z Dihybrid Crosses Turner College Career High School

z Dihybrid Crosses Turner College & Career High School 2017

Law of Independent Assortment § The inheritance patterns of one trait will not affect the inheritance patterns of another trait. § Independent assortment occurs during meiosis. § The alleles for a trait separate when gametes are formed. § These allele pairs are then randomly united at fertilization. § For a single human gamete, the possible combinations is an astounding … 223 or 8, 388, 608 combinations.

Review of Monohybrid Crosses § Remember, monohybrid crosses involve only ONE trait § Practice… § In fruit flies, red eyes are dominant to white eyes. § Cross a white-eyed fly with a homozygous dominant red-eyed fly. § Cross two heterozygous red-eyed flies. Draw a Punnett square for each cross, and determine the genotypic and phenotypic ratios.

Dihybrid Cross § Dihybrid Cross: a cross that shows the possible offspring for two traits. Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth § In this example, we will cross a heterozygous guinea pig with another heterozygous guinea pig. § Their phenotypes will be: black, rough x black, rough § Their genotypes will be: Bb. Rr x Bb. Rr

Dihybrid Cross § First, you must find ALL possible gametes that can be made from each parent. § Use the FOIL method … § Remember, each gamete must have one B and one R. Bb. Rr BR Br b. R br

Dihybrid Cross § Next, arrange all possible gametes for one parent along the top of your Punnett Square, and all possible gametes for the other parent down the side of your Punnett Square… Bb. Rr x Bb. Rr BR BR Br b. R br Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth

Dihybrid Cross § Then, find the Bb. Rr x Bb. Rr possible genotypes of the offspring. BR BR BBRR Br BBRr b. R Bb. RR br Bb. Rr Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth Br BBRr BBrr Bb. Rr Bbrr b. R Bb. Rr bb. RR bb. Rr br Bb. Rr Bbrr bb. Rr bbrr

Dihybrid Cross § How many of the Bb. Rr x Bb. Rr offspring would have a black, rough coat? BR § What is the genotype? § BBRR, Bb. Rr, BBRr, Bb. RR BR BBRR Br BBRr b. R Bb. RR br Bb. Rr Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth § 9 Br BBRr BBrr Bb. Rr Bbrr b. R Bb. Rr bb. RR bb. Rr br Bb. Rr Bbrr bb. Rr bbrr § How many of the offspring would have a black, smooth coat? § What is the genotype? § BBrr, Bbrr § 3

Dihybrid Cross § How many of the Bb. Rr x Bb. Rr offspring would have a white, rough coat? BR § What is the genotype? § bb. RR, bb. Rr BR BBRR Br BBRr b. R Bb. RR br Bb. Rr Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth § 3 Br BBRr BBrr Bb. Rr Bbrr b. R Bb. Rr bb. RR bb. Rr br Bb. Rr Bbrr bb. Rr bbrr § How many of the offspring would have a white, smooth coat? § What is the genotype? § bbrr § 1

Dihybrid Cross § Sooo… the phenotypic ratio is … 9: 3: 3: 1 Bb. Rr x Bb. Rr BR BR BBRR Br BBRr b. R Bb. RR br Bb. Rr Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth Br BBRr BBrr Bb. Rr Bbrr b. R Bb. Rr bb. RR bb. Rr br Bb. Rr Bbrr bb. Rr bbrr

More Practice… § In your notes, write this problem and solve… § In pea plants, yellow seeds (Y) are dominant over green seeds (y), and rounded peas (R) are dominant over wrinkled peas (r). § Cross a plant that is heterozygous for both traits with a plant that is homozygous recessive for both traits. § Draw a Punnett square to show all possible offspring, and determine the genotypic and phenotypic ratios. § First, determine the parents …

More Practice… § AND … the parents are … Yy. Rr x yyrr

More Practice… § Now create your dihybrid Punnett Square using Yy. Rr x yyrr. YR yr yr yyrr yr yr Yy. Rr Yr y. R yr

