Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
I. Introduction A. Genes are not always dominant or recessive in their relationship. II. Incomplete dominance A. Also called blending inheritance. B. The heterozygous is a blend of the two alleles. Red x White = Pink Black x White = Grey Examples A. Incomplete dominance – Four o’clock flowers 1. Genes: a. b. 2. R = Red R’ = white Genotypes/Phenotypes a. b. c. RR = Red RR’ = Pink R’R’ = white B. Cross two pink four o’clocks RR’ Pink R F1 cross RR’ Pink R’ G =RR : RR’ : R’R’ 1 : 2 : 1 R RR R’ RR’ R’R’ P =Red : Pink : White 1 : 2 : 1 RR’ III. Co-dominance A. Both of the contrasting alleles are expressed. B. Red x White = red with white patches. EXAMPLES A. Co-dominance – Shorthorn cattle 1. Genes: a. R = red b. W = white 2. Genotypes/Phenotypes a. RR = red b. RW = red & white c. WW = white B. Can you get a red & white calf by crossing two red cows? NO RR x RR = RR C. Cross a red & white bull with a white. F2 cross RW Red&white WW White R W W RW WW W RW WW G= RW:WW 2 : 2 P = Red : White &White 2 : 2 IV. Traceback • TRACEBACK- When you know some of the “families” genotypes/phenotypes, you can determine the other family member’s genetics using a traceback. • Step 1: Read the information given. • Step 2: List each family member on its given level (i.e. grandparents at top, parents on next level, children on next, etc) • Step 3: Write in the given knowledge (genotypes/phenotypes). • Step 4: Use deductive reasoning to figure out the rest of the family members genotypes/phenotypes. EXAMPLE: • Sarah has a BROWN male German Shepard and a tan female German Shepard that recently had 6 puppies. BROWN (B) is dominant to tan (b). Four of the puppies where BROWN (B) and the other two were tan (b). The female’s mother and father were both PUREBRED tan (b). The male’s mother was BROWN and the father was tan. What are all of the genotypes of the family? Male’s Mother Male’s Father Father BB or Bb Father Bb Female’s Mother Female’s bb bb X Mother bb Brown puppies Bb Tan puppies bb bb V. Test Cross 1. test cross- used to determine if an individual exhibiting a DOMINANT TRAIT is homozygous or heterozygous for that trait. 2. Test crosses involve breeding the individual in question with another individual that expresses a RECESSIVE version of the same trait. 3. If all offspring display the dominant phenotype, the individual in question is homozygous dominant; if the offspring display both dominant and recessive phenotypes, then the individual is heterozygous. EXAMPLE: In chinchillas, brown fur (b) is recessive to BLACK fur (B). A farmer wants to produce purebred BLACK chinchillas. He purchases a BLACK chinchilla from a pet store. How can he determine if the chinchilla he purchased is purebred? ANSWER! MEMORIZE WORDING!! 1. The farmer breed his black chinchilla with a brown chinchilla. 2. If ALL of the offspring are BLACK, the chinchilla is most likely HOMOZYGOUS, PUREBRED. 3. If ANYof the offspring are brown, the chinchilla is HETEROZYGOUS, HYBRID. Let’s work the problems on the back using the overhead projector.