Bio 103, Lab 9, Mendel's Garden Revisited

Paul Grobstein's picture

One central piece of modern biology derived from Darwin's voyage to the Galapagos in the latter part of the 19th century. A second emerged, more or less independently, during the same period and resulted from the work of Gregor Mendel breeding pea plants and carefully observing the results. This work produced the first clear understanding of "laws of inheritance", and remains fundamental to most modern understanding of genetics.  And it revealed a mechanism for generation of diversity above and beyond mutation. 

In this lab you will be invited to participate yourself in making the kinds of observations and inferences that Mendel made. We will do so together studying not pea plants but fruit flies, and using not live animals (for which the studies would take weeks or months) but a computer simulation which is quite realistic in most important characteristics. The simulation, called FlyLab, is available to registered individuals (students in this class) at

After we've worked through some of the basic observations together, you should work in pairs to make observations yourself on some fly traits other than those we have explored together. Your task is to "make sense" of your observations starting with the basic ideas we develop together and adding whatever additional ideas seem necessary. Try and find some traits that yield unexpected results in a monohybrid cross, as well as some that yield unexpected results in a dihybrid cross. For the latter, be sure you have fully understood the behavior of each trait in monhybrid crosses first.

cejensen's picture

Fly Lab

After going over some basic concepts as a class, we started doing our own experiaments. I first looked at purple eyes (PR) and dumpy wings (DP) individually and together, and the results were similar to the experiments that we did as a class, so I chose other traits. I tried a female that had no wings (AP) and was tan (T), with a wild type male.

Female (AP;T) with Male (+) Offspring:

Female (+): 487

Male (T): 586

In the first cross, all the males were tan and all the females were wild type. Then, I crossed the offsring:

+: 413

AP: 128

T: 376

AP;T: 127

I wanted to explore this more with the gender, so I tried the same two traits on a male with a wild type female

Female (+) with Male (AP;T) Offspring:

+: 1066

All of the offspring in the first round were (+). Then I crossed the offspring:

Female (+): 378

Male (+): 200

Female (AP): 111

Male (AP): 71

Male (T): 184

Male (AP;T): 50

I needed to look at the traits individually to make sense of this. I started with T, because that one seemed to be linked to sex.

Female (T) with Male (+)

Female (+): 486

Male (T): 484

Again, all the males in the first round were tan, and all the females were wild type. I crossed the offspring:

Female (+): 256

Male (+): 282

Female (T): 234

Male (T): 241

Then, I tried the same thing with a tan male.

Female (+) with Male (T)

+: 1016 (all offspring wild type)

Then, I crossed the offspring:

Female (+): 503

Male (+): 278

Male (T): 251

All the females were wild type, while half of the males were tan and half were wild type. I believe that T is and X-linked trait. When just the mother is tan, she will pass the trait to her sons because the only X-chromosome they get is from her, while her daughters will be tan (if the trait is recessive), because they also get an X-chromosome from their father (if he is wild type). When the offspring are crossed, because the male is tan and the females have one X from their tan mother, this generation would be even. When just the father is tan, none of his children will be tan, because he will not pass the X-chromosome to his sons, and his daughters get another X-chromosome. However, when the offspring are crossed, because the daughters got an X-chromosome from their tan father, they would pass this on to half of their sons.


ED's picture

Small wings


To humor a predominant Western culture bias of how a human couple should look, and because of the statistic that men are physically bigger (at least taller/broader-shouldered) than women, I designed a female fly with small wings (M) and a male wild type (+). I hypothesized that this physical dynamic would be true in the fly world as well, because I could start with the assumption that the wild-type is the dominant trait.
I.         The first generation (H1) yielded results contrary to my hypothesis:
527 female +                      459 male M
(wild type)                          (mini-wings)
                     1.148 :    1
This surprised me due to my human bias and my assumption that + was dominant. Typically, when a wildtype fly is crossed with a fly that has a single non-wildtype trait, the H1 generation shows no phenotypical trace of the non-wildtype trait. In this case, not only did the non- wildtype trait show up—it showed up in the opposite gender of its parent who carried it (H1 males only had small wings, and H1 females only were +).
I changed my hypothesis to account for this when I remembered that the case with species other than humans sometimes ends up with the female larger than the male: female snakes are bigger than male snakes, and queen bees/ants are bigger than their male counterparts, for instance.
I continued to breed. At H4, there were males with +, but still more males with M and no females at all with M. By H6, the M had gone away completely, and stayed that way until I stopped breeding at H13.
II.      What was most interesting about this was how dominance played out between males and females. I did the experiment again but started the male with M (mini-wings) and the female as + to see if the trait really was true to gender, and didn’t just switch which gender got which trait in the parents.
In this case, females never carried the M trait, and males held onto it until H9 (as opposed to H6 in I.). At H9, there were only wildtype males and females.
My conclusion is that “small wings” is a trait only dominant in male flies, but then only present in male flies for a few generations (the number of + males was consistently only a little big higher than the number of M males) until it completely drops out.
I also tried a three-part experiment to see what would dominate between two seemingly handicapping traits: vestigial wings (VG) and incomplete wing veins (IR). A.) I mated a female with incomplete veins and a male with vestigial wings. I gathered data from that for 10 generations. B.) Then i mated a female with both RI and VG and a Male +, tested for 13 generations. C.) Then I flipped it and mated at female + and a male with RI and VG. I wanted to see what the differences would be/if there would be differences in which non-dominant/non-wildtype traits stuck to which gender depending on which initial parent had what.
A.  To be contin


