BEANS AND GENES/GENETIC PROBABILITY

JOYCE CRAFT                    HYDE PARK ACADEMY    
                               6220 S. STONY ISLAND AVE.
                               CHICAGO, IL 60637
                               1-312-947-7180

OBJECTIVES:  
     1.  DISTINGUISH EXPECTED AND OBSERVED GENETIC RATIOS.  
     2.  DEMONSTRATE THAT IN GENETIC CROSSES, AS THE NUMBER OF OFFSPRING 
INCREASES, THE DIFFERENCE BETWEEN OBSERVED AND EXPECTED RESULTS DECREASES.  
     3.  DEMONSTRATE THE PRACTICAL APPLICATIONS OF GENETIC PROBABILITIES.  

MATERIALS:  
     EACH TEAM NEEDS 2 BOXES*; 100 RED BEANS; 100 WHITE BEANS; 
     CALCULATOR (OPTIONAL).                   
     NOTE- RED AND WHITE BEANS SHOULD BE THE SAME SIZE & AND SHAPE.

STRATEGIES:  
     EACH BOX REPRESENTS A PARENT ORGANISM.  EACH BEAN REPRESENTS A  GENE.  EACH 
BOX WILL CONTAIN 100 BEANS. IN EACH CROSS, A RED BEAN REPRESENTS A DOMINANT GENE 
(R=RED) AND A WHITE BEAN REPRE-    SENTS A RECESSIVE GENE (r=WHITE).  THE CONTENT 
OF EACH BOX IS DETERMINED BY THE GENETIC MAKEUP OF EACH PARENT. THE CLASS IS    
SEPARATED INTO LAB TEAMS OF 2 OR 3 STUDENTS EACH.  2 MEMBERS OF THE TEAM WILL EACH 
HAVE A BOX OF 100 BEANS.  THE THIRD PERSON RECORDS THE DATA. 

    THE TEACHER BEGINS THE ACTIVITY BY PLACING THE GENOTYPES OF THE PARENTS (P1) 
ON THE BOARD.  EACH TEAM NOW COUNTS OUT THE APPROPRIATE NUMBERS AND COLORS OF 
BEANS PER BOX:  RR=100 RED BEANS; Rr=50 RED AND 50 WHITE BEANS; rr=100 WHITE 
BEANS. 
                                
    THE TEACHER NOW TIMES THE CLASS FOR ONE MINUTE DURING WHICH EACH STUDENT PAIR 
PULLS 2 BEANS AT A TIME (ONE FROM EACH BOX)           AND ARRANGES THE PAIRS IN 
ROWS: RR;Rr;rr.  AT THE END OF THE MINUTE, COUNT THE NUMBER OF RR,Rr AND rr. USING 
THIS DATA, CALCULATE THE OBSERVED RATIO** FOR EACH GROUP.  

    NEXT THE TEACHER RECORDS THE RAW DATA FROM EACH TEAM INTO A CHART ON THE BOARD 
AND ADDS RESULTS TO GET CLASS TOTALS OF RR,  Rr AND rr.  CALCULATE CLASS RATIOS. 

    WORK THE CROSS ON PAPER AND CALCULATE THE EXPECTED RATIOS. COMPARE  EXPECTED 
RATIOS WITH OBSERVED TEAM RATIOS AND OBSERVED CLASS RATIOS. WHICH ARE CLOSER TO 
THE EXPECTED AND WHY? 

    VARIATIONS:
    EACH TEAM CREATES A CROSS, DETERMINES EXPECTED RATIOS ON PAPER, CREATES PARENT 
GENOTYPES WITH BEAN BOXES, DOES 4 TRIALS OF ONE MINUTE EACH, CALCULATES  OBSERVED  
RATIOS AND DISCUSSES  DIFFERENCES BETWEEN SINGLE AND MULTIPLE TRIAL RESULTS. 
                             
    JELLY BEANS,OR OTHER OBJECTS MAY BE SUBSTITUTED FOR BEANS. SOLICIT STUDENTS 
FOR IDEAS! 

    *OATMEAL BOXES; QUART SHERBERT CONTAINERS; ETC. **CALCULATION OF RATIOS:  
TOTAL RR=A, Rr=B, rr=C.  A+B+C=D D/4=E. A/E=1ST RATIO; B/E=2ND RATIO; C/E=3RD 
RATIO.  EXPRESS RATIOS IN WHOLE NUMBERS.