Gregor Mendel

Mendel was an Austrian monk. Mendel formulated two fundamental laws of heredity in the early 1860's. He had studied science and mathematics (including statistics) at the University of Vienna. Mendel’s knowledge of statistics later proved valuable in his research on Heredity – the transmission of characteristics from Parent to Offspring. Mendel's work was unrecognized until 1900.

Mendel’s Conclusions In his crosses each trait had a Dominant Factor which masked, or dominated the other factor for a specific trait. the other trait we call the Recessive Factor. In a true-breeding cross (BBxbb) the recessive factor is masked in F1 but appears in F2

Mendel’s Conclusions Law of Segregation: Each organism contains two factors for each trait; factors segregate in the formation of gametes. When two gametes combine during fertilization, the offspring have two factors controlling a specific trait. Law of Independent Assortment: states that factors for different characteristics are distributed to gametes independently.

Genetics Vocabulary Gene - the unit of heredity; a section of DNA sequence encoding a single protein Alleles - two genes that occupy the same position on homologous chromosomes and cover the same trait Locus - a fixed location on a strand of DNA where a gene or one of its alleles is located

Genetics Vocabulary Homozygous - having identical genes (one from each parent) for a particular characteristic. Heterozygous - having two different genes for a particular characteristic.

Genetics Vocabulary Phenotype - appearance Genotype - genetic makeup

Genetics Vocabulary Dominant - the trait that appears in the heterozygous condition. Recessive - the trait that is masked in the heterozygous condition.

Genetics Vocabulary Monohybrid cross - cross involving a single pair of genes, one trait P – “parents” F1 – “kids” F2 – “grandkids”

Genetics Vocabulary Punnett squares - used to aid in predicting the probability that certain traits will be inherited by offspring Probability - is the likelihood that a specific event will occur or is the likely outcome a given event will occur from random chance

How To: Monohybrid Crosses On the Back of Your Notes StepsNotesExamples

Monohybrid Crosses (only one trait) Ineeda Know Ph.D. is trying to identify the potential genotypes of offspring of a white male rabbit and a heterozygous black female rabbit.

Ineeda Know Ph.D. is trying to identify the potential genotypes of offspring of a White male rabbit and a heterozygous black female rabbit. Black is dominant to white in bunnies. StepNotesExample 1. Determine the dominant and Recessive trait Will be stated in the problem Black is dominant to white in bunnies

Ineeda Know Ph.D. is trying to identify the potential genotypes of offspring of a White male rabbit and a heterozygous black female rabbit. Black is dominant to white in bunnies. StepNotesExample 2. Assign letters for the trait Dominant trait gets the capital letter Recessive traits gets the lower case letter B = black b = white

Ineeda Know Ph.D. is trying to identify the potential genotypes of offspring of a White male rabbit and a heterozygous black female rabbit. Black is dominant to white in bunnies. StepNotesExample 3. Determine genotype for parents Each parent has two alleles White male = bb Heterozygous black female = Bb

Ineeda Know Ph.D. is trying to identify the potential genotypes of offspring of a White male rabbit and a heterozygous black female rabbit. Black is dominant to white in bunnies. StepNotesExample 4. Put parents on the square Separate parental alleles Bb x bb B b b

Ineeda Know Ph.D. is trying to identify the potential genotypes of offspring of a White male rabbit and a heterozygous black female rabbit. Black is dominant to white in bunnies. StepNotesExample 5. Determine genotype of offspring Punnett square holds offspring genotypes Genotype = letter code Bb x bb B b b Bbbb Bbbb

Ineeda Know Ph.D. is trying to identify the potential genotypes of offspring of a White male rabbit and a heterozygous black female rabbit. Black is dominant to white in bunnies. StepNotesExample 6. Determine genotype ratio Count offspring in the Punnett square There are two correct ways to represent your data genotype ratio = 2 Bb: 2 bb 2/4 Bb, 2/4 bb

Ineeda Know Ph.D. is trying to identify the potential genotypes of offspring of a White male rabbit and a heterozygous black female rabbit. Black is dominant to white in bunnies. StepNotesExample 7. Determine phenotype ratio Phenotype = what they look like *ratio MUST add up to the number of boxes* Count offspring in the Punnett square phenotype ratio 2 black:2 white

Practice Problems A pure-breed white flower crosses with a pure-breed purple flower. Purple is dominant to white. Determine the genotypes of the flowers. Show the punnett square What is the genotype of the F1 generation What is the phenotype of the F1 generation

Genotype = Pp Phenotype = Purple

More Practice A homozygous black guinea pig is crossed with a heterozygous black guinea pig. B = blackb = brown Determine the genotypes of the parental guinea pigs. Show the punnett square. What are the genotypes? What are the genotype ratio? What are the phenotypes? What are the phenotype ratios?

Genotypes = BB and Bb Genotype Ratio = 2BB:2Bb Phenotypes = All Black

Even More Practice If you had a black guinea pig how could you tell it’s genotype was homozygous and heterozygous?

Use a test cross: cross with a pure breed recessive and look at the F1 generation