sophie b.'s picture

fly lab





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Original parents:                                                                                                                                                                                female: wild type, male: sepia (SE)
I made a punnett square and expected that one quarter of the second round of offspring would have sepia eyes.
Phenotype             Number
Female: +            49
Male: +              48
 Phenotype                     Number     
Female: +                                35    
Male: +                                     44    
Female: SE                              17    
Male: SE                                   12      
My trial went as expected, the sepia eyes were clearly a recessive trait and gender didn’t seem to significantly impact the results.
I crossed four different types of traits in this trial, and I wasn’t quite sure what to expect. I thought that in the F1 maybe 1 quarter of the offspring would show recessive traits and in the F2, the offspring would be split into extremely small ratios.
Original parents:
Female: sepia, black bodied (SE, BL), male: bar eyed, cross veinless (B,CV)

            Phenotype                   Number     

Female: B                                  484       
Male: +                                    479        
 Total                                    963



          Phenotype                   Number       
Female: +                                  147         
Male: +                                    102         
Female: SE                                  48         
Male: SE                                    26         
Female: B                                  148         
Male: B                                     34         
Female: SE;B                                50         
Male: SE;B                                  13        
Male: CV                                    47    
Male: SE;CV                                 12         
Male: B;CV                                 104      
Male: SE;B;CV                               34         
Female: BL                                  41         
Male: BL                                    39         
Female: SE;BL                               16        
Male: SE;BL                                  7         
Female: B;BL                                46         
Male: B;BL                                  12         
Female: SE;B;BL                             17         
Male: SE;B;BL                                5         
Male: CV;BL                                 14    
Male: SE;CV;BL                               9    
Male: B;CV;BL                               31      
Male: SE;B;CV;BL                            11        
 Total                                   1013


This trial did not run as expected, as in the first round of offspring all of the females had barred eyes, and in the second there was an equal number of non barred eyes to barred for females, while males rarely had barred eyes. Additionally females never received the cross veinless trait, while many males did. In the F2 the ratios where somewhat what I expected, however I was shocked to see how dominant the bar eyed trait was in females.


ktan's picture

Mating flies

For my experiment, I wanted to see if the wild type is dominant in all the features, so I mated a wild type female to a male that that had different type of feature for each features (ex. Wild type female and yellow body male, wild type female and eyeless male, etc). What I found was that the wild type is dominant for all features EXCEPT Antennae, Eye Shape, and Wing Angle.

For the second part of my experiment, I mated a wild type female with a dichate angled male. The results showed that it was a 1:1 ratio of wild type and dichate angled. This told me that although the dichate wing angle is dominant over the wild type, a dichate wing angled fly has a heterozygous genotype (D+), since a homozygous genotype (DD) would result to all dichate wing angled offsprings.

Next, I mated two dichate wing angled flies, and it showed that the ratio of offspring was 1:2, wild type:dichate respectively. An explanation for the ratio being 1:2 instead of out of 4 is that one quarter of the offspring is DD, which may indicate lethal genes, and thus does not exist.

