Super Biology!

About Dolly

Dolly, a Finn Dorset sheep, was born on July 5th, 1996, at the Roslin Institute in Edinburgh, Scotland. Her birth, not revealed to the public until February 3rd, 1997, sparked controversy instantly, because Dolly was the world's first mammal to be cloned from an adult cell. Considered one of the most significant scientific breakthroughs ever, Dolly's birth and subsequent survival proved that adult cells can reprogram themselves into a new being. The team that created her, led by Scotsman Ian Wilmut, hoped to create an animal whose cells were genetically young again, rather than prematurely adult; however, when Dolly was reported to have been euthanased on February 14th, 2003, nearly six years after her birth, concern was raised that her progressive lung disease was caused because her cells were already old; she also had premature arthritis. Sheep can normally live to 11 or 12 years of age, and lung disease is not common in younger sheep. There was some speculation as to whether she caught it or not from the other sheep that she was housed with, but that claim has been neither confirmed nor denied.

Dolly, named after singer Dolly Parton, bred normally on two occasions, with a Welsh mountain ram named David, and over the course of her life gave birth to four lambs; proving thus that clones can reproduce. Francis Crick and James Watson are widely recognized as some of the first pioneers in cloning technology. Their discovery of the double-helix structure  of DNA in 1953, and later, their work on moecular heredity, helped to propel the science of biotechnology into the public view. This in turn led to an increase in scientific research that focused on learning the intricacies of the human genetic code and, subsequently, the discovery that cloning is possible and within reach of scientists today. Cloning as it exists today would probably not exist but for the research of these two men, who in 1962 received a Nobel prize for their work. Another important name in cloning history is John Gurdon, who in 1962 announced that he had used the nucleus of fully differentiated adult intestinal cells to clone South African frogs. Gurdon’s experiment was widely talked about, although it was never proven that the frogs were true clones.
In 1984, Steen Willadsun cloned a sheep from embryo cells, which were the predecessor to Dolly’s method of cloning. His work was the first verified incidence of cloning using nuclear transfer, which was remarkable at the time considering that only a few months earlier it had been said that it was biologically impossible.
The major debate over Dolly was the issue of subsequent human cloning. The ethics that need to be considered over this issue are enormous, and there is no one right answer.  Since Dolly, human cloning advocates have lobbied to legalize cloning; but so far this has not happened. Some people are of the opinion that cloning is essentially "playing God" and is abominable to say the least; they cite cloning experiments that have gone awry, with such results as deformed fetuses with oversized organs, and birthed animals that were twice the normal size and died soon after. Overall, the Dolly debate still continues internationally, and has never really died away. Whatever the future of cloning may be, Dolly existed, and that in itself is a momentous event in human history.

What is Cancer?

Cancer is a class of diseases characterized by out-of-control cell growth. There are over 100 different types of cancer, and each is classified by the type of cell that is initially affected.
Cancer harms the body when damaged cells divide uncontrollably to form lumps or masses of tissue called tumours (except in the case of leukemia where cancer prohibits normal blood function by abnormal cell division in the blood stream). Tumours can grow and interfere with the digestive, nervous, and circulatory systems, and they can release hormones that alter body function. Tumours that stay in one spot and demonstrate limited growth are generally considered to be benign.
  

 
More dangerous, or malignant, tumors form when two things occur:


1)a cancerous cell manages to move throughout the body using the blood or lymph systems, destroying healthy tissue in a process called invasion

 2)that cell manages to divide and grow, making new blood vessels to feed itself in a process called   angiogenesis.

When a tumour successfully spreads to other parts of the body and grows, invading and destroying other healthy tissues, it is said to have metastasized. This process itself is called metastasis, and the result is a serious condition that is very difficult to treat.

What Causes Cancer?

Cancer is ultimately the result of cells that uncontrollably grow and do not die. Normal cells in the body follow an orderly path of growth, division, and death.
Programmed cell death is called apoptosis, and when this process breaks down, cancer begins to form. Unlike regular cells, cancer cells do not experience programmatic death and instead continue to grow and divide.
This leads to a mass of abnormal cells that grows out of control.

