Not alive? That won’t stop it from trying to kill you.

Although one of these complicated and non-living “things” does like to eat your brain, I’m actually not referring to zombies. With the exception of viroids, which are made entirely of a short strand of RNA, Viruses, retroviruses, and prions are all made up of proteins and can’t reproduce on their own, which is why they aren’t technically considered to be “alive.” Since they can’t reproduce they have use other cells or proteins to do all the replicating for them, making them responsible for many diseases; from something annoying but generally harmless like the common cold, to something far more sinister and often fatal like AIDS and mad cow disease. Let’s have a look:

Viruses are very, very small; even smaller than bacteria, and their genome (which can be either DNA or RNA) is contained inside of a protein capsid. Viruses use a host cell to reproduce more viruses for them, which is done by the virus attaching itself to a particular cell and injecting its genetic material into either the machinery of the host cell, or directly into its genome. The cell is then either destroyed immediately after the creation of new viruses, or continues its own replication process as usual, unaware to the existence of foreign genetic material encoded within its DNA, before eventually being destroyed as well. The reason viruses cause disease is that the infected cell cannot carry out the normal functions necessary because its machinery is being used by the virus, which eventually results in the death of the cell.

There are many different types of viruses, for example, a bacteriophage which is a virus that only goes after bacteria. Another more serious class of virus is the retrovirus. These use a single strand of RNA, which can cause an incredible amount of damage as it is used as a template for the creation of new infected DNA strands within the cell. Retroviruses are known to be the cause of leukemia, tumors in practically any part of the body, and AIDS.

Viroids are even smaller and are often carried around within viruses. They do not have a protein capsid, and solely consist of a short strand of RNA. They are usually only ever found in plants and self-replicate using the cell’s enzymes, which may interfere with the plant’s growth cycle.

Prions on the other hand contain no nucleic acid whatsoever, as they are simply a certain type of misfolded protein. The word ‘prion’ is derived from ‘proteinaceous infectious particle’ which is a very accurate name, seeing as they like to ‘infect’ or change other proteins, causing them to also miss fold. These misfolded proteins are extremely stable, meaning that they cannot be easily destroyed. As they multiply they require more and more space, resulting in the death of surrounding cells. In the brain this results in the creation of holes in the brain tissue, which in turn results in the deterioration of the organism’s mental and physical abilities. This is known as Transmissible Spongiform Encephalopathy in humans, and Bovine Spongiform Encephalopathy (or more commonly as simply Mad Cow disease) in cows.

All of these non-living entities have an odd way of mimicking life in order to get what they want, and there is no known cure for most of the diseases that they cause. Scientists are working to learn more, but in the meantime, rather than preparing for a zombie apocalypse, perhaps you should instead avoid eating meat from cows with Bovine Spongiform Encephalopathy.

Why Men are Far More Likely than Women to Be Colorblind

Colorblindness is a recessive sex-linked trait, meaning that it is found only on X chromosomes. It is fairly uncommon, and since it is an inherited disorder it can only appear when two heterozygous parents (meaning that they carry both dominant and recessive genes) each contribute recessive alleles, meaning that the baby will be a girl; or if the father contributes a Y chromosome, resulting in the creation of a boy. Here’s why:

Females carry two X chromosomes, and males carry only one X chromosome, as well as a Y chromosome. The sex of a child is determined by which chromosomes the parents contribute. The mother can only contribute X chromosomes, so the sex of a human being is ultimately determined by the father. If he contributes an X, the child will have two X chromosomes, meaning that it will be a girl; but if the father contributes a Y chromosome, the child will have both X and Y chromosomes and will be a boy.

