Transcript Introduction to Genetics

Introduction to Genetics
Heredity
Also know as Biological inheritance.
 It is the key to differences between species.
 The branch of biology that studies heredity
is called Genetics.
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History of Heredity
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Gregor Mendel- Monk who worked with pea
plants to better understand heredity, sometimes
referred to as the father of modern genetics, came
up with Principle of Dominance.
The principle of dominance states that some
alleles are dominant and some are recessive.
The dominant allele is seen when in combination
with itself or a recessive allele.
The recessive allele is never seen when in
combination with the dominant, it is only seen
with in combination with itself.
This doesn’t apply to all genes.
Definitions of Mendel’s Work
Purebred- Produces offspring identical to
the parent.
 Trait- Easily observable characteristic
(shape, color, size, etc.)
 Hybrids- Organism produces by crossing
parents with differing characteristics.
 Gene- Factor that controls traits.
 Alleles- The different forms of a gene.
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Definitions of Segregation
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Phenotype- Physical characteristic of an
organism, the visible expression of an allele.
Genotype- Genetic makeup of an organism, the
actually allele combination.
Homozygous- An organism that has two identical
alleles for a particular trait.
Heterozygous- An organism that has two different
alleles for a particular trait.
Segregation
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We use a Punnett Square to visualize and predict
the outcome of crossings. Punnett squares are used
to predict the probability of a cross without
actually crossing organisms.
– Single Factor
– Double Factor
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Segregation- The separation of alleles during
gamete formation.
The Two-Factor Crosses on
Punnett Squares
If two genes are connected in some way
then the dominant alleles and recessive
alleles will be segregated as matched sets
into gametes.
 If genes are not connected then they should
segregate independently or undergo
Independent Assortment.
 Probability- The likelihood that a particular
event can occur.
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