What is the only remaining wonder of the ancient world that is still standing?
The Great Pyramid at Giza
Unlike the list of natural wonders, the seven wonders of the ancient world are man-made structures that serve as a testament to the ingenuity, imagination, and hard work of which human beings are capable. At its inception, the sites were not “wonders” but “theamata” or “things to be seen”. The collection was more like a Greek travel guide’s idea of places not to be missed. The definitive set of wonders is believed to have been finalized during the Middle Ages.
Of the seven, just one remains to this day: the Great Pyramid at Giza. The last wonder of the ancient world in existence was also the first one built. The pyramid was built as a tomb for Egyptian Pharaoh Khufu around 2560 B.C. It took 20 years to construct. When finished, it stood 480 feet high and remained the tallest building in the world for the next four thousand years.
The Great Pyramid at Giza and the others standing with it have stood for four and a half thousand years and counting.
What wonder of the ancient world stood the least amount of time?
The Colossus at Rhodes
The Colossus at Rhodes was an enormous looming 100-foot bronze statue that was built on the island of Rhodes around 280 B.C. It depicts the island’s patron god, Greek sun god Helios.
No drawings of the statue survive but it has been described as an upright figure with face mostly likely modeled after Alexander the Great, holding a torch not unlike the Statue of Liberty.
It was long believed that the statue straddled the harbor entrance with ships passing in and out between its legs. Modern archeologists say this would have not been possible with the bronze casting techniques available at the time.
The statue was destroyed in 226 B.C., after a mere 54 years.
How was the Colossus of Rhodes destroyed?
The Colossus was built between 292 and 280 B.C. and was placed at the entrance to the harbor of the Greek Island of Rhodes. The statue stood 98 feet tall and was erected to honor their patron god, Helios.
Rhodes experienced an earthquake in 224 B.C. that broke the Colossus at the knees and toppled the top portion to the ground. People believed Helios was angered by the statue and did not rebuild it.
Even broken, the pieces were impressive. For the next 900 years, the ruins lay on the ground attracting visitors from all over the world. Few people could wrap their arms around the fallen thumb and each of its fingers was larger than most statues.
In 654 A.D., Arabs conquered Rhodes, transported the remains to Syria, and most likely melted them down and sold them for scrap metal.
What wonder of the ancient world may never have existed at all?
The Hanging Gardens of Babylon
The Hanging Gardens were said to have been built ~600 B.C. in the Babylon province of Iraq, south of Bagdad. There is no existing Babylonian text that mentions the gardens and no definitive archeological evidence has been found for them.
According to the legend, King Nebuchadnezzar built the gardens for his wife because she missed the green hills and valleys of her homeland. He built a man-made mountain with lush vegetation and cascading waterfalls. Plants high above the ground on multi-stone terraces gave the appearance of hanging. Stone pillars supported high walkways.
The Hanging Gardens would certainly have been a marvel of engineering and construction, but did they exist?
A researcher at Oxford University says yes! Dr. Stephanie Dalley believes that we had the location wrong. The Hanging Gardens may never have been in Babylon but instead 300 miles to the north outside the city of Nineveh. Ancient texts describe the life of the great Assyrian ruler, Sennacherib, with detailed descriptions of his palace and his garden with trees hanging in air.
The location proposed by Dr. Dalley as the correct site of the Hanging Gardens is near Mosul in Iraq. Because it is at this time the site of continuing violence, it is unsafe for archeological work. The destruction during the current wars and the pillaging over the years may erase any trace of an ancient hanging garden.
What ancient wonder was built in honor of the Olympic games?
The Statue of Zeus
A massive gold statue honoring the king of all Greek gods, Zeus, was built around 432 BC in Olympia, the site of the first Olympic games. The figure sat on a jewel-encrusted throne inside a temple overlooking the city.
In 391 AD, the Olympics were banned as a pagan practice and the temple was closed after Christianity had become the official religion of the Roman Empire.
The statue was eventually destroyed but historians debate whether it perished with the temple or was moved to Constantinople and burned in a fire.
The complete list of ancient wonders is: The Great Pyramid at Giza, Statue of Zeus at Olympia, Colossus of Rhodes, Lighthouse at Alexandra, Mausoleum at Halicarnassus, Temple of Artemis at Ephesus, and the Hanging Gardens at Babylon
What is an organism’s complete set of DNA called?
