What in the World is Wolbachia?

For our very last AP Biology lab EVER, my class looked into a very interesting type of bacteria: Wolbachia. Wolbachia is a genus of intracellular bacteria that lives inside the bodies of arthropods and nematodes. Wolbachia bacteria must live and reproduce inside the of insect host cells, as they are endosymbiotic. What exactly does Wolbachia do? Well that is both simple and complicated – Wolbachia bacteria alters the sex of their hosts, usually from male to female.

When I first heard what Wolbachia did, I genuinely could not believe it. How could a bacteria alter gender?? After doing some research, I discovered a few different ways:

1. In some species, infection of Wolbachia bacteria can cause females to reproduce parthenogenetically, meaning that eggs can develop without male fertilization. This would mean that the resulting offsprings would be genetically identical to the mother; they would all be female as well. Wolbachia causes the cells to stop mitosis at anaphase, when the two sets of chromosomes are suppose to separate, which leads to diploid nucleuses. This does not allow the duplicated chromosomes to separate, and thus results in a diploid female.

2. In some species, Wolbachia infections causes fertilized eggs to always develop as female by suppressing the production of masculinizing hormones. This makes it so genetically male embryos develop as females.

3. In some species, Wolbachia causes male embryos to abort in early development. This does not directly change a particular insect’s gender, but it does contribute to the overall feminization effect of Wolbachia.

As you can probably infer, Wolbachia bacteria reside in the reproductive systems of arthropods. Something even more interesting about Wolbachia is that it can be transmitting two ways: horizontally through contact with another organism or the environment , or more commonly, through the female’s eggs. Males cannot pass the bacteria to their offspring due to the absence of eggs in males. As mentioned previously, Wolbachia is a parasite in arthropods. Parasitism is when one organism benefits at the expense of the other – in this instance, the Wolbachia lives and reproduces inside of the reproductive organs of insects and some other arthropods, but causes an effect to the body. Interestingly enough, Wolbachia isn’t always considered a parasite: Inside filarial nematode hosts, Wolbachia is mutualistic – both organisms benefit.

Some of our Lab Equipment 

For this lab, we all went home and captured insects to use for samples and data. The purpose of this lab was to determine if any of these insects have Wolbachia DNA. This lab was like a master lab, involving many types of biotechnology that we have experimented with over the year. We began by crushing the insects’ thoraxes (where their reproductive organs lie) in a lysis solution. We then added DNA primer and a “master solution”, which contained free nucleotides. We ran these samples in a thermocycler to conduct PCR. The process of PCR (polymerase chain reaction) is used to amplify two regions of the DNA so that we could later successfully isolate the Wolbachia data. After the PCR, we began gel electrophoresis to see the results of these amplified products. The presence or absence of the genes on the gel served as date for us to determine whether or not the insects were infected with the Wolbachia parasite. The results of the gel electrophoresis are shown below.

I (Marissa) worked with Davis and Elina, and out of all of the groups, ours seemed to be the most successful in getting accurate data. From our results we can conclude that my insect (found in San Francisco by the other biology teacher) did not contain Wolbachia DNA while Davis’ did. As you can see, only one other person seemed to find Wolbachia DNA, and many other groups were not able to successfully extract insect DNA at all.

Me holding my Data Sample!

I very much enjoyed this lab. I will admit, there were a lot of steps, and some of it was extremely confusing. However, I could definitely tell that this was a very good lab to review all of the technology and lab experiments we had done all year. We used micropipettes, gel electrophoresis, and various machines to conduct PCR. In a perfect world, there would have been more data from the rest of our class so that we could tell the frequency of Wolbachia in our area. I think Wolbachia is an incredibly interesting genus of bacteria, and I am glad that we got to learn about it at all. I was very proud of myself for participating with the micropipettes on this last lab – usually I am too shaky to do it, but this time I was able to relax and compose myself in order to do it. What a great lab to end the year with!

Making Meiosis Move

I collaborated with Abi Grassler to create a moving project that demonstrates the steps of meiosis in gamete cells. We used craft supplies – mainly Pipe Cleaners – to symbolize various organelles and depict the changes made and steps taken during meiosis. We then took pictures on an IPad, and used the Stop Motion application to string these pictures together in a motion film. You can view this video below:

Meiosis is a form of sexual reproduction and cell division. Unlike mitosis, which creates clones of the parent cell, meiosis creates genetic diversity – especially through crossing over, which occurs during Prophase I. Meiosis is similar to mitosis in that the cell goes through similar phases in both processes. However, meiosis goes through two divisions, producing four daughter cells, as opposed to mitosis which divides only once and produces two.

