Core Biology Students Gel Electrophoresis (DNA analysis)

          Of the three billion nucleotides in human DNA, more than 99% are identical among individuals. The remaining 1%, however, adds up to a significant amount of code variations between individuals, making each person's DNA profile as unique as a fingerprint. Due to the large number of possible variations, no two people (with the exception of identical twins) have the same DNA sequence.

          For every 1,000 nucleotides inherited, there is one site of variation, or polymorphism. DNA polymorphisms change the length of the DNA fragments produced by the digestion of restriction enzymes, so the exact number and size of fragments produced by a specific restriction enzyme digestion varies from person to person. The resulting fragments, called Restriction Fragment Length Polymorphisms (RFLPs), can be separated, and their size determined, by electrophoresis.

          Most of the DNA in a chromosome is not used for the genetic code; it is uncertain what, if any, use this DNA may have. Because these regions are not essential to an organism's development, it is more likely that changes will be found in these nonessential regions. The regions that contain nucleotide sequences that repeat from 20 to 100 times (e.g., GTCAGTCAGTCAGTCA) are the strands cut by restriction enzymes to create RFLPs.

          The difference in the fragments can be quantified to create a "DNA fingerprint". Distinct RFLP patterns can be used to trace the inheritance of chromosomal regions with genetic disorders or to identify the origin of a blood sample in a criminal investigation. Scientists have identified more than 3,000 RFLPs in the human genetic code, many of which are highly variable among individuals. It is this large number of variable yet identifiable factors that allows scientists to identify individuals by the number and size of their various RFLPs.

          This technique is being used more and more frequently in legal matters. Using DNA fingerprinting, the identity of a person who has committed a violent crime can be determined from minute quantities of DNA left at the scene of the crime in the form of blood, semen, hair, or saliva. The DNA fingerprint matched to a suspect can be accurate to within one in 10 billion people, which is almost twice the total population in the world. Certain limitations in the technique prevent two samples from being identified as a "perfect match", yet it is possible to measure the statistical probability of two samples coming from the same individual based on the number of known RFLPs that exist in a given population.

          DNA fingerprinting has many other applications, since half of a person's genome comes from each parent, DNA fingerprinting can be used to determine familial relationships. It has a much higher certainty than a blood test when used to determine fatherhood in a paternity suit. DNA fingerprinting can be used to track hereditary diseases passed down family lines, as well as to find the closest possible matches for organ transplants. It can also be used to ascertain the level of inbreeding of endangered animals, aiding in the development of breeding programs to increase animals' genetic health and diversity.

Students use micropipettes to load their samples into agar rose gels

The gels are placed in the electrophoresis apparatus and submerged in a buffer. Once this is done the micropipette is used to load the wells in the gel

Core Earth Science Students Model Impact Craters

Impact craters are geologic structures formed when a large meteoroid, asteroid or comet smashes into a planet or a satellite. All the inner bodies in our solar system have been heavily bombarded by meteoroids throughout their history. The surfaces of the Moon, Mars and Mercury, where other geologic processes stopped millions of years ago, record this bombardment clearly. On the Earth, however, which has been even more heavily impacted than the Moon, craters are  continually erased by erosion and redeposition as well as by volcanic resurfacing and tectonic activity. Thus only about 120 terrestrial impact craters have been recognized, the majority in geologically stable craters of North America, Europe and Australia where most exploration has taken place. Spacecraft orbital imagery has helped to identify structures in more remote locations for further investigation.

Meteor Crater (also know as Barringer Crater) in Arizona was the first-recognized terrestrial impact crater, currently 170 impact craters have been identified on the Earth.

The students were using six different types of projectiles to form their impact craters. They dropped them from different heights, calculated their kinetic energies, made measurements of diameter and depth of the craters.  They will use this data to compare the craters formed by different projectiles.

Construction papers are used to try to capture the rays formed by the materials that are thrown out of the point of impact.

Crater with its "projectile" still intact. The projectiles used were of different sizes and made of materials with different masses.

Matt D. Vivian M. Danny G and Xiao H. are obviously enjoying the controlled destruction they can mete out to their model planet surface. You can see some of the varied "projectiles" in the weighing cup on the lab table.

Brendan W. and Jack M. are carefully removing the "projectile" before measuring its dimensions

Core Biology Class Studies Yeast Respiration Rates

Mrs. Bastone's students in Core Biology are using the Labquest2 tablets and carbon dioxide probes to measure the respiration rate of yeast suspensions, They will be comparing the rates using 10% solutions of various sugars (maltose, lactose, sucrose and glucose). The probes and tablets have simplified the collection and analysis of data, enabling student to e-mail the graphs of their data home, however they are still getting error messages when they attempt to e-mail their data files home.

The students mixed 5 ml of a yeast suspension with 5 ml of a 10% sugar solution in the reaction bottle. They then insert the carbon dioxide probe which will measure the amount of carbon dioxide gas in the bottle every 5 seconds for a 10 minute period of time.

Once the students have completed their data collection, the tablet can analyze their data by drawing the best fit line.

This lab group has activated the WiFi feature which delivers the graph being produced from the data collected by the probe simultaneously to their mobile devices.

The tablet is graphing the data collected with the carbon dioxide produced in parts per million over time. The linear regression analysis when data collection is completed will identify the slope of the resulting line. The slope will give the students the respiration rate for the yeast suspension.

Bronxville Research Students present at the Junior Science and Humanities Competition

Two students from Bronxville HS competed in the Junior Science and Humanities Competition at John Jay High School in Cross River this past Saturday Feb 2 and both did very well!

Senior Jackie Faselt presented her project on "Speeding up Solar Water Disinfection" as a speaker and came in 5th out of over 100 senior speakers; she is now an alternate to go on to the state competition in Albany in March.

Jackie discussing her research into SODIS techniques and their use in water purification this past June at Bronxville's Third Annual Science Research Fair/Ezposition .

Junior Elizabeth McGough's poster presentation of her research "Sound improves Appetitive Olfactory Conditioning in Drosophila melanogaster"  came in third in her category of Animal and Environmental Science! Kudos to both!

Elizabeth discussing her work on the effects of olfactory and auditory stimuli on the operant conditioning (learning) in Drosophilia this past June at Bronxville's Third Annual Science Research Fair/Exposition