Is Dominance Always Dominant?

Through the online lab activity I learned that dominance is not always dominant. Sometimes the dominant alleles were not expressed even though most of the time they were. I learned that this is because there are three different types of dominance, dominance, co-dominance, and incomplete dominance. Dominance is when a dominant trait is always dominant, for example the pea plants. Whenever two heterozygous plants were crossed, one being purple the other being white, the result was always 8 purple homozygous plants. This is a perfect example of dominance. Although sometimes when purple and white plants were crossed it didn't create all purple plants this was because they were homozygous, meaning that although the dominant allele was expressed, the recessive trait was also present.The second type of dominance, which is co-dominance, is when the two alleles are equally expressed. One example of this is human blood type. If one parent has blood type A and another has blood type B then the child will have the blood type AB making it co-dominant. Another example that I found in the virtual lab was that if you took a spotted seed plant and breeded it with a dotted seed plant you got a mix of both. These are both good examples of co-dominance as both alleles are equally expressed. The last type is incomplete dominance. This was expressed in the snapdragon flowers in the virtual lab. If the red plants were combined with white plants then you ended up with pink plants. Since neither of the alleles were dominant they mixed together to create a completely different allele. If the plant was homozygous or heterozygous seemed to have no affect on how the plant turned out meaning that this was an example of incomplete dominance. These three types of dominance showed me that dominance was not always dominant. 

Make the Right Call

Data Table 1:

Trial	Allele from Bag 1 (female)	Allele from Bag 2 (male)	Offspring’s alleles
1	B	b	Bb
2	B	b	Bb
3	B	b	Bb
4	B	b	Bb
5	B	b	Bb
6	B	b	Bb
7	B	b	Bb
8	B	b	Bb
9	B	b	Bb
10	B	b	Bb

Data Table 2:

Trial	Allele from Bag 1 (female)	Allele from Bag 2 (male)	Offspring’s alleles
1	B	B	BB
2	B	b	Bb
3	B	b	Bb
4	B	B	BB
5	B	b	Bb
6	B	B	BB
7	B	B	BB
8	B	b	Bb
9	B	B	BB
10	B	B	BB

Data Table 3:

Trial	Allele from Bag 1 (female)	Allele from Bag 2 (male)	Offspring’s alleles
1	B	B	BB
2	B	B	BB
3	B	B	BB
4	B	B	BB
5	b	b	bb
6	B	B	BB
7	B	b	Bb
8	B	B	BB
9	B	B	BB
10	b	b	bb

1.

	B	B
b	Bb	Bb
b	Bb	Bb

	B	B
B	BB	BB
b	Bb	Bb

	B	b
B	BB	Bb
b	Bb	bb

2. According to your results in Part 1, how many different kinds of offspring are possible when the homozygous parents(BB and bb) are crossed? Do the results you obtained using the marble model agree with the results shown by a Punnet square?

According to the result, If there are two homozygous parents, one that has the alleles BB and one with bb the child will always show the dominant trait. However if two children are hetrozygous then their offspring will have a 25% chance of showing the recessive allele. This means that there is only one possible offspring, which is an offspring with the alleles Bb. Both the Punnet square and the marbles had the same result which was a consistent 100% chance of the child showing the dominant trait.

3) According to your results in Part 2, what percentage of offspring are likely to be homozygous when a homozygous parent (BB) and a heterozygous parent (Bb) are crossed? What percentage of offspring are likely to be heterozygous? Does the model agree with the results shown by a Punnet square? 

According to our marble experiment there was a 60% chance of the offspring being homozygous and a 40% chance of the offspring being hetrozygous. I think that this result is a lot less accurate than the punnet square, which showed that 50% would be hetrozygous and 50% would be homozygous. I think that it is a lot less accurate because the marbles are chance where as the punnet square always has the same result and it never changes.

4) According to your results in Part 3, what diffrent kinds of offspring are possible when two heterozygous parents (BbxBb) are crossed? What percentage of each type of offspring are likely to be produced? Does the model agree with the results of a Punnett square? 

According to the results we obtained in part 3 when two heterozgous parents are crossed there are 3 possible outcomes, Bb, BB, and bb. That means that there is a 50/50 chance of being heterozygous or homozygous meaning there is a 50% chance for both. The marble experiment and the punnet square had very different results. In the marble experiment there was a 70% chance of having the alleles BB, a 20% chance of having the alleles bb, and a 10% chance of Bb. This is completely different from the punnet square which had a 25% chance of BB and bb, and a 50% chance of Bb.

5) For Part 3, if you did 100 trails instead of 10 trails, would your results be closer to the results shown in a punnett square? Explain. 
In my opinion there isn't really any way to know since it is all chance. I think that it might be closer to the results in the punnet square but you could do it a million times and it still might not get any closer. I think that its the same if two parents had 10 kids or a hundred kids. It is all chance, even the punnet square isn't completely accurate it just shows what the most probable chances are.

6) In a paragraph, explain how the marble model compares with a Punnett square. How are the two methods alike? How are they different? 
In my opinion the marble model and the punnet square are both very alike but also very different. The marble model is, in my opinion, a more accurate representation of the chances of a child having certain alleles. I think this because although the punnet square is scientifically accurate, the marble experiment represents reality better. The two methods are alike though because both are used to predict the probability of the alleles of a child. One bad thing about the marble method is that every time it will chage and there will never be a constant answere meaning that one time there could be a 90% chance of being hetrozygous and another there could be a 10%. In this way they are both alike and different.