Old Dominion University/BIOL294-Genetics/Rinehart-Kim/Module 7/Lac Operon Regulation

Draw and describe the regulation of the Escherichia coli lac operon in the following situations:

1. In the absence of lactose (disregard presence or absence of glucose).

When there is no lactose (inducer) the repressor protein is bound to the operator, and the induction of lactose metabolism genes is repressed.

• In the presence of lactose (disregard presence or absence of glucose).

When Lactose is present, the inducer binds to the repressor protein which changes its shape. This makes it so the repressor can no longer bind to the operator gene. RNA polymerase is now able to bind to the operator and promoter genes which also enables the transcription of the lacZ, lacY, and lacA genes.

• In the absence of glucose (disregard the presence or absence of lactose).

When there is no glucose, cAMP moves a catabolite activator protein (CAP) to the CAP site. This promotes the binding of RNA polymerase to the promoter and increases transcription.

• In the absence of glucose AND the presence of lactose.

When there is lactose and no glucose, the CAP/cAMP is bound to the CAP site and the repressor is removed from the operator (due to the presence of an inducer). This allows the lac genes to be expressed and high amounts of transcription to occur.

Finally, describe where in the process of gene expression (transcription, post-transcription, translation, post-translation) this regulation takes place.

The regulator is the repressor protein and regulation takes place at transcription. The repressor protein prevents the transcription process by physically blocking the RNA polymerase thus keeping the lac genes from being expressed. When the repressor is removed (via inducer) transcription begins and the genes are expressed.

Telomeres play a vital role in protecting our stored genetic information, so properly
understanding them can help us see how our DNA resists genomic rearrangements. The article, If
you want to live longer, take good care of your telomeres, gives a basic introduction of telomeres
and describes what their general purpose is. The author makes the comparison of aglets being
used to protect shoelaces with telomeres being used to protect DNA. They go on to describe that
a consequence of having telomeres that are too short is being susceptible to a cessation of cell
division. They also claim that short telomeres can lead an early onset of a “diseasespan” which
they describe as a period in one’s life when they become more at risk of disease and various
health problems (typically associated with old age).
The article written by Aubert and Lansdorp could be used to support the content in this
Washington Post article. While the article, Telomeres and Aging, makes no mention of a
“diseasespan”, it does conclude that “It seems plausible that, with age, the proliferation of an
increasing number of cells in normal individuals is compromised by progressive telomere loss.”
[2]. The article supports the notion that having short telomeres can “dire consequences”, but it
also makes note that telomere mechanisms play a role in limiting pre-cancer cells, as well as
other dysfunctional cells.
1.) Aubert, G. Lansdorp, P. M. Telomeres and Aging. Physiological Reviews;
https://doi.org/10.1152/physrev.00026.2007
2.) Hallett, V. If you want to live longer, take good care of your telomeres. Washington Post
Health-Science; https://www.washingtonpost.com/national/health-science/if-you-want-
to-live-longer-take-good-care-of-your-telomeres/2017/01/13/0127ab70-d69d-11e6-b8b2-
cb5164beba6b_story.html

Summary:
In the article, “Chromosome Folding Promotes Intrachromosomal Aberrations under Radiation- and
Nuclease-Induced DNA Breakage”, a “physical modeling” method for predicting genomic data from
chromosomes that been affected by ionizing radiation and the injection of nuclease is tested on chromosomes
collected from mice. Their aim was to test if physical modeling was capable of predicting results, and if the
outcome supported already established principles. The data used in their analysis of the chromosomal
aberrations was generated using conformation capture and translocation sequencing. The researchers attempted
to predict and model the chromosome structure and its aberrations which were induced by the aforementioned
ionizing radiation and nuclease injection. After analyzing their results, they found a quantitative link to their
predictions. Their key findings included organizational patterns of breakpoints in the experimental mice
chromosomes, a significant distance between the location of DNA double-strand breaks (caused by nuclease)
and a great amount of cis-translocation breakages. As well as chromosome contact maps. The article also stated
that their results supported a principle called the heteropolymer globule principle of chromosome organization.
The researchers also described how utilizing physical modeling in tandem with chromosome conformation
capture and translocation sequencing can offer a alternative way of looking at things cause radiation based
chromosomal aberrations such as: chromosome structure heterogeneity, globular folding and lesion dynamics
References:
Eidelman, Y., Salnikov, I., Slanina, S., Andreev, S. Chromosome Folding Promotes Intrachromosomal
Aberrations under Radiation- and Nuclease-Induced DNA Breakage. International journal of molecular
sciences 22, https://doi.org/10.3390/ijms222212186 (2021)