Y chromosomes don’t carry a whole lot of genetic information, and the trait for colorblindness is only found on the X chromosome. This means that if the mother contributes an X chromosome carrying the recessive allele for colorblindness, and the father contributes a Y chromosome (Y chromosomes don’t carry any dominant or recessive alleles), then there will be no dominant allele to mask the colorblind gene, and the resulting boy will be colorblind. The only way for a girl to be colorblind is if both of her parents are already colorblind (which is highly unlikely), or if her father is colorblind and her mother is a carrier. Even then, there is still a fifty-fifty chance as to whether or not she will inherit the defective allele. This is why men are far more likely to inherit this trait than women. If the mother passes on a defective allele, and the father passes on a Y chromosome, there simply is no way to avoid the creation of a colorblind boy.

Injuries & Cell Mitosis

You scrape your knee so deeply that it bleeds. Later a scab forms over the wound. When the scab falls off, you have new skin underneath. Where did the new skin come from? Describe the process in detail.

When you cut yourself, skin cells are unceremoniously removed from the affected area, exposing and breaking the underlying blood vessels. In order to heal the wound, the blood starts to clot, forming a plug which prevents more blood from flowing out. This eventually creates a scab, which in turn protects the area so the underlying skin cells can heal properly. [kidshealth.org]

The skin cells around the edge of the wound begin to divide, creating more and more cells until the wound is completely covered with new skin. Cell division (or mitosis) is when a healthy cell divides, making two new genetically identical “daughter” cells.

Mitosis begins when the cell reaches what biologists refer to as the “S phase” of its life cycle. During this phase, the cell begins to replicate its DNA, creating two chromatids (two copies of DNA chromosomes stuck together). These double chromosomes are packed into dense coils and attached together by a centromere. Certain proteins also begin to move into place, starting to form a long chain of microtubules called a “spindle,” which is in turn attached to two complex sets of proteins called centrosomes. This is all part of what is known as the prophase of mitosis. Next, during the metaphase, the chromatids line up at the center of the cell, along a sort of “equator.” The spindles are attached to the chromatids, and the centrosomes are pulled in opposite directions, forming something resembling a North and South Pole. The next phase of mitosis, called the anaphase, is when the spindle –with the help of motor proteins- begins to shorten, pulling apart the chromatids and elongating the cell. This leads into the final phase of mitosis: the telophase. During this phase, the cell continues to stretch until it is pulled apart, each side containing its own set of chromosomes. A new nucleus is formed within each cell, as well as a nuclear envelope, which protects both the nucleus and the chromosomes.  Mitosis is complete; Cytokinesis (meaning “cell movement”) occurs, and the two new cells move apart.

This cycle continues until the skin cells receive specific chemical signals telling them to cease dividing. At this point, the wound is completely covered with new skin and the scab, having served its purpose, falls off.

Proteins and Carbohydrates

Carbohydrates and proteins are crucial to all forms of life. They have many functions within the body, and sometimes work together in order to complete certain tasks.

Carbohydrates are made of carbon, oxygen & hydrogen molecules. Because of the carbon backbone, they are a type of organic chemical. Many people cut carbohydrates out of their diet when trying to lose weight because loading up on carbohydrates leads to increased deposits of fat. However, avoiding all carbohydrates is very dangerous, as they are a major source of fuel for metabolism, meaning that you literally couldn’t live without them.

Glucose is the most commonly known carbohydrate. It is a simple sugar (or monosaccharide) used for metabolism and cell respiration in practically all known organisms. It is often called “blood sugar” and is made available for cell absorption via the hormone insulin (a type of protein). Inside of the cell, mitochondria convert the glucose into ATP, which the cell then uses and stores as energy.

Proteins are just as important, as they are the primary building blocks of your body, creating nails, muscles, skin, joints, and other tissues. They also act as hormones, molecule transporters, metabolic reaction accelerators, and play a crucial part in your immune system.

When we consume proteins, they are broken down into amino acids which are then used to build new proteins with specific uses and functions. Ribosomes inside of cells form the amino acids into polymers called polypeptides. With the help of specific proteins these polypeptides are then folded into proteins. The way the polypeptides are folded and/or combined determines what type of protein they will become, and what function they will serve within the organism.

Proteins and carbohydrates each have their own individual purposes within our bodies, but very often the two must work together in order to assist us in our day-to-day lives, which would not be possible without either of them.