FALL, 2003

Mendel's Garden

Name:  Paul Grobstein
Subject:  Mendel's Garden
Date:  2003-11-11 12:38:39
Message Id:  7197
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.

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 monhybrid cross, as well as some that yield unexected results in a dihybrid cross.

Name:  Nancy Evans
Subject:  Fly Lab
Date:  2003-11-11 15:06:42
Message Id:  7200
For my first cross, I used a female with white eyes and a male with wild type (red) eyes.

First Generation:
50% white eyes
50% red eyes
*two flies appeared on the screen

Second Generation: (used two flies from first generation)
50% white eyes
50% red eyes
*four flies appeared on the screen

Third Generation: (used top two flies from second generation, both had red eyes)
75% red eyes
25% white eyes
*the white eyes only appeared in the males in this generation.

For my second cross, I used a female with spread wings (D) and a black body and a wild type male.

First Generation:
50% closed wings
50% open wings

Second generation:
75% wild type bodies
25% black bodies

Third Generation:
75 % wild type bodies
25% black bodies

HYPOTHESIS: Some traits do not follow the general ratio of 9:9:3:1. Some traits may not be able to be expressed at the same time (such as open wings and black bodies). Also, some traits may be muted in a sex (as in the case with females and white eyes).

Because I wrote my hypothesis after I performed the experiment, my hypothesis seems to follow the data. However, I don't know why this is true. Why could first and second generation females have white eyes but not third?

Name:  Sarah Kim and Natalya Krimgold
Username:  Anonymous
Subject:  Fly Lab
Date:  2003-11-11 15:12:49
Message Id:  7202
We discovered through several trials that not all of the traits were true-breeding. At first, we assumed that all traits were true-breeding, but we observed that half of the offspring of a curly-winged fly and a straight-winged fly were curly-winged and the other half were straight-winged. We realized that this outcome would not have been possible unless one of the traits (curly or straight wingedness) was heterozygous. We determined that the curly-winged trait was the heterozygous one because of previous tests with only straight-winged subjects. We tested breeding two curly-winged flies, and the results were 75% curly-winged and 25% straight-winged in the first generation. This leads us to believe that the curly-winged flies have one curly-winged gene and one straight-winged gene. The same was true of the aristapedia antennae trait.
Name:  Katie, Michelle
Subject:  Katie Ottati, Michelle Choi
Date:  2003-11-11 15:14:03
Message Id:  7203
We looked at dichaete wing angle and eyeless "eye shape" traits in the fruit flies.

- exhibits true breeding
- is not more dominant than "wild type" wing angle. Starting from the first generation of offspring, there was a 1:1 ratio of each wing angle.
- is not gendered. Both males and females exhibit the trait at the same frequency

- exhibits true breeding
- is recessive in relation to the "wild type" eye shape. In the first generation of offspring there were no phenotypically eyeless flies, in the second there was a 2:1 ratio of eyes to eyeless. In subsequent generations, whether or not there were eyeless flies depended on whether or not we selected a phenotypically eyeless parent.
- is not gendered.

Dicheate wing angle and eyelessness do not seem to have any impact on one another. When we bread an dicheate mother with wild type eyes and an eyeless father with wild type wings (and vice versa), each trait appeared with the frequency that would be expected based on the earlier experiments.

Username:  Anonymous
Subject:  Bessy Guevara, Vanessa Herrera, Shafiqah Berry
Date:  2003-11-11 15:18:27
Message Id:  7204
Hypothesis: After making the female with white eyes and the male wild typed, we hypothesized the the female would be recessive and the male dominant.

First Generation: Female (white eyes) Male (wild)

Second Generation: Female (wild) Male (white eyes)

Given that the white eyes appeared in the first process of mating, white eyes are clearly not a recessive trait in the male of the second generation, but is in the female of the first generation. We concluded that the white eyed trait is sex-linked since it turns up to be neither a dominant or recessive trait.

Third Generation: 1 Female (wild) 1 Male (wild)
2 Female (white) 2 Male (white)

Throughout the three generations the ration of wild to white is 1:1. In the last observation, only one of the males turned up with white eye. Yet we had to take in account that the female that turned up white in the Second generation still carried the white eyed trait from the first generation. We assumed the same for the males.