What Are The Symptoms of Cancer?

Cancer symptoms are quite varied and depend on where the cancer is located, where it has spread, and how big the tumour is. Some cancers can be felt or seen through the skin - a lump on the breast or testicle can be an indicator of cancer in those locations. Skin cancer (melanoma) is often noted by a change in a wart or mole on the skin. Some oral cancers present white patches inside the mouth or white spots on the tongue.
 
Other cancers have symptoms that are less physically apparent. Some brain tumours tend to present symptoms early in the disease as they affect important cognitive functions. Pancreas cancers are usually too small to cause symptoms until they cause pain by pushing against nearby nerves or interfere with liver function to cause a yellowing of the skin and eyes called jaundice. Symptoms also can be created as a tumour grows and pushes against organs and blood vessels. For example, colon cancers lead to symptoms such as constipation, diarrhoea, and changes in stool size. Bladder or prostate cancers cause changes in bladder function such as more frequent or infrequent urination.
As cancer cells use the body's energy and interfere with normal hormone function, it is possible to present symptoms such as fever, fatigue, excessive sweating, anaemia, and unexplained weight loss. However, these symptoms are common in several other maladies as well. For example, coughing and hoarseness can point to lung or throat cancer as well as several other conditions.
When cancer spreads, or metastasizes, additional symptoms can present themselves in the newly affected area. Swollen or enlarged lymph nodes are common and likely to be present early. If cancer spreads to the brain, patients may experience vertigo, headaches, or seizures. Spreading to the lungs may cause coughing and shortness of breath. In addition, the liver may become enlarged and cause jaundice and bones can become painful, brittle, and break easily. Symptoms of metastasis ultimately depend on the location to which the cancer has spread.

How Cancer Can Be Prevented

Cancers that are closely linked to certain behaviours are the easiest to prevent. For example, choosing not to smoke tobacco or drink alcohol significantly lower the risk of several types of cancer - most notably lung, throat, mouth, and liver cancer. Even if you are a current tobacco user, quitting can still greatly reduce your chances of getting cancer.
 
Skin cancer can be prevented by staying in the shade, protecting yourself with a hat and shirt when in the sun, and using sunscreen. Diet is also an important part of cancer prevention since what we eat has been linked to the disease. Physicians recommend diets that are low in fat and rich in fresh fruits and vegetables and whole grains.
 
Certain vaccinations have been associated with the prevention of some cancers. For example, many women receive a vaccination for the human papillomavirus because of the virus's relationship with cervical cancer. Hepatitis B vaccines prevent the hepatitis B virus, which can cause liver cancer.
Some cancer prevention is based on systematic screening in order to detect small irregularities or tumours as early as possible even if there are no clear symptoms present. Breast self-examination, mammograms, testicular self-examination, and Pap smears are common screening methods for various cancers.

Researchers from North Western University Feinberg School of Medicine in Chicago reported in the journal Circulation that the 7 steps recommended for protection against heart disease can also reduce the risk of developing cancer,. They include being physically active, eating a healthy diet, controlling cholesterol, managing blood pressure, reducing blood sugar and not smoking

Digestion

Digestion is the complex process of turning the food you eat into the energy you need to survive. The digestion process also involves creating waste to be eliminated.
The digestive tract (or gut) is a long twisting tube that starts at the mouth and ends at the anus. It is made up of a series of muscles that coordinate the movement of food and other cells that produce enzymes and hormones to aid in the breakdown of food. Along the way are three other organs that are needed for digestion: the liver, gallbladder, and the pancreas.

Food's Journey Through the Digestive System

Stop 1: The Mouth
The mouth is the beginning of the digestive system, and, in fact, digestion starts here before you even take the first bite of a meal. The smell of food triggers the salivary glands in your mouth to secrete saliva, causing your mouth to water. When you actually taste the food, saliva increases.
Once you start chewing and breaking the food down into pieces small enough to be digested, other mechanisms come into play. More saliva is produced to begin the process of breaking down food into a form your body can absorb and use. In addition, "juices" are produced that will help to further break down food. Chew your food more -- it helps with your digestion.