These results were similar when I mated two aristapedia (antennae) as well as two flies with different shaped eyes. This indicates that although these three features are dominant over the wild type, it does not mean that they are homozygous genotypes, but rather heterozygous. This phenomenon also tells us that there are such lethal genes that some offspring can inherit, which leads to death, such as sickle cell anemia in humans.

vdonely's picture


In this experiment we crossed the traits of flies to examine which traits pass on to offspring and which do not. I did about eight trials and in most of them the wild type was the dominant trait.
1)     1)  Wild type (+)     x      Singed Wings (SN).       P1=+    F1=+
2)     2)  Wild type (+)     x      Curly Wings (CY).           P1=+   F1=+
3)     3)  Wild type (+)     x      Bar Eye Shape (B).         P1=B    F1= B:+// 2:1
4)     4)  Wild type (+)     x      Crossveinless (CV).       P1=+    F1=+
5)     5)  Wild type (+)     x      Dichaete (D).                  P1=+    F1=+
6)     6) Wild type (+)     x      Miniature (M).               P1=+    F1=+
7)     7) Wild type (+)     x      Lobe (L).                          P1=L    F1=+
8)     8)  Lobe (L)              x      Purple (PR).                    P1=L    F1=+:PR:L:PRL//1:5:18:1
However, from this data I concluded that one trait that is more dominant than the wild type is the eye shape. As is evidenced with trials three, seven, and eight, the eye shape wins. In trials three and seven, when a wild type and eye shape were crossed, the offspring (P1) had dominant eye shape (either bar or lobe). When the offspring were crossed (F1) it consisted of a ratio of 2 to 1, bar shape to wild type.
Trial eight was interesting. I’m not sure if I did it wrong but when I crossed Lobe eye shape with Purple eye color, the eye shape was once again dominant. However, when the offspring crossed, there was a ratio of  1 to 5 to 18 to 1 or widltype to purple to lobe to purple lobe.  The highest number in this ratio was, of course, 18 which goes with the Lobe trait. Again, I find evidence that eye shape is the most dominant trait.
~Valerie Donely



paoli.roman's picture

This lab was extremely

This lab was extremely confusing. I understand that the purpose of the lab was to  comprehend how, why, and what traits  an organism receives from its parents. In this experiement we used an online lab program where we would design and combine different types of flies to then analyze what traits have been passed on from one generation to the other. I did my best to get a variety of results. What I seemed to get when I designed the female fly with curly wing shapes and purple eyes and the male with aristapedia antennas and star shaped eyes their offsprings (the majority of them basically 75 out of 103 were wild types (regular or normal types of flies). I tried the experiement 25 types and seemed to get the same results, that the dominat trait that seemed to be passed on from generation to generation did not really change and all offspings were wild types. In this case Mendel's 9:3:3:1 ratio, which is still somewhat confusing to me, I'm assuming really does not fit since none of the offsprings did not inherent one specific trait from neither the mother or father. Meaning that they were all consistent in their traits not showing any major diversity.

Karina G's picture

Lab 9

Kalyn Schofield

Karina Granadeno

Bio 103, Lab 9, Mendel's Garden Revisited
Fly Lab
Fly Traits:
Fly Experiment
Remember: Try and find some traits that yield unexpected results in a monohybrid cross, as well as some that yield unexpected results in a dihybrid cross.
TRUE BREEDING – No variation from initial parents to young with continued breeding.
F1 Generation (+) is all wild type trait. (3 to 1 ratio of wild VS Ebony/ degree of freedom)
F2 Ebony (E) type trait.
Original parents (P)
Variation with one element for both parents.
Each gene in two different states with parents giving one copy from each parent. Every individual has two versions of a gene.
Phenotype –Appearance
Genotype – Actual genes present
++ = Homozygous (SAME)
+E = Heterozygous (DIFFERENT)
1.)    Monohybrid Cross:
2.)    Dihybrid Cross:
Dihybrid Cross: ++, VGVG, EE, VGE
Experiment: 1
ORIGINAL PARENTS Female Fly: Wild Type (+)
ORIGINAL PARENTS Male Fly: Spineless Type (SS)
Female: + 494
Male: + 482
Female: +369
Female: SS 123
Male: +364
Male: SS 111
Chi-Squared Test Statistics: 0.9614
Degrees of Freedom: 3
Level of Significance: 0.8106
Ratio : 3:1
Experiment: 2
ORIGINAL PARENT: Female Fly: Wild Type (+)
ORIGINAL PARENT: Male Black: Wild Type(+); PR (PURPLE) Eyes; BL (Black Body)
Female: + 508
Male: +484
Female + 376; PR 12, BL 9; PRBL 97
Male + 360; PR 9; BL 8; PRBL 111
Conclusions: We have discovered that for the F1 generation using original parents that carry a wild type and a single variance such as spineless create the 3 to 1 ratio in their offspring. But when the original parent (single) has two variances such as eye color and wing type you receive the 2 to 2 ratio. Our problem with the third experiment was when both parents had two different variances it still generated the 2 to 2 ratio. This third experiment suggests that the trait variances are significant and will dictate the offspring ratio. So it’s not that Mendel’s trait formula of 3 to 1 and 9 to 3 are wrong it’s that it only applies to specific traits that are possibly dominant. You would need to test all flies in order to come to a definite conclusion.
We also ran other experiments and concluded that some crossings are not possible.
jmstuart's picture

