.
1.8 Explain the law of segregation.