Stop 2: The Pharynx and Esophagus
Also called the throat, the pharynx is the portion of the digestive tract that receives the food from your mouth. Branching off the pharynx is the esophagus, which carries food to the stomach, and the trachea or windpipe, which carries air to the lungs.
The act of swallowing takes place in the pharynx partly as a reflex and partly under voluntary control. The tongue and soft palate -- the soft part of the roof of the mouth -- push food into the pharynx, which closes off the trachea. The food then enters the esophagus.
The esophagus is a muscular tube extending from the pharynx and behind the trachea to the stomach. Food is pushed through the esophagus and into the stomach by means of a series of contractions called peristalsis.
Just before the opening to the stomach is an important ring-shaped muscle called the lower esophageal sphincter (LES). This sphincter opens to let food pass into the stomach and closes to keep it there. If your LES doesn't work properly, you may suffer from a condition called GERD, or reflux, which causes heartburn and regurgitation (the feeling of food coming back up).

Stop 3: The Stomach and Small Intestine
The stomach is a sac-like organ with strong muscular walls. In addition to holding food, it serves as the mixer and grinder of food. The stomach secretes acid and powerful enzymes that continue the process of breaking the food down and changing it to a consistency of liquid or paste. From there, food moves to the small intestine. Between meals, the non-liquefiable remnants are released from the stomach and ushered through the rest of the intestines to be eliminated.
Made up of three segments -- the duodenum, jejunum, and ileum -- the small intestine also breaks down food using enzymes released by the pancreas and bile from the liver. The small intestine is the 'work horse' of digestion, as this is where most nutrients are absorbed. Peristalsis is also at work in this organ, moving food through and mixing it up with the digestive secretions from the pancreas and liver, including bile. The duodenum is largely responsible for the continuing breakdown process, with the jejunum and ileum being mainly responsible for absorption of nutrients into the bloodstream.
A more technical name for this part of the process is "motility," because it involves moving or emptying food particles from one part to the next. This process is highly dependent on the activity of a large network of nerves, hormones, and muscles. Problems with any of these components can cause a variety of conditions.
While food is in the small intestine, nutrients are absorbed through the walls and into the bloodstream. What's leftover (the waste) moves into the large intestine (large bowel or colon).
Everything above the large intestine is called the upper GI tract. Everything below is the lower GI tract.

Stop 4: The Colon, Rectum, and Anus
The colon (large intestine) is a five- to seven -foot -long muscular tube that connects the small intestine to the rectum. It is made up of the ascending (right) colon, the transverse (across) colon, the descending (left) colon and the sigmoid colon, which connects to the rectum. The appendix is a small tube attached to the ascending colon. The large intestine is a highly specialized organ that is responsible for processing waste so that defecation (excretion of waste) is easy and convenient.
Stool, or waste left over from the digestive process, passes through the colon by means of peristalsis, first in a liquid state and ultimately in solid form. As stool passes through the colon, any remaining water is absorbed. Stool is stored in the sigmoid (S-shaped) colon until a "mass movement" empties it into the rectum, usually once or twice a day.
It normally takes about 36 hours for stool to get through the colon. The stool itself is mostly food debris and bacteria. These bacteria perform several useful functions, such as synthesizing various vitamins, processing waste products and food particles, and protecting against harmful bacteria. When the descending colon becomes full of stool, it empties its contents into the rectum to begin the process of elimination.

The rectum is an eight-inch chamber that connects the colon to the anus. The rectum:

• Receives stool from the colon
• Lets the person know there is stool to be evacuated
• Holds the stool until evacuation happens

When anything (gas or stool) comes into the rectum, sensors send a message to the brain. The brain then decides if the rectal contents can be released or not. If they can, the sphincters relax and the rectum contracts, expelling its contents. If the contents cannot be expelled, the sphincters contract and the rectum accommodates so that the sensation temporarily goes away.
The anus is the last part of the digestive tract. It consists of the muscles that line the pelvis (pelvic floor muscles) and two other muscles called anal sphincters (internal and external).
The pelvic floor muscle creates an angle between the rectum and the anus that stops stool from coming out when it is not supposed to. The anal sphincters provide fine control of stool. The internal sphincter is always tight, except when stool enters the rectum. It keeps us continent (not releasing stool) when we are asleep or otherwise unaware of the presence of stool. When we get an urge to defecate (go to the bathroom), we rely on our external sphincter to keep the stool in until we can get to the toilet.