Subject:  Brianna Twofoot, Emily Breslin
Date:  2003-11-11 15:19:05
Message Id:  7205
We cross-bred a female fly with purple eyes and a male fly with minature wings. Here were the offspring they produced:

+ (wild type): 552
PR (like the mother): 204
M (like the father): 192
PR, M (combination of the mother and father traits): 64

These results yielded an approximate ratio of: 9:3:3:1
These were the expected results based on two parents with traits that we determined to be true breeding.

We discovered that the wing trait of Dicheate, where the wings are spread apart, was not true breeding. Any combination of breeding, over numerous generations, yielded a mysterious disappearance of the trait. This confused and baffled us. We determined that perhaps there is something inherent in the definition of "not true breeding" that allows traits to completely disappear or appear completely randomly.

Does a not true breeding trait mean that it is a mutation of a gene and cannot be inherited in the same statistical way that 'normal' genes are?

Subject:  Fly Lab
Date:  2003-11-11 15:20:02
Message Id:  7206
Manuela y LaToiya

We started with a female with "lobe" eyes, and a male with apterous wing size.(both flies were otherwise wildtype).
We bred them and got :

1002 flies -all lobe eyed w/ wildtype wings
we assumed that lobe eyes might be dominant, and that the female parent was homozygous(LL). To prove this, we checked to see if the lobe eyed trait was a true breed. and it was! :)
The male's apterous wings were also proven to be true breed.

Next we crossed the offspring of our lobe eyed female and apterous male. (lobe eyed wildtype) w/ the following results out of a total of 998 flies:
34 wildtype(ratio:1)
723 lobe eyed wildtype wings(ratio:21.265)
206 apterous wildtype eyes(ratio:6.059)
35 lobe eyed apterous(ratio:1.029)

For a second experiment we crossed a female with apterous wings and a male with lobe eyes.
For this experiment we got very similar results, which we could infer from that there are no sex linked traits.
Lobe eyes must have been dominant over wildtype eyes. And the apterous is a recessive gene. Both are homozygous.

We DO NOT have an explanation for why we hae such peculiar ratios.

Name:  su-lyn
Username:  spoon@hc
Subject:  Su-Lyn
Date:  2003-11-11 15:20:29
Message Id:  7207
I hypothesized that the wild type, being the most common phenotype, was the result of a dominant gene. I began by crossbreeding a female wild type (+) and male with curly wing shape (CY). Based on my hypothesis, I predicted that CY would be a recessive gene and that the crossbreeding would produce offspring (F1) that all had the + phenotype, and that their offspring (F2) would have the 3:1 ratio of + to CY.

Parents + and CY --> F1 50+ and 65CY i.e. 1 : 1.3 ratio
This fairly equal distribution suggests that + is not dominant over the CY. In fact, a greater proportion of offspring are CY phenotypes, but dominance is not total.

I crossbred a new pair of flies, CY and CY. Based on the assumption that they were homozygous, I predicted that they would produce offspring that were all CY in phenotype.

Parents CY and CY --> F1 32+ and 79CY i.e. 1 : 2.47 ratio
Subsequent crossbreeds of two CY offspring produced the following +:CY ratios
1 : 1.81
1 : 1.842
1 : 1.941
1 : 1.872

This implies that CY is not a homozygous phenotype. It is possible that one of the two variants that make up CY is recessive to +, and the other variant is dominant over +. This would help explain the first set of results in the crossbreed between + and CY.

Name:  Team Bitter
Subject:  Fly Lab
Date:  2003-11-11 15:26:43
Message Id:  7208
Team members: Paula "Calm" Arboleda, Romina "Cranky" Gomez

First Generation
Tan Female and Wild Male
519Tan male
504 Wild Female

Second Generation
WIld Female and Tan male
262 Tan male
271 Tan Female
257 Wild Male
266 Wild Female

Third Generation
Wild Female and Wild Male
514 Wild Female
243 Wild Male
249 Tan Male

Fourth Generation
Wild Female and Wild Male
508 Wild Female
521 Wild Male

When there is a tan female the tan gene appears in the male in the first offspring. We then crossed a wild female and a tan male and you had a 50% chance of getting a tan offspring in both the male and females. We then crossed a wild female and a wild male and we got the tan gene appeared only in the males but most of the offspring were wild type. When we crossed another wild female and another wild male, the tan gene disappears and you only get wild offspring. In other words, the tan gene disappears in the fourth generation. It is interesting to note that in the 3rd generation there were no tan females.

