Download Heredity

Objectives
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describe how genes influence the development of traits
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describe patterns of inheritance
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describe monohybrid and dihybrid crosses
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explain how heredity can be illustrated mathematically
Terminology
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Genetics
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Genotype
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Heredity
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Phenotype
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Hybridzation
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Heterozygous
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Monohybrid cross
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homozygous
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Dihybrid cross
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Gamete
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alelle
Mendel
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Known as the father of modern genetics
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Different forms of the same gene account for variations in
genetics
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An organism inherits two genes for a given trait, one from
each parent
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Some alleles are dominant over others
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The two genes of a given trait segregate during the
production of the gamete
Mendel
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Punnett Squares can be used to predict the outcome of a
cross.
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Write out the genotypes of the organisms
Designate letters to represent the traits you are tracing
Capital letters represent dominant traits
Lower case letters represent recessive trait.
Mendel
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Punnett Squares can be used to predict the outcome of a
cross.
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Complete dominance
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Monoybrid cross
Practice
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Purple flowers are dominant; white is recessive
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Purple flowered plant x white flowered plant
Practice
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When homogeneous tall pea plants (TT) are crossed with
homogeneous short pea plants (tt), ____ of the F1 plants and
____ of the F2 plants were tall.
Practice
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A heterozygous black-eyed male mouse is crossed with a
homozygous recessive red-eyed female mouse. Use a
Punnett square to predict the probability of the possible
offspring phenotypes. (Use B for the dominant allele and b
for the recessive allele.)
Practice
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In humans, the allele for free earlobes (F) is dominant over
the allele for attached earlobes (f). If one parent is
homozygous dominant for free earlobes and the other has
attached earlobes, can they produce any children with
attached earlobes?
Dihybrid cross
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Imagine that a given species has a gene for hair color (B =
dominant brown, b= recessive white) and a gene that
controls hair length (S= dominant short, s= recessive long).
Complete the dihybrid cross between parents with the
genotypes: BBSS and BbSs. Then list the genotypes and
phenotypes of the possible offspring that can be
produced.
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Incomplete dominance
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Neither trait is completely dominant
Heterozygous produces a blended trait
Ex red and white flowers; heterozygous=pink flowers
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Multiple alleles
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Codominance
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Polygenic traits
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Incomplete dominance
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Multiple alleles
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More than one allele code for a given trait
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Blood type IA, IB and I
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Codominance
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Polygenic traits
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Incomplete dominance
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Multiple alleles
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Codominance
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Both alleles are dominant
Results in both traits being present ( black and white feathers)
Polygenic traits
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Incomplete dominance
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Multiple alleles
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Codominance
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Polygenic traits
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Incomplete dominance
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Multiple alleles
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Codominance
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Polygenic traits
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Controlled by two or more genes.
Hair color and eye color
Sex Linked traits
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Carried on the sex chromosomes (X or Y)
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Colorblindness
hemophilia
Pedigree
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Traces the inheritance of a genetic trait through several
generations