Osmosis

Large quantities of water molecules constantly move across cell membranes by simple diffusion, but, in general, net movement of water into or out of cells is negligible. For example, it has been estimated that an amount of water equivalent to roughly 250 times the volume of the cell diffuses across the red blood cell membrane every second; the cell doesn't lose or gain water because equal amounts go in and out.
There are, however, many cases in which net flow of water occurs across cell membranes and sheets of cells. An example of great importance to you is the secretion of and absorption of water in your small intestine. In such situations, water still moves across membranes by simple diffusion, but the process is important enough to warrant a distinct name - osmosis.
Osmosis is the net movement of water across a selectively permeable membrane driven by a difference in solute concentrations on the two sides of the membrane. A selectively permeable membrane is one that allows unrestricted passage of water, but not solute molecules or ions.
Different concentrations of solute molecules leads to different concentrations of free water molecules on either side of the membrane. On the side of the membrane with higher free water concentration (i.e. a lower concentration of solute), more water molecules will strike the pores in the membrane in a give interval of time. More strikes equates to more molecules passing through the pores, which in turn results in net diffusion of water from the compartment with high concentration of free water to that with low concentration of free water.
The key to remember about osmosis is that water flows from the solution with the lower solute concentration into the solution with higher solute concentration. This means that water flows in response to differences in molarity across a membrane. The size of the solute particles does not influence osmosis. Equilibrium is reached once sufficient water has moved to equalize the solute concentration on both sides of the membrane, and at that point, net flow of water ceases. Here is a simple example to illustrate these principles:

Two containers of equal volume are separated by a membrane that allows free passage of water, but totally restricts passage of solute molecules. Solution A has 3 molecules of the protein albumin (molecular weight 66,000) and Solution B contains 15 molecules of glucose (molecular weight 180). Into which compartment will water flow, or will there be no net movement of water?

Additional examples of how to determine which direction water will flow in different circumstances are provided. When thinking about osmosis, we are always comparing solute concentrations between two solutions, and some standard terminology is commonly used to describe these differences:

Isotonic: The solutions being compared have equal concentration of solutes. Hypertonic: The solution with the higher concentration of solutes. Hypotonic: The solution with the lower concentration of solutes.

In the examples above, Solutions A and B are isotonic (with each other), Solutions A and B are both hypertonic compared to Solution C, and Solution C is hypotonic relative to Solutions A and B. Diffusion of water across a membrane - osmosis - generates a pressure called osmotic pressure. If the pressure in the compartment into which water is flowing is raised to the equivalent of the osmotic pressure, movement of water will stop. This pressure is often called hydrostatic ('water-stopping') pressure. The term osmolarity is used to describe the number of solute particles in a volume of fluid. Osmoles are used to describe the concentration in terms of number of particles - a 1 osmolar solution contains 1 mole of osmotically-active particles (molecules and ions) per liter. You can investigate these principles further using an osmosis and hydrostatic pressure simulator. The classic demonstration of osmosis and osmotic pressure is to immerse red blood cells in solutions of varying osmolarity and watch what happens. Blood serum is isotonic with respect to the cytoplasm, and red cells in that solution assume the shape of a biconcave disk. To prepare the images shown below, red cells from your intrepid author were suspended in three types of solutions: Isotonic - the cells were diluted in serum: Note the beautiful biconcave shape of the cells as they circulate in blood. Hypotonic - the cells in serum were diluted in water: At 200 milliosmols (mOs), the cells are visibly swollen and have lost their biconcave shape, and at 100 mOs, most have swollen so much that they have ruptured, leaving what are called red blood cell ghosts. In a hypotonic solution, water rushes into cells. Hypertonic - A concentrated solution of NaCl was mixed with the cells and serum to increase osmolarity: At 400 mOs and especially at 500 mOs, water has flowed out of the cells, causing them to collapse and assume the spiky appearance you see.