Wang J., Skeens E., Arantes P. R., Maschietto F., Allen B., Kyro G. W., Lisi G. P., Palermo G., Batista V. S. et al. Structural Basis for Reduced Dynamics of Three Engineered HNH Endonuclease Lys-to-Ala Mutants for the Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)-Associated 9 (CRISPR/Cas9) Enzyme. Biochemistry 61, https://pubs.acs.org/doi/10.1021/acs.biochem.2c00127 (2022)

A primary article is a source that analyses, or reports on, original results from an experiment. These
types of articles are usually written by the ones who conducted the experiment and are based on a firsthand experience with the results and the experimental procedure. The format of primary articles typically consists of five sections: the introduction, the methods, the results, the conclusion, and the references sections. The introduction gives background information regarding the experiment that was carried out. The methods describe the procedure that was followed and how it was carried out. The results relay the outcome of the experiment and visualize the results. The conclusion interprets and discusses the results. These articles are also reviewed by other experts in the same field to ensure their validity.
A review article describes, or analyzes, existing research described in primary articles. These types of
articles are usually used as a reference to give a general understanding of the topic of interest.
Once a researcher finishes their draft of the article containing their research, it is sent to be peer
reviewed. Peer reviewing an article is when other experts, of the same field of interest, review the article to
determine its validity and quality. They determine whether the article should be accepted, rejected, or revised by looking at whether or not the research is relevant, original, conducted in an appropriate manner, whether the findings are valid, etc. If the research article is approved by the reviewers, it is sent to an editor for a final approval or rejection.
The article Permanent Inactivation of Huntington’s Disease mutation is a primary article and the Huntington’s Disease Mechanisms is a review article. The Permanent Inactivation of Huntington’s Disease mutation article is formatted in the same way a primary article is typically formatted: it has an introduction, a materials and methods section, a results section, and a discussion section. Also, the information being presented is specific to one experiment. The Huntington’s Disease Mechanisms provides general background information regarding Huntington’s disease and is not specific to one experiment.

Kaden Koskovich
01/14/23
Genetics: CRN 30883
Curiosity is a powerful motivator, and it almost always starts with something small.
When I was younger, I wasn’t very scientific. It wasn’t until went to an archery range with my great uncle that curiosity was sparked. Admittedly, I was terrible. My uncle, on the other hand,
was much better and actually able to hit the target. This got me questioning: “Why was I doing so bad?”, “How was my uncle able to hit the target?”, and “What was stopping me?”. It was these small questions that ignited my curiosity, and it is my curiosity that continues to fuel me to this day.
As of now, I’ve been working as a pharmacy technician for the past four years. My
introduction into this career started in high school during my senior year. I had become curious about the “academy classes” which took place at different schools. One of the classes offered was a pharmacy technician training course. The idea of being able to learn about a variety of different medications, and their uses, intrigued me. However, there was one obstacle. This course had originally been set up to take place over the course of one year. This course, which was originally designed to be a one year course, was split into two sections. This meant the course would now take two years to complete which, as a senior, normally meant I would not be able to complete the course before graduating. I was determined to complete the course, so I requested to take both sections during my last year. My curiosity and determination paid off as I completed both sections and obtained my pharmacy technician certification.
Over the course of my pharmacy tech. career, I was given even more opportunities that
piqued my curiosity, especially during the start of the COVID-19 pandemic. I was introduced to Covid testing and eventually vaccinations as demand for such things increased. It was also
because of what I learned as a pharmacy technician that helped me decide on a major when
applying to ODU.
Now I study biochemistry with an eye on becoming a pharmacist. My goal is to
eventually apply the results of my curiosity while doing so in a way that will further fuel it.
Ever since I first started asking questions, my path became more and more scientific and
began to take the shape of medicine. I’ve become determined and even more curious, all because of something small.