Gummy Bear Lab

*This lab was done in collaboration with Amanda Diana & Ananya Bhattacharya

1.) 30 Pink: 10 White

Hypothesis: Since pink appears to be the dominant trait, having a pink:white, 3:1 ratio, the parents of these offspring must both be carriers for the recessive white.

Analysis:

As previously stated, this group of offspring has a 3:1 ratio, exhibiting simple Mendelian dominance. In order to get this ratio, the crossed parents must be two heterozygous pink gummy bears (Pw x Pw).

The result of crossing these two parents is three pink gummy offspring (one homozygous and two heterozygous) and one homozygous white gummy offspring, or a 3:1 ratio. Thus proving that this litter of gummy bears follows simple Mendelian dominance.

2.) 15 Pink: 30 Pink-White: 16 White

Hypothesis: Here we have an interesting batch of offspring. ¼ of the offspring are pink, ¼ are white, and ½ are pink and white. This appears to be a 1:2:1 (pink: pink-white: white) ratio. The parents of these offspring most likely are carrying a gene for white and pink, and these genes can both be expressed simultaneously.

Analysis: Because approximately half of the offspring are showing both traits, it can be assumed that pigment trait is co-dominant. This means that heterozygous genotypes will code to show both yellow and white, as opposed to complete dominance, where in heterozygous genotypes the more dominant gene surfaces.The parents for these offspring are infact carrying a gene for white and pink, as is shown below.

This also supports the hypothesis because the ratio of possible offspring here are also 1:2:1.

3.) 20 Pink: 18 White: 14 Green: 19 Pink-Green

Hypothesis:

This particular set of offspring is interesting in that four different phenotypes are exhibited. Since the offspring exhibits four different possible pigmentations it is likely to believe that the mode of inheritance may be multiple alleles, similar to the mode of inheritance for blood types.

Analysis:

Due to the evidence shown in this punnett square, we can conclude that the mode of inheritance is multiple allele. All possible phenotypes are demonstrated in the genotypes of the potential offspring shown in the punnett square. There is also a 1:1:1:1 ratio demonstrated in the Punnett Square equivalent ratio for the phenotypes of the offspring, supporting the idea that the dominance for this set of gummy bear genes is multiple alleles.

4.) 38 White

Hypothesis: In this grouping, all 38 gummy bears were white. Since all of the offspring share a phenotype, we can conclude that the parents must be homozygous white. The entire litter would not be all white, since white has proven to be a recessive trait in every other litter thus far, unless both parents had a genotype of ww.

Analysis: The offspring have a ratio of 1, meaning all offspring are white. These offspring are displaying simple dominance. To yield theses results, the parents of this litter of bears must have been homozygous white (ww x ww).

By crossing these two bears we see that all the offspring will share a genotype and phenotype. (ww, white).

5.) 15 White: 15 Pink: 30 Orange

Hypothesis: In this grouping, there are 15 white / yellow gummy bears, 15  pink gummy bears, and 30 orange gummy bears. The ratio of the offspring is 1:2:1 (Red:Orange:White). From these results we can assume that both parents have a genotype of heterozygous orange. We know this because heterozygous parents will always display a 1:2:1 ratio when expressing incomplete dominance.

Analysis: The offspring have a ratio of 1:2:1, meaning the amount of orange offspring is double the amount of white and pink offspring. This litter is displaying incomplete dominance, in which the parents are heterozygous orange gummy bears (as displayed in the punnet square below, with PW = orange).

In this graph, we are comparing the phenotype frequency for each gummy bear phenotype.