Counting Corn

In the 1600’s, people had no video games, so instead they had various activities such as husking bees, where if you get a red ear of corn, something good happens to you. But why only red years of corn? Mainly because there were not that much. Because red was the recessive gene. But since nobody knew that because Mendel was born in 1822 so he didn’t exist yet to publish his genetics theory. Now forward this 400 years to where we are now, and instead of having yellow dominant ears, we are counting purple dominant yellow recessive ears of corn for biology class(for points and our grade, not for kisses). We want to see the ears of corn and determine if the ears of corn are a good fit for Mendel’s theory or not. So we first counted the phenotypes of the kernels on five rows of a Monohybrid Cross, which should be a 3:1 ration for purple to yellow and the kernels should be all smooth.. Down below I have our diagram and picture:

Next we took a Test cross. Our expected was equal number for all types. Here is our diagram and picture:

Then we put our data into a chi square:

It has a 20-50% chance of the difference caused by chance, so therefore, it’s a good fit. So then our hypothesis of it being a 1:1:1:1 ratio is a good hypothesis and should not be tossed away. A good fit means how well the model(the corn) fits a set of observations. A poor fit is when you have to reconsider if there is a faulty approach and the hypothesis might be incorrect. A data might have poor chi square fit when Genes are linked or on the same chromosome, dramatically increasing the chance of a phenotype appearing. Another is when there is faulty data or just plain really really bad luck.

Now we have a problem set to finish.

1. Problem: A large ear of corn has a total of 433 grains, including 271 Purple & starchy, 73 Purple & sweet, 63 Yellow & starchy, and 26 Yellow & sweet.

Your Tentative Hypothesis: This ear of corn was produced by a dihybrid cross

(PpSs x PpSs) involving two pairs of heterozygous genes resulting in a theoretical (expected) ratio of 9:3:3:1.

Objective: Test your hypothesis using chi square and probability values.

The total number of kernels is 840. So the expected would be:

Purple and Smooth 9/16 * 433 = 243.6

Purple and Wrinkled 3/16 * 433 = 81.2

Yellow and Smooth 3/16 * 433 = 81.2

Yellow and Wrinkled 1/16 * 433 = 27.1

so after calculating that out would be:

3.08 + .82 + 4.07 + .04 = 8.01. According to the chi square, this is a bad fit.

2. Problem: In a certain reptile, eyes can be either black or yellow. Two black eyed lizards are crossed, and the result is 72 black eyed lizards, and 28 yellow-eyed lizards.

Your Tentative Hypothesis: The black eyed parents were Bb x Bb.

Objective: Test your hypothesis using chi square analysis. In this set, because only two values (traits) are examined, the degrees of freedom (df) is 1. SHOW ALL WORK!

If we draw a Punnet Square Bb and Bb, we should get a ratio of 3:1.

The total is 100, so we use that to calculate:

Black eyes should be 75 but is 72

Yellow eyes should be 25 but is 28

Calculating that out I get of chi value of .12+.36=.48 which is a good fit.

3. Problem: A sample of mice (all from the same parents) shows

58 Black hair, black eyes 16 Black hair, red eyes

19 White hair, black eyes 7 White hair, red eyes

Your tentative hypothesis: (what are the parents?)

Since the result is about 9:3:3:1, this is probably a dihybrid cross, making its parents HhEe and HhEe. The total offspring is 100, so the expected is:

9/16 of 100 = 56.25

3/16 of 100 = 18.75

3/16 of 100 = 18.76

1/16 of 100 = 6.25

I calculated this out to get:

.05 + .40 + .003 + .09 = .54

On the chi square, this is a good fit.

Meiosis

    Why meiosis? Asking that question is like asking, “who am I?” Meiosis creates our identity. Many say it’s to pass on our genes. However, that is not always the case as just recreating the same genes would let us be infected by invading species faster. The function of meiosis is to both pass on our genes and give genetic diversity. Genetic diversity is a very powerful tool. WIthout it, a single invasive species can desecrate the whole population. Just like how Jedi and Sith in Star Wars are a lot more powerful than the simple clones and droids, which number by the millions and can be destroyed by a single one of the former, genetic diversity in humans lead to higher survivability, at the cost of less offspring.

    In this lab, we will be making a stop motion video of meiosis and I will be doing some research on meiosis and answer the questions.

    In meiosis, “crossing over” and “independent assortment” promote genetic variation. In crossing over, chromosomes swap their DNA in order for cells to inherit different traits from different parents. This occurs in prophase 1. In anaphase I and II, independent assortment causes different chromatids to get pulled to different sides of the cell randomly. This process is entirely random so there are 4 ways to assort in anaphase 1, and 4 ways in anaphase 2, making it 4*4 = 16 ways to independently assort the chromatids.

    Non-disjunction is when a problem occurs in meiosis and the chromosomes do not separate, causing one of the cells to have twice the amount and one of the cells to have none.This can occur in meiosis 1 and also in meiosis 2. Non-disjunction occurs because of a failure of a checkpoint. To be exact, the spindle checkpoint. This checkpoint monitors the correct formation of the spindle fibers, so if this checkpoint fails to work correctly, the spindle fibers do not work on one end, making the chromosomes get pulled all to the other side. A failure in cohesin(the glue tying the two chromatids together) would also cause non-disjunction, such as if it did not un-stick, one of the spindle fibers have to break, causing the non-disjunction.

    Pandas have 42 chromosomes. They are considered to have the same ancestor as bears, but normal bears have 74 chromosomes. Why is that? This is because the panda’s chromosome is very similar to two linked chromosomes of a bear. From this, we can deduce that the deviation in the species is because of non-disjunction, when the chromosomes do not split apart during meiosis. This can explain why the panda’s chromosome has two linked chromosomes and why the panda and the bear share a common ancestor. The panda is just a mutation(I apologize to all the pandas in the world).

    This lesson could be improved by showing two sides with egg cell and sperm cell production, and then showing the two cells combining with fertilization. And the zygote that appears afterward.

    Here is the link: https://m.youtube.com/watch?v=ipxyacE5Bso