Name:  Charlotte and Elisabeth
Subject:  fly lab
Date:  2003-11-11 15:30:00
Message Id:  7209
Charlotte Haimes, Elisabeth Py

It seems that the variations present in the parent or parents increase the chances for the traits to take on the dominant gene in the offsprings.


Experiment 1:
Female (tan body) + Male (wild)
-> Female (228 wild) + Male (228 wild)
-> Female (255 tan) + Male (264 tan)
-> Female (473 tan) + Male (512 tan)
-> Female (477 tan) + Male (508 tan)
Tan body: dominant trait

Experiment 2:
Female (curly wings) + Male (purple eyes)
-> Female (257 W) + Male (218 W)
-> Female (271 C) + Male (240 C)
-> Female (175W) + Male (160 W)
-> Female (76 P) + Male (92 P)
-> Female (239 C) + Male (200 C)
-> Female (25 PC) + Male (32 PC)
-> Female (158 P) + Male (176 P)
-> Female (327 PC) + Male (328 PC)

Conclusion: Our hypothesis was proved right since in each experiment the offspring took on the variant traits. In the first experiment, the offspring showed to have tan bodies just like the female parent at the beginning of the chain. In the second experiment, the traits surface in further generations simultaneously in both sexes. Therefore, not only are the variant traits passed on to future generations, but also become more apparent as the chain progresses.

Name:  stefanie and alison
Subject:  sex-linked traits discovered?!
Date:  2003-11-12 14:53:44
Message Id:  7227
For our experimet, we decided to use bristle type as the observable characteristic. We crossed a wildtype female with a shaven male. In the F1 generation, both offspring had a wildtype phenotype. In the F2 generation, after crossing the offspring of the F1 generation, we found that the one to three ratio that had been visible in earlier experiments was present in this as well. There was roughly 1 shaven bristle type for every 3 wildtype bristle types.

For our next experiment, we mated a yellow-bodied female with a wildtype-bodied male. In the F1 generation half of the offspring were yellow and half wild-type, unlike the other experiments we performed, where all offspring were wild-type.

To ensure that it was not another type of variable we tested a yellow-bodied female with a yellow-bodied male, and offspring in three generations to follow were all yellow-bodied, this led us to conclude that yellow-bodiedness is in fact a pure-breeding trait.

Upon further review of our results, we realized that only the males were yellow-bodied, which would mean that the yellow body color gene is sex-linked.

Name:  Julia and Mariya
Subject:  fly incest
Date:  2003-11-12 14:57:29
Message Id:  7228
Our hypothesis is that if you breed two flies with different eye colors in a monohybrid cross, eventually you will see that one trait shows up more often than the other.
We first crossed a red-eyed male (wild type) with a red-eyed female (wild type.) We found that no matter how many filial generations you made, you kept gettng wild type flies. We repeated the experiment with purple-eyed flies, and found that all their kids and grandkids, etc, had purple eyes. Because these flies were true breeders, we know they are homozygous, having either pp (for purple eyes) or ++ (for wild type.)
Next, we bred a wild type fly with a purple-eyed fly. We expected that one of these traits would override the other in some cases, leading to generations with more of one eye color or the other. In the F1 generation, all the offspring had red eyes. In the F2 generation, though, about a quarter of the offspring had purple eyes.
p p
+ p+ (red) p+ (red)
+ p+ (red) p+ (red)

p +
p pp(purple) p+ (red)
+ p+ (red) p+ (red)

This supports the idea that the combination of two genes from two parents leads to four possibilities in each generation. In the F1 generation, because every offspring got one purple gene from the mother and one wild type gene from the father, they all had the same combination of one p and one +. In the next generation, though, offspring could inherit a p or a + gene from either parent. So one possibility was pp, one was ++, and the other two were +p. The phenotype of the +p genotype in the F2 generation would reveal which of these genes overrides the other. We found that 3/4 of the F2 generation had the wildtype phenotype, so we concluded that + was the gene that overrode p.

