mendelian genetics - all saints middle school science · mendel’s principles of genetics...

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