AP Biology class blog for discussing current research in Biology

Tag: Chromosome

23 Chromosomes. One Unique You.

This weekend, my parents told me we were trying a new product from a company called 23andme. When I first saw the words ”Welcome to you, DNA Collection Kit” written on the box, I thought it was another one of my Dad’s SkyMall purchases that is thrown away a week after buying it. This one was more intriguing than most, so I decided to investigate on-line. I am amazed that he actually purchased something of use.

23andme is a new company that analyzes your DNA and compares it to millions of others to determine your unique traits. While human DNA is about 99.5% identical between people, there are small differences called variants. These variants come from your parents, your parent’s parents, and so on. Within a month of submitting your DNA, I will get results that will tell me a number of things relating to my genetic make-up including possible health conditions that I have now or will get in the future, traits and my ancestry groups. I can’t wait.

To start the process, 23andme provides a tube with instructions. I had to spit inside the tube and my saliva was mixed with a clear liquid when I sealed the tube.  The tube is then shipped to 23andme, where they will take the saliva sample and extract and process the DNA on a genotyping chip that reads hundreds of thousands of variants in your genome. Genotyping is a method to extract and analyze the DNA found in your saliva. The lab will read the variants in my DNA versus other people’s DNA and generate personalized reports based on well-established scientific and medical research.

I’m pretty nervous about what the DNA test will tell me!

First, I will learn about my ancestry – where did I come from? What percent of my ancestry is European and what percent is Cuban? Who are my relatives? Is Yoenis Cespedes my real father? All of these questions will be answered along with contact information for my DNA relatives around the world- I think this means season tickets too!

Secondly, I will find out if I am a carrier for certain inherited conditions. Being a carrier means I have the variant for a condition which I can pass down, but I don’t have the condition. This is where potential controversies arise because people may or may not want to know if they are carriers  for harmful diseases. I am not sure I want to know! They test for over 35 conditions.

Thirdly, I will get a report that explains how my DNA impacts my health and my traits. Some of these include hair color, my chances of having a unibrow,  if I’m going to go bald (and when!), and if I have a preference for sweet vs. salty foods (I actually like both so good luck with that!).

I’m particularly excited for my results because I was born with a syndrome called Beckwith-Wiedemann syndrome, which results from the abnormal regulation of genes in a certain region of chromosome 11. I’m very interested to see if they are able to tell me more about this syndrome.

As 23andme gets more popular, there will be more data to compare with, which will expand the limits of what we can find out! I can not wait to meet all of my DNA relatives. Results will be in by the end of November, hopefully just in time for bring your Father to school day!




Can We “Turn Off” a Chromosome?

What is this crazy idea of “turning off” a chromosome and how will it benefit us? Well, in a recent scientific discovery Dr.Jeanne Lawrence and her team found a way to turn off the extra chromosome that causes Down syndrome. This discovery talked about in an article written by Jennifer Wong has opened new perspectives on treating the syndrome. Now now, this is not a cure to Down syndrome, it is way to eliminate the symptoms. Still an astonishing feat! To examine this we must first simply look at what Down syndrome is. Down syndrome is caused by the presence of an extra chromosome- chromosome 21. So we can fully understand chromosome 21 in it’s entirety is here is some more information. People unaffected by this syndrome have 22 chromosomes, however in the case of Down syndrome chromosome 21 gets copied three times instead of the regular two- causing an extra chromosome. This genetic disorder is quite common in our present day. Down syndrome is known for causing intellectual issues, heart problems and early Alzheimer’s disease. To add, this is a great website which explains Down syndrome in further detail.


The extra chromosome 21 in down syndrome

The extra chromosome 21 in down syndrome

So what is this ground breaking discovery? Dr.Lawrence, at the University of Massachusetts, tested the idea of “shutting  down” chromosome 21. She and her team had discovered that the gene specifically involved with X-Chromosome  inactivation could be used to “turn off” the extra chromosome. This gene is known as XIST- X-inactive specific transcript. XIST has a non-coding RNA covering. This causes a string of chromosomal changes that mute gene expression. Dr.Lawrence wondered if this gene could be used to shut down chromosome 21. She and her team set up an experiment- to insert the XIST gene into the extra chromosome and see if it causes the inactivation they were hoping for. But doing so is not as simple as it sounds. How do we insert a gene into a chromosome with out fault? The answer to this is an editing enzyme called the zinc finger nuclease- an enzyme that can insert genes into chromosomes while making little to no mistake. To  ensure certainty  the team used doxycycline, a drug that helped to induce an expression from the gene.

After conducting this experiment Dr.Lawrence and her team found that the expression induced by the doxycycline on the XIST gene could effectively inactivate or in other words, turn off, the extra chromosome. This turned it into a Barr body (a condensed X chromosome). The experiment had worked! Dr.Lawrence’s paper on the experiment can be found here. The inactivation of chromosome 21 eliminated the symptoms of Down syndrome. A brilliant discovery sure to pave the way for further exploration of cures to Down syndrome, a syndrome which effects many people in our world today. What do you think of this amazing find and how it will benefit those affected by Down syndrome?

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Telomere the Tell all?

Scientists have recently discovered that they can predict life expectancy based on the length of the telomere in patients with heart disease. Telomeres which are protective, non coding regions at the ends of chromosomes get shorter over time due to cell division. The replication of DNA shortens our telomeres and our chromosomes. This makes us more susceptible to age-related “diseases such as heart disease or cancer, as well as exposure to oxidative damage from stress, smoking, air pollution, or conditions that accelerate biologic aging.” ( length used to be used to show age in a person but recently it also seems to be correlated with their chance of survival with heart disease. In a study conducted with 3,500 heart attack and stroke patients, researchers stated that those with longer telomeres had a greater chance of survival. In the future doctors believe that judging from the telomeres in patients, they could increase their effectiveness in treating heart disease.

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