Username:  Anonymous
Subject:  Lindsay and Alice
Date:  2003-11-12 15:01:00
Message Id:  7229
We crossed a female with purple, regular shaped eyes with a male with purple, star-shaped eyes. We found their first generation of offspring to have half purple, regular shaped and half purple, star shaped. We then crossed the following F1 flies:

Purple, regular shaped + Purple, star shaped
Yielded half Purple, regular shaped and half purple, star shaped again.

Purple, regular shaped + purple, regular shaped
Yielded all purple, regular shaped

Purple, star shaped + purple, star shaped
Yielded 1/3 purple regular shaped and 2/3 purple star shaped.

When we isolated the eye shape gene and disregarded the eye color gene, the resuts of the cross
Star shaped + star shaped
still yielded this 2:1 ratio. So the fact that our results were the same when the two traits were isolated says that eye color and eye shape are not related in their inheritance. However, we do not know how to account for this 2:1 ratio when crossing eye shapes. We found this ratio odd because when we crossed flies with different eye colors, we came up with a 3:1 ratio in phenotype in the first generation, and either a 1:1 or 1:0 ratio in the second generation. We think that in order for this 2:1 ratio to occur there must be some other factor contributing to the flies' inheritance of eye shape.

Name:  lara kallich
Subject:  fly-love
Date:  2003-11-12 15:01:14
Message Id:  7230
1st cross: curly-winged female (CY) and wild-type male (+)
F(1): 50% CY, 50% +
- I was pretty surprised by these results, so for the next two generations I crossed a CY with a + from the previous generation:
F(2): 50% CY, 50% +
F(3): 50% CY, 50% +

Given that these results were a bit different from the all same/3:1 ratios that we saw in the earlier examples, I decided to test whether or not curly-wingedness was a true-breeding characteristic:

2nd cross: CY male and female
F(1): 50% CY, 50% +
F(2): 50% CY, 50% +
F(3): 50% CY, 50% +

Hypothesis: In a monohybrid cross, a trait that is characteristic of one of the parents that does NOT appear in F(1) is a true-breeding characteristic; conversely, a trait characteristic of one of the parents that DOES appear in F(1) is not a true-breeding characteristic.

Subject:  Fly Lab
Date:  2003-11-12 15:10:01
Message Id:  7231
Flicka Michaels

First I bred a tan female fly with a wildtype male fly.

F1- 1 female wildtype, 1 male tan
F2- 2 wildtypes, 2 tan (1 male and female of each)
bred male and female tan
F3- 2 tan (1 female tan, 1 male tan)

Next, I bred a female wildtype with a shaven male.

F1- 2 wildtypes
F2- 2 wild types, 2 shaven
bred 2 shaven
F3- 2 shaven

So, I can conclude from my results that tan coloring and shaven are true breeding traits since when I bred 2 tan flies or 2 shaven flies together the offspring continually showed these traits and no others.

Username:  Anonymous
Subject:  Flies
Date:  2003-11-12 15:12:05
Message Id:  7232
Jessica Knapp and Diana Medina

Hypothesis: There is equal chance for the offspring to have either father or mother traits.

Mother: Wild type (+) Father: Curly Wings (cy)

females + 271, Male + 247
females (cy) 271, Males (cy) 243

Second generation incest:
Mother (cy) father (+)

females: (+) 253 Males (+) 241
females:(cy) 238 Males (cy) 268

Our hypothesis seems to have proven correct as we came to see that in only changing one trait in the original parents, offspring were equally likely to have curly wings or wild type bodies.
As for the second generation we saw that characteristics equally carried through to the third generation.
There were variations but they were probably insignificant.

