Punnett Squares 4/7/2015. A specific region of DNA that codes for a particular protein

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1 A secific region of DNA that codes for a articular rotein Punnett Squares Alleles are different versions of the same gene - Ex. Purle flowers and white flowers Dominant Alleles - use a caital letter to reresent them Recessive Alleles - use a lower case letter to reresent them Examle: Brown is dominant = B Blue is recessive = b ***Dominant trait is exressed unless both alleles are recessive*** Genotye - genetic makeu for a secific set of genes - reresented by 2 letters: BB, Bb, bb Phenotye - hysical characteristics or traits - what it looks like: Brown or blue eyes Examle: Bb (genotye) carries one allele for brown and one for blue eyes, however they will have brown eyes (henotye) Homozygous: urebred - Two of the same alleles for one trait - Will have two of same letters: BB or bb Heterozygous: hybrid - Two different alleles for one trait - Will have two different letters: Bb BB Bb bb Brown eyes Brown eyes Blue eyes 1

2 A) BB B) Bb A)Bb B) Brown hair C) bb A) BB B) Bb C) bb A)BB B) Bb C) bb The likelihood that an event will occur Probability = # of one kind of ossible outcome = % total # of all ossible outcomes When the word or is used you add the odds 1/6 + 1/6 = 2/6 When the word and is used you multily the odds 1/6 x 1/6 = 1/36 What is the robability of rolling a 6 on a die? - 1/6 What is the robability of rolling a 6 ora 5 on a dice cube? - 1/6 + 1/6 = 2/6 What is the robability of rolling a 6 anda 5? - 1/6 x 1/6 = 1/36 2

3 Predicts all ossible genotyes resulting from a cross Mendel s Generations: P = arents F1 = offsring (1 st generation) F2 = offsring of F1 (2 nd generation) 1. Identify the dominant and recessive traits 2. Identify the henotye of each arent 3. Identify the genotye of each arent 4. Fill in the Punnett Square 5. Write the henotye ratio 6. Write the genotye ratio Ste 1: identify the dominant and recessive traits Purle is dominant (P) White is recessive () Ste 3: identify the genotye of each arent P X Ste 2: identify the henotye of each arent Purle flower X white flower Ste 4: fill in Punnett Square P P P Ste 3: identify the genotye of each arent P X P P P - Organisms inherit 2 coies of each gene, one from each arent - During gamete formation genes searate and only one version makes it into the gamete (egg or serm) Ste 5: Write the genotye ratio 50% P 50% Ste 6: Write the henotye ratio 50% urle 50% white 3

4 Law of Indeendent Assortment - allele airs searate indeendently of each other during meiosis (gamete formation) - More likely to be searated: * if on different chromosomes * the further aart on a chromosome Law of Dominance - Traits have two alleles (one from the female and one from the male) - Some alleles are dominant (A) and some are recessive (a) Dihybrid Crosses Mendel s Exeriments Conducted exeriments that examined the inheritance of 2 different traits: Ex: flower color and ea shae Wondered if traits would be assed on together or searately Using urebred lants, he conducted many exeriments using a variety of trait combinations Ex: flower color and ea shae ea shae and od color Mendel s Results The F1 generation of crossing 2 urebred lants would result in heterozygous lants: The lants all exressed the dominant gene but carried the gene for the recessive trait (how did he know that?) Cross 2 urebred lants When Mendel crossed the F1 generation which was heterozygous for both traits, he discovered that the F2 generation exressed all combinations of the 2 traits 4

5 Mendel s Conclusion Law of Indeendent Assortment - Allele airs, one from mom and one from dad, searate indeendently of each other during meiosis. Dihybrid Crosses are used to show how alleles indeendently sort Process (stes) are just like monohybrid crosses (single trait) with one extra ste Process for doing dihybrid roblems Ste 1: Identify dominant and recessive traits Ste 2: Identify the henotyes of each arent Ste 3: Identify the genotyes of each arent Ste 4: Determine ossible allele combinations using FOIL method Ste 5: Comlete Punnett Square Ste 6: Write out henotyes and ratios Ste 7: Write out genotyes and ratios Ste 4: Use F.O.I.L. to identify all ossible allele combinations: RY, Ry, ry, ry RrYy Use combinations to fill in Punnett Square: RY, Ry, ry, ry 5