What’s the Difference Between a Gene and a Chromosome?

All life is made up of cells. All cells in the human body, except red blood cells, contain chromosomes. Chromosome comes from the Greek word khroma meaning “color” and soma meaning “body”. Chromosomes got their name from the first lab experiments in the 1880s where it was revealed that chromosomes could be stained with dyes, making them easier to study.

A gene is located on a chromosome. Every factor in inheritance is due to a particular gene. Genes specify the structure of particular proteins that make up each cell. Gene comes from the Greek word genea meaning “generation,” “origin,” “beginning” or “kin.” The word “gene” was shortened from “pangene” which means “all-generation.” Genes contain DNA, the chemical basis of heredity.

Think of it this way: DNA is in genes, genes are on chromosomes.

When it was first seriously conceived to ‘map’ all genes on all human chromosomes, it was called the Human Genome Project—a combination of “gene” and “chromosome.”

 

What happens when a chromosome is abnormal?

Each chromosome has a specific and proper structure and color. Together, all the chromosomes in our body form a distinct pattern called the human karyotype. We have 46 chromosomes (23 from each parent), however there are variations in reproduction due to abnormalities in the karyotype of an individual. A few of these abnormalities are beneficial, most are harmless, and a few are catastrophic. A major chromosome abnormality (MCA) accounts for half of all spontaneous human abortions. An MCA occurs in about 1 in every 100–200 births. Recent medical diagnostic techniques can now detect many MCAs long before the child is born by analyzing the patient’s blood under a microscope. MCAs take one of five forms:

  1. In duplication, instead of the normal two, the individual has three copies of the chromosome in every cell of their body (trisomic). Most trisomics result in a spontaneous abortion—but not always. Trisomy-21 (Down’s syndrome) occurs 1.5 times in every 1000 births—the individual has three copies of chromosome 21. Trisomy-8 (Edward’s syndrome) occurs 3 times in every 10,000 births—the individual has three copies of chromosome 18. Trisomy-13 (Patau’s syndrome) occurs 2 times in every 10,000 births—the individual has three copies of chromosome.
  2. In deletion, a piece of chromosome may go missing. The missing piece is usually from the end of the chromosome, but can be missing from the middle as well. The types of symptoms and their severity will vary depending on the size and location of the deletion. Deletion syndromes occur at a frequency of about 1 in every 16,000 births. In Wolf-Hirschhorn syndrome (1 in every 50,000 births) the abnormality occurs on chromosome. In Cri du Chat syndrome (1 in every 50,000 births), the abnormality occurs on chromosome.
  3. In translocation, a whole or a piece of a chromosome becomes attached to another.
  4. In inversion, a portion of the chromosome breaks off, turns upside down, and reattaches.
  5. In rings, a portion of the chromosome breaks off and forms a circle, with or without loss of genetic information.

In the last three forms, there is an alteration in the pattern of genetic information.

How is Race Defined?

A way of thinking about “race” is to define it as including all members of any human group that can successfully breed with each other. A “race” includes all the descendants of a common human ancestor. So it is like a family, a tribe, an ethnic group, a nation, or the entire world’s human population. This is the broadest biologically defensible definition.

Otherwise, “race” is a social construct rather than a biological one. It is impossible to scientifically define as distinct a human race as apart from another distinct human race on biological criteria alone. There are as many human races as there are human beings due to the genetic uniqueness of each of us. The only possible exception to this would be identical twins, where the number of members of that race would be exactly two!

There are genetic-based