Heredity • Genetic problems – Apply rules of probability • Multiplication rule • Key terms 1. Genethe genetic material on a chromosome that contains the instructions for creating a particular trait (codes for a trait) 2. Allele one of several varieties of a gene 3. Locus location on a chromosome where a gene is located
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Heredity Genetic problems –Apply rules of probability Multiplication rule Key terms 1. Gene the genetic material on a chromosome that contains the instructions.
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Heredity
• Genetic problems– Apply rules of probability
• Multiplication rule
• Key terms1. Gene the genetic material on a chromosome
that contains the instructions for creating a particular trait (codes for a trait)
2. Allele one of several varieties of a gene3. Locus location on a chromosome where a
gene is located
Heredity
• Key terms4. Homologous pair every cell contains two
copies of each chromosome, one inherited from each parent.
• Test cross• A test cross is a mating of an individual whose
genotype you are trying to determine with an individual whose genotype is known.
• You will always know the genotype of the individual that expresses the recessive trait.
Heredity
• Dihybrid Crosses– Genes for two different traits are observed at the same
time.
• Incomplete Dominance– The alleles for a gene do not exhibit the dominant and
recessive behaviors.– Instead, the combined expression of two different
alleles in the heterozygous condition produces a blending of the individual expressions of the two alleles.
Heredity
• Codominance– Both inherited alleles are completely expressed
• Multiple alleles• Epistasis
– Occurs when one gene affects the phenotypic expression of a second gene.
– Ex. mice hair color• One gene codes for the presence or absence of pigmentation• Second gene codes for the color of pigmentation (black or brown)• Phenotypic expressions: CCBB, CCBb, CcBB, CcBb
CCbb, Ccbb ccBB, ccBb
Heredity
• Polygenic inheritance– The interaction of many genes to shape a single
phenotype.– Example: human height
• Linked genes– Genes that reside on the same chromosome and
cannot segregate independently.– Genes that are linked are usually inherited
together.
Heredity
• Sex-Linked Inheritance– Sex chromosomes– Sex-linked or X-linked– Examples
• Hemophilia– Inability to code for all factors required to form normal blood
clots.
• Color-blindness– Inability to distinguish red from green
• Duschenne’s Muscular Dystrophy (MD)– Absence of an essential muscle protein called dystrofin.– Results in deteriorating muscles and loss of coordination.
Heredity
• X-inactivation– During embryonic development in female
mammals, one of the two X chromosomes in each cell does not uncoil into chromatin.