Mendelian Genetics
• Who was Gregor Mendel?
– Considered the “father of genetics”
– Developed the principles of genetics that still apply today
Mendelian Genetics
• How did Mendel describe the P generation / parental generation?
– Mendel’s P generation organisms were true breeding
– true breeding organisms have identical genes for a particular trait
– true breeding organisms can be represented with TT or tt
Mendelian Genetics
• How did Mendel describe the F1 generation / first filial generation?
– Mendel’s F1 generation organisms were hybrids
– hybrid organisms have two different genes for a particular trait
– hybrid organisms can be represented with Tt
Mendelian Genetics
• How did Mendel describe the F2 generation / second filial generation?
– Mendel’s F2 generation contained both true breeding organisms and hybrid organisms
Mendel’s Principles of Genetics
• Identify Mendel’s hypotheses associated with genetics.
– there are alternate forms of genes that determine heritable characteristics
– for each inherited characteristic, an individual has two genes, one from each parent
Mendel’s Principles of Genetics
– sperm and egg carry only one gene for a characteristic
– if an individual has two different genes for a characteristic, the gene that is expressed is considered dominant, and the gene that is not expressed is considered recessive
Mendel’s Principles of Genetics
• Define Mendel’s principle of segregation
– pairs of genes separate during meiosis
– fertilization of an egg cell by a sperm cell pairs genes again
Mendel’s Principles of Genetics
• Define Mendel’s principle of independent assortment.
– each pair of genes separates independently during meiosis
Mendel’s Principles of Genetics
• Define the following terms associated with Mendelian genetics.
• dominant gene: a gene that is expressed in a heterozygous individual (Aa)
• recessive gene: a gene that is not expressed in a heterozygous individual (Aa)
• homozygous (dominant): describes an individual with two genes that are both dominant for a characteristic (AA)
Mendel’s Principles of Genetics
• Define the following terms associated with Mendeliangenetics.
• homozygous (recessive): describes an individual with two genes that are both recessive for a characteristic (aa)
• heterozygous: describes an individual with two different genes for a characteristic (Aa)
• genotype: refers to the genes found within an organism• phenotype: refers to the physical appearance genes
code for
Monohybrid Crosses
• What is a monohybrid cross?
– a genetic cross involving one characteristic
Monohybrid Crosses
• What is a Punnett square?
– a chart used to organize the details of a genetic cross
Punnett Square Practice
Punnett Square Practice
Punnett Square Practice
Punnett Square Practice
Dihybrid Crosses
• What is a dihybrid cross?
– a genetic cross involving two characteristics
Dihybrid Cross Worksheet
Hierarchy of Dominance
• What is complete dominance?
– refers to a characteristic for which one gene is dominant and one gene is recessive
Hierarchy of Dominance
• What is incomplete dominance?
– refers to a characteristic for which two genes are blended together when expressed
– the offspring show an intermediate phonotype, between the two parents
Incomplete Dominance
Incomplete Dominance
Hierarchy of Dominance
• What is codominance?
– refers to a characteristic in which two genes are expressed at the same time
– two phenotypes are expressed in the offspring
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