While Abi and I enjoyed using Stop Motion and taking pictures to create an animation of meiosis, using the craft supplies was challenging. Both Abi and I were originally unclear about the general process of meiosis, and we found that this confusion (on top of the struggle of using Pipe Cleaners and the time crunch) resulted in a lot of difficulties. However we did our best, and we are both really happy with the outcome of our project!

Work Cited:

Reece, Jane B., Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, and Robert B. Jackson. Campbell Biology. AP Edition ed. Vol. 10. Boston, MA: Pearson Learning Solutions, 2014. Print.

The Miracle of Mitosis – Cell Division

Title: Examining Cells from the Tip of an Onion Root to Determine the Time the Average Cell Spends in Each Phase of Mitosis

Purpose: The purpose of this lab is to determine how long cells spend in each phase of mitosis

Introduction: Mitosis is the process in which a cell divides, splitting the nucleus, and creating two identical daughter cells. Mitosis can be broken down into five major phases: Prophase, Prometaphase, Metaphase, Anaphase, and Telophase. The cell spends most of cell life in Interphase, however, which is a time for cell growth and DNA replication. Interphase takes part during the G2 cycle. During Interphase, a nuclear envelope encloses the nucleus, which contains one or more nucleoli/nucleolus. The cetrosomes have duplicated, and chromosomes cannot be seen yet. The chromosomes begin to become apparent during Prophase, the first phase of cell division, where the chromatin fibers condense and tightly coil. The nucleoli disappear during this phase and the mitotic spindle begins to form. Though prometaphase is the next phase, where the nuclear envelope begins to disintegrate and the kinetochores attach to the centromere, for the sake of this lab we did not identify this phase because it is so short and hard to distinguish. Next, during metaphase, the nuclear envelope completely dissolves and the centrosomes are now at opposite polls of the cells. The chromosomes line up in the middle at the metaphase plate, and the sister chromatids are attached to the kinetochore microtubules coming from opposite poles. Anaphase comes next, which is when the spindle fibers begin to shorten and the two sister chromatids of each pair start to part, moving toward opposite ends of the cells. The cell begins to elongate, and by the end of anaphase the two ends of the cell have equivalent and complete collections of chromosomes. The last phase is telophase,  which is when two daughter nuclei form in the cell and the envelopes begin to reform. The nucleolus split, and the cleavage furrow begins to form. After telophase is cytokinesis, which is not technically a phase because cytokinesis is the splitting of the cell, and mitosis refers to the division of the nucleus. Each stage of mitosis takes different amount of time, and while the observation of a complete cell cycle (24 hours) under a microscope is impossible, scientists can get a idea of the time spent in each stage by studying an onion root cell, and counting how many cells within the onion root are in each stage, thus creating an average percentage of cells per phase.

Method:

1. Take a sample of an onion root tip and put it under an electric microscope to observe.

2. Count and record how many cells there are total in the section of the cell you are looking at.

3. Identify which phase each cell is in, and record the data.

4. Once you have a count of how many cells are in each phase, divide the cells in each phase over the total amount of cells to find the average percent of cells in each phase. Then, by multiplying that percentage by the number of minutes in an hour (1440 minutes), find the amount of time the cells spend in each phase.

5. Record all date. Compare the percent of cells in each stage to find approximately how much time each phase would take by looking at the percentages relative to each other.

Data:

Here is a picture of the Onion root tip that I took through the microscope

Possible Errors:

Because we are fortunate enough to live in a age of advanced technology, I was able to use my phone to take a picture through the microscope. This thus magnified my view of the onion root tip, lowering the cell count. While this made the cells easier to observe/manage, but minimizing the amount of cells I now realize I also minimized my data accuracy. Therefore, the percent of cells in each stage, as well as the time a cell spends in each phase, is more of an average. The more data one has the higher chances of accuracy, and because I only had two points of data that also takes away from the accuracy of the results.

Works Cited:

“Online Onion Root Tips.” Online Onion Root Tips. The Biology Project, n.d. Web. 02 Nov. 2014. <http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.html&gt;.