Name:  J'London and Enor
Subject:  FlyLab with Respect the the Characterisitcs of Shaven vs. Wild
Date:  2003-11-12 15:12:46
Message Id:  7233
We exerimented with the trair of hairtype within the fly community. We asser that The Wild Type hair trait are dominant when combined with the other types. However, when other hairtypes besidesWild Type are mated with the Shaven they tend to be dominant. The only offspring that showed shaven traits in physical form were when it was mated with another shaven type.

We very much enjoyed taking on the brain and logic of Mendel. We mated every "weird" thing with the wild type and they only produced about five offspring. Why were there no babies?

Username:  Anonymous
Date:  2003-11-12 15:12:53
Message Id:  7234
Maggie Tucker and Adina Halpern

We hypothesized that either dichaete-winged or wildtype would be a dominate gene, and whichever was not dominate would be recessive.

We bred a dichaete-winged fly with a wildtype fly. These flies produced an f1 generation of 50% dichaete-winged and 50% wildtype. This continued for all subsequent breedings involving one dichaete and one wildtype.

We did two types of breeding variation once this constant was found. For our first variation, we bred two dichaetes. We ended up with a ratio of 1 wildtype: 2 dichaete. This pattern remained constant when we continued to breed two dichaete from each subsequent generation.

For the second variation, we bred two wildtypes after the initial hybrid breeding. Our f2 generation consisted of all wildtyped. As two wildtypes were continuing to be bred, the dichaetes did not reappear.

Our results were not true to our hypothesis. Neither gene stood out as either recessive or dominate but we do not know why these results occurred.

Name:  Patricia Palermo
Subject:  Fly Eye Color Trends
Date:  2003-11-12 15:15:55
Message Id:  7235
We exained a purple-eye female / wild-eye male cross and analyzed their offspring following three breeding rules;

Key: W = wild eyed; P = Purple eyed

Rule #1: Breed W with P whenever possible (whenever both w and p exist among offspring).

Rule #2: Breed W whenever possible.

Rule #3: Breed P whenever possible.

Test #1: Applying Rule #1
P 1:1
F1 2:0
F2 1:1
F3 2:0
F4 1:1
F5 1:1
and follows with breeding as 1:1

Test #2: Applying Rule #2

P 1:1
F1 2:0
F2 1:1
F3 1:1
F4 2:0
F5 2:0
and follows with breeding as 2:0

Test #3: Applying Rule #3

P 1:1
F1 2:0
F2 1:1
F3 0:2
F4 0:2
F5 0:2
and follows with breeding as 0:2

The interesting occurance was that consistancy with seeing just wild type in test two (which was what we were looking for) arrived by trial F4. But the consistancy of seeing just purple in test 3 (which was what we were after in that test) arrived earlier, in the F3 breeding. This lead us to infer that the red contains something thats holds on to a "hiddenpurple " longer. While the purple does not hang on to a red trait for any length of time.

Name:  Maria S-W and Rochelle Merilen
Date:  2003-11-12 15:16:18
Message Id:  7236
We found the process of attempting to breed fruit flies virtually more frustrating and irritating than it could be in reality. We attempted two monohybrid crosses, once with antennae and once with body color and both times the result was not the phenotypical ratios that mendel's model has. During our first attempt, in which we bred a wild type male with a AR antennae female, the offspring was half and half. So we tried a different trait: Body color. The first generation did have the same apperance, but subsequent generations always resulted in a 50-50 split between the Wild type body color and the black body color. We are not sure why this happened. We think it might be bad luck. Or perhaps the computer software. We also considered that perhaps the specific traits that we chose resulted in our unusual results.
Username:  Anonymous
Subject:  fly-love: a revision
Date:  2003-11-12 15:47:16
Message Id:  7237
I would like to retract some of the data I posted earlier. It is still the case that curly-wingedness is not a true-breeding trait; however, when a CY male and female are crossbred the ratios in F(1) and following generations of CY to + was NOT in fact 50%:50% or 1:1 - it was in fact closer to 2:1. The error was solely due to carelessness on my part; I apologize for any confusion and hope that this statement clears things up.
Username:  Anonymous
Date:  2003-11-12 15:47:51
Message Id:  7238
above remarks by Lara Kallich (

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