More Practice… § Now fill in YR the squares. § What is the genotypic ratio? 4: 4: 4: 4 Yy. Rr Yr y. R yr yr Yy. Rr Yyrr yy. Rr yyrr yyrr

z Endangered Species: The Sea. World Project

1 Black Rhino PE PPEe Pe PE Pe Pe PPEe PPee pe Pp. Ee Ppee

1 PPEe Normal Pp. Ee Normal PPee Normal Ppee Normal Black Rhino PE Lip/Normal Ears: 4/16 Pe PPEe PPee Lip/Long Ears: 4/16 Genotypic Ratio: 4: 4 Phenotypic Ratio: 8: 8 None will produce both traits. Pe Pe PPEe PPee Lip/Normal Ears: 4/16 Lip/Long Ears: 4/16 PPEe Pe PE Ppee pe Pp. Ee Ppee

2 Burmese Python Ss. Pp Sp s. P sp SP SSPp Ss. PP Ss. Pp Sp SSPp SSpp Ss. Pp Sspp SP Ss. Pp ss. PP ss. Pp sp Ss. Pp Sspp ss. Pp sspp

2 SSPP, SSPp, Ss. PP, Ss. Pp Normal Scales/Normal: 9/16 SSpp, Sspp Normal Scales/Albino: 3/16 ss. PP, ss. Pp Large Scales/Normal: 3/16 sspp Large Scales/Albino: 1/16 Phenotypic Ratio: 9: 3: 3: 1 3/16 will produce both traits. Burmese Python SP Ss. Pp Sp s. P sp SP SSPp Ss. PP Ss. Pp Sp SSPp SSpp Ss. Pp Sspp Ss. Pp s. P Ss. Pp ss. PP ss. Pp sp Ss. Pp Sspp ss. Pp sspp

3 Prehensile-tailed Porcupine TW Tt. Ww Tw t. W tw TW TTWw Tt. WW Tt. Ww Tw TTWw TTww Tt. Ww Ttww t. W Tt. Ww tt. WW tt. Ww tw Ttww tt. Ww ttww Tt. Ww

3 Prehensile-tailed Porcupine TTWW, TTWw, Tt. WW, Tt. Ww Normal/Normal: 9/16 TTww, Ttww Normal/Long: 3/16 tt. WW, tt. Tw Long/Normal: 3/16 ttww Long/Long: 1/16 Phenotypic Ratio: 9: 3: 3: 1 1/16 will produce both traits. TW Tt. Ww Tw t. W tw TW TTWw Tt. WW Tt. Ww Tw TTWw TTww Tt. Ww Ttww t. W Tt. Ww tt. WW tt. Ww tw Tt. Ww Ttww tt. Ww ttww Tt. Ww

4 Leaf-Nosed Bat Nt Nntt Nt nt nt nt Nntt Nntt nntt nntt nntt

4 Leaf-Nosed Bat Nt Nntt Nt nt nt Nntt Normal/Strong: 8/16 nntt Large/Strong: 8/16 nt Nntt nntt Phenotypic Ratio: 8: 8 nt Nntt nntt nt Nntt nntt 8/16 will produce both traits. nntt

5 Osprey Ps Ppss Ps ps ps p. S Pp. Ss pp. Ss ps Ppss ppss pp. Ss

5 Pp. Ss Normal/Normal: 4/16 Ppss Normal/Long: 4/16 pp. Ss Dark/Normal: 4/16 ppss Dark/Long: 4/16 Phenotypic Ratio: 4: 4 4/16 will produce both traits. Osprey Ps Ppss Ps ps ps p. S Pp. Ss pp. Ss ps Ppss ppss pp. Ss

6 Bongo Antelope HL Hh. Ll Hl h. L hl HL HHLl Hh. LL Hh. Ll Hl HHLl HHll Hh. Ll Hhll h. L Hh. Ll Hh. LL hh. Ll hl Hh. Ll Hhll hh. Ll hhll Hh. Ll

6 HHLL, HHLl, Hh. LL, Hh. Ll Normal/Normal: 9/16 HHll, Hhll Normal/Long: 3/16 hh. LL, hh. Ll Thick/Normal: 3/16 hhll Thick/Long: 1/16 Phenotypic Ratio: 9: 3: 3: 1 1/16 will produce both traits. Bongo Antelope HL Hh. Ll Hl h. L hl HL HHLl Hh. LL Hh. Ll Hl HHLl HHll Hh. Ll Hhll h. L Hh. Ll Hh. LL hh. Ll hl Hh. Ll Hhll hh. Ll hhll Hh. Ll