A genome is an organism’s complete set of DNA including all its genes. Each genome contains all the information needed to build and maintain that organism.
In humans, a copy of the entire genome is contained in all cells that have a nucleus.
The typical human body has an estimated 25,000 genes and has an enormous amount of DNA that does not code for RNA or protein. Managing so much DNA requires that the genome be elaborately organized and compact.
DNA wraps around proteins called histones, and together they make chromatin.
Why doesn’t chromatin fall apart?
The attraction between the negatively-charged DNA and the positively-charged histones binds them tightly together.
Every cell in a human body has the exact same DNA and yet they make different organs. The protein coding part of the genome, called genes, do not make proteins all the time in all of the cells. Sections of DNA are marked, signaling which genes to ignore and which to use.
Chromatin can open and close. If a region is open, that area is turned “on” and protein can be made. If a region is closed, that area is being prevented from being turned on.
What do we call the collection of chemical compounds that modify, or mark, the genome that tells it what to do, where to do it, and when to do it?
Our genome is something we are born with and cannot modify. Our epigenome contains "instructions" on how to use the genome. “Epi” comes from the Greek word “above”.
These are small chemical modifications on histones or DNA that give instructions on how to "read" and "use" our genes. Like traffic lights.
A gene that is turned "on" is producing protein so we call it an “active gene". One that is turned "off" is not producing protein and is called a "silent gene".
Some genes are always active (housekeeping genes), some genes are active only at certain times in the development of an organism (developmental genes), some genes are active only in certain tissues like the heart or eye (tissue-specific genes), while some genes are being turned on and off many times.
The pattern of activity of certain genes (the epigenome) is inherited from your parents (just like the genome), but it is also very susceptible to influences from the environment.
Who proposed the Law of Inheritance of Acquired Characteristics?
Throughout the years, the French naturalist Lamarck has gone in and out of favor. Lamarck understood that all species are descended from a common ancestor and he was the first person to propose a cohesive evolutionary theory of how a species mutated over time, a theory that paralleled Charles Darwin’s.
He believed that an organism could pass on characteristics that it acquired during its lifetime to its offspring.
During Lamarck’s life (1744-1829), his ideas were not respected. He died in obscurity and poverty.
In the mid-19th century, his Law of Inheritance of Acquired Characteristics was rediscovered but fell out of favor in the early 20th century when Mendel’s work with genes was finally understood.
Interest in Lamarck’s ideas has resurfaced as studies in the epigenetic field have highlighted the possible inheritance of behavioral traits acquired by the previous generation.
What is that part of the cell cycle when the nucleus divides?
The continuity of life is based on cell division. After an organism is completely grown, cell division continues to function in renewal and repair.
In preparation for cell division, DNA duplicates itself. After duplication, the chromatin fibers coil, fold, and are packed into chromosomes. Each chromosome has two sister chromatids.
During mitosis, the cytoskeleton disappears and the nuclear envelope breaks down. Chromosomes move to the equator and line up. Proteins holding the chromosomes together break down and each chromosome is pulled to opposite ends of the cell.
The chromosomes disassemble and the nuclear envelope reforms. The division of the cytoplasm usually follows immediately after mitosis, and cell division is complete.
In its condensed form, a chromosome has a narrow “waist” where the sister chromatids are closely attached. What is this area called?
The centromere is a constricted area to which specialized molecules called spindle fibers attach and help pull daughter cells apart during cell division.
Investigators have known for many years that cell division is controlled by epigenetic processes rather than encoded in the DNA itself. Epigenetics mark the place where spindle fibers attach to the chromosome independent of the underlying DNA sequence. Researchers have suspected the crucial epigenetic marker protein is the CENP-A molecule, which defines part of the centromere.
Ben Black and his lab have described the structure of CENP-A. The Black lab gave the first high-resolution view of the CENP-A molecule and described the structural features that confer the CENP-A the ability to mark centromere location.
The understanding of CENP-A and the epigenetics associated with cell division help advance the science of human inheritance.
Next week's question:
How many chromosomes are in a single cell in the human body?