During our experiments today,

During our experiments today, we looked at different crosses of fruit flies and how those crosses compare to the typical results expected in Mendelian genetics. We looked at several different traits: curly wings as opposed to regular wild wings and starry eyes instead of regular eyes. One interesting factor we had to account for was that the original specimens used in the parent generation for both of these traits by the fly lab were heterozygous instead of homozygous for the trait. This was slightly confusing, as it gave us a 3:1 ration for both the F1 and the F2 generation. We came to this conclusion by looking at possible punnett squares for these crosses.

Aside from traditional Mendelian genetics, traits can be influenced in real life by several different genes, or even be expressed in divergent ways, such as co-dominance or incomplete dominance. We're unsure of whether this could be mirrored in the fly lab, but when we tried to look at star eyes in conjuction with purple eyes (a true-breeding trait), our F2 generation produced ver non-mendelian results. Our ratios were not the expected 9:3:3:1, but we couldn't find an obvious exploration. In the future, we would possibly like to explore if this could have been an example of a sex-linked trait as opposed to a gene following the law of independant assortment.

 -stu and drich.

JPierre's picture

  Anna Chiles, Jennifer


Anna Chiles, Jennifer Pierre
Biology 103
Professor Grobstein
Lab 8 November 18, 2009
Hybrid and Dihybrid Crosses with Fruit Flies
                In today’s lab, we simulated the mating of fruit flies on FlyLab to examine the presence of certain traits. In facilitating the mating of two parental fruit flies of differing traits (i.e. a Wildtype female with an Aristopedic male), we were able to produce hybrid and dihybrid crosses to determine the genotypic and phenotypic make-ups of their first generation and second generation offspring. We were able to give credit to Mendel’s hypothesis that genes come in pairs and that there is a difference between genotypes and phenotypes. We found one example, however, that put into question Mendel’s theory and also the independence of traits. Below is a diagram of our findings from mating a Sable-colored female fruit fly with a Wildtype male.
                Female                                                                                                 Male
P             Sable (S)                                                              x                                              Wildtype (+)
F1          480 (+)                                                                 x                                              495 (+)
F2           236 (+)                                                                                                                  236 (+)
                268 (S)                                                                                                                 263 (S)
Noticing that this was different than our other results, we decided to run this cross again, this time using a Wildtype female and a Sable-colored male. Below are our findings.
                Female                                                                                                                 Male
P             Wildtype (+)                                       x                                                              Sable (S)
F1           500 (+)                                              x                                                                  497 (+)
F2           461 (+)                                                                                                                  258 (+)
                                                                                                                                                255 (S)
There is obviously a discrepancy between our findings and the findings of Mendel. We have concluded that this discrepancy must be related to gender/sex of the fruit fly. That we produced different results when we switched the traits from female to male suggests that body color, specifically Sable, is a sex-linked trait and, thus, does not apply to Mendel’s hypothesis. One explanation for this, borrowed from our lab discussion today, could be that genes are located in clusters on chromosomes and that they are not independent.


Terrible2s's picture

Dumpy wings

Today we looked at Mendelian Genetics and its application in regards to fruit flies. To begin with, we chose a trait that we wanted to explore.  This trait was "dumpiness" of the wings. When tested, we found that the "dumpy" trait was consistent with the ratio we learned in class: 3:1. Next, we looked at the color of the fruit flies and chose ebony as our example. We also found that, when tested, the ebony trait was consistent with the 3:1 ratio. After concluding that these two traits were true breeding, we decided to create a dihybrid cross between them. We then found that when these two traits were combined, they were consistent with the 9:3:3:1 ratio we also learned about in class. During our experiment, we tried a variety of traits (yellowness, eyeless, etc.) but ultimately reported these traits because we are always striving to be less wrong. Our results were as follows:

  Females Males
++ 284 278
DP, + 83 97
+, E 94 86
DP, E 33 28

-Lili and Terrible2s