Gregor Mendel “Father of modern genetics” Researched with pea plants Developed ideas about inheritance and how parents pass the traits to their offspring.

Alleles Mendel discovered that there are at least 2 different versions of each gene. Today, we call those alleles. Alleles can be dominant or recessive. Dominant = allele that always shows its trait Recessive = allele that shows its trait only if there are 2 copies

Alleles Alleles are represented by two-letter combinations. Example: RR, Tt, pp Dominant = capital letter (RR, Ww, Bb) Recessive = lowercase letter (Rr, ww, mm) The letter is often the first letter of the dominant trait. (Ex. Round peas = Rr) Dominant allele is always written first. Dd, not dD

Genotype vs. Phenotype Genotype –Genes we inherit from our parents –BB, Bb, bb Phenotype –Physical characteristics –hair color, blood type

Phenotype –Facial structure –Eyes –Smile –Ears –Nose Notice the similarities: Not all phenotypes are visible, BUT they are all determined by your genotype.

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

Dominant vs. Recessive Two of the same alleles (RR or rr) If they are both dominant, then they are homozygous dominant (RR). What do you think it is called if they are both recessive? One dominant and one recessive allele (Rr) Homozygous Heterozygous homozygous recessive

Predicting Inheritance To determine the probability of inheriting a given trait, scientists use 4-square boxes called... Punnett Squares Rr RRRRr r rr

Punnett Squares Rr RRRRr r rr Allows us to predict the possible genotypes and phenotypes of the offspring Show us the probability of getting a certain genotype or phenotype

Punnett Squares TtTtTt The alleles from one parent go here. The alleles from the other parent go here.

Punnett Squares Parents: TT x tt TT tTtTtTt t

Punnett Squares TT tTtTtTt tTtTt

Punnett Squares TT tTtTtTtTt tTtTtTtTt

TT tTt tTtTtTtTt

Punnett Squares TT tTt t

Punnett Squares TT tTt t Possible Genotypes of the Offspring

Interpreting the Results TT tTt t The genotype for all the offspring is The probability of offspring genotype being Tt = The phenotype for all the offspring is The probability of offspring phenotype being tall = Tt 100% tall 100%

Round or Wrinkled Seed Parents: Rr x Rr Rr RRRRr r rr Genotype Probabilities:Phenotype Probabilities: RR: 25% rr: 25% Rr: 50% Round: 75% Wrinkled: 25%

Gray or White fur Parents: Gg x gg Gg gGggg gGggg Genotype Probabilities:Phenotype Probabilities: Gg: 50% gg: 50%Gray: 50% White: 50%

Red (dom) or Black Eyes Parents: Homozygous dom & homozygous rec RR rRr r Genotype Probabilities:Phenotype Probabilities: Rr: 100%Red: 100%

Pink (dom) or white flowers Parents: Homozygous dom & heterozygous PP PPP pPp Genotype Probabilities:Phenotype Probabilities: PP: 50% Pp: 50%Pink: 100%