Mendelian genetics Gregor Mendel Father of modern genetics

Mendelian genetics

Gregor Mendel • Father of modern genetics • Researched with pea plants •

Gregor Mendel • Father of modern genetics • Researched with pea plants • Developed ideas of dominance and trait segregation

Phenotype • Phenotype – Physical characteristics

Genotype • Phenotype – Physical characteristics • Genotype – Genes we inherit from our parents

Phenotype Notice the similarities: – Facial structure

Phenotype Notice the similarities: – Facial structure – Eyes

Phenotype Notice the similarities: – Facial structure – Eyes – Smile

Phenotype Notice the similarities: – – Facial structure Eyes Smile Ears

Phenotype Notice the similarities: – – – Facial structure Eyes Smile Ears Nose

Phenotype Notice the similarities: – – – Facial structure Eyes Smile Ears Nose Neck

Mendelian Genetics Mendel studied a number of characteristics in pea plants including: • Height - short or TALL

Mendelian Genetics Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW

Mendelian Genetics Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND

Mendelian Genetics Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY

Mendelian Genetics Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY • Pod shape - constricted or SMOOTH

Mendelian Genetics Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY • Pod shape - constricted or SMOOTH • Pod color - yellow or GREEN

Mendelian Genetics Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY • Pod shape - constricted or SMOOTH • Pod color - yellow or GREEN • Flower position - terminal or AXIAL

Mendelian Genetics We will work with the following three: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY • Pod shape - constricted or SMOOTH • Pod color - yellow or GREEN • Flower position - terminal or AXIAL

Predicting Inheritance To determine the chances of inheriting a given trait, scientists use Punnett squares and symbols to represent the genes. UPPERCASE letters are used to represent dominant genes. lowercase letters recessive genes. are used to represent

Predicting Inheritance For example: T = represents the gene for TALL in pea plants t = represents the gene for short in pea plants So: TT & Tt both result in a TALL plant, because T is dominant over t. t is recessive. tt will result in a short plant.

Predicting Inheritance For example: Mendels’ Principle of Dominance T = represents the gene for TALL in pea Some genes (alleles) are dominant and others are plants recessive. The phenotype (trait) of a dominant gene twill= be represents gene short gene. in pea seen when it the is paired withfor a recessive plants So: TT & Tt both result in a TALL plant, because T is dominant over t. t is recessive. tt will result in a short plant.

Predicting Inheritance Let’s cross a totally dominant tall plant (TT) with a short plant (tt). Each plant will give only one of its’ two genes to the offspring or F 1 generation. TT x tt T T t t

Predicting Inheritance Let’s cross a totally dominant tall plant (TT) with a short plant (tt). “Law” of Segregation Mendels’ Each plant will give only one of its’ two genes to Eachoffspring gene (allele) from the other so that the or separates F 1 generation. offspring get only one gene from each parent for a given trait. TT x tt T T t t

Punnett Squares Tt Tt The genes from one parent go here. The genes from the other parent go here. Tt Tt

Punnett Squares T T t Tt Tt

Punnett Squares T T t Tt Tt

Punnett Squares T T t Tt Tt

Punnett Squares T T t Tt Tt

Punnett Squares T T t Tt Tt

Punnett Squares t t T T Tt Tt F 1 generation

Interpreting the Results The genotype for all the offspring is Tt. The genotype ratio is: Tt - 4/4 The phenotype for all the offspring is tall. The phenotype ratio is: tall - 4/4

Punnett Squares T t ? ? Your Turn!! T ? ? t

Punnett Squares T t TT Tt Tt tt F 2 generation

Punnett Squares Next, give the genotype and phenotype T (F 2 generation). t ratios of the offspring T TT Tt tt

Punnett Squares Genotype ratio: TT - 1 T t T TT Tt tt

Punnett Squares Genotype ratio: TT - 1, Tt - 2 T t T TT Tt tt

Punnett Squares Genotype ratio: TT - 1, Tt - 2, tt - 1 T t T TT Tt tt

Punnett Squares Genotype ratio: TT - 1, Tt - 2, tt - 1 T t T TT Tt tt Phenotype ratio: Tall - 3

Punnett Squares Genotype ratio: TT - 1, Tt - 2, tt - 1 T t T TT Tt tt Phenotype ratio: Tall - 3, short - 1

Punnett Squares This is a monohybrid T cross. We worked with t only one trait. The height of the plant. T TT Tt tt

Punnett Squares This is a monohybrid T cross. We worked with t only one trait. The height of the plant. two T TT Tt Later we will work with a dihybrid cross, using the height of the plant and either seed color or seed shape. t Tt tt