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Introduction to Genetics
Ch. 11
Write the information on the slides
that show this symbol or that is this
color.
Genetics
• The scientific study of heredity
Gregor Mendel
• Father of modern
genetics
• Combined plant
breeding, statistics,
careful record
keeping
Mendel studied pea plants traits
(characteristics)
Genetic Information
• Gene – basic unit
of genetic
information
Allele – one form of a
gene
Principle of Dominance
• Some alleles are dominant and others
are recessive
Dominant vs. Recessive
•Dominant alleles
express a trait. (capital
letter)
•Recessive alleles are
only visible when paired
with another recessive
allele. (lower case letter)
Segregation
Separation of alleles during gamete formation
Gamete
Sex cells
Punnett Square
• Diagram used to predict and compare
variations resulting from a genetic cross
Homozygous vs. Heterozygous
• Homozygous - having
two dominant or two
recessive alleles.
(BB or bb)
•Heterozygous - having
both a dominant and
recessive allele. (Bb)
Genotypes
Phenotypes
• Genotype - genetic make up
• Phenotype – physical characteristics
Genotypes
Phenotypes (example)
genotypes
phenotypes
Hybrid
• Offspring of crosses between parents with
different traits
Principle of Independent
Assortment
• Genes for different traits can segregate
independently during the formation of
gametes.
• Example: genes for seed shape
segregate independently of those for seed
color
Incomplete Dominance
• One allele is not completely dominant
over another
Incomplete Dominance
• A flower has genes for white petals (w) and red
petals (r). When you mix white flowers with red
flowers you get pink flowers. How is this
possible? The w gene does not dominate over
the r gene and vice versa.
Both genes express themselves equally so you
get a pink color in the petals.
w
w
r
wr
wr
r
wr
wr
Codominance
• Both alleles contribute to the
phenotype
Polygenetic Traits
• Traits controlled by two or more
genes
Meiosis
• reproduction of gametes
(Similar to mitosis, but there are 2 divisions,
ending with ½ the number of
chromosomes of the parent cell.)
Diploid vs. Haploid
• Diploid – contains both sets of
homologous chromosomes
• Haploid – contains a single set of
chromosomes
Crossing-over is the process in which homologous
chromosomes exchange portions of their chromatids during
meiosis.
Gene Map
• Diagram showing the relative locations
of each known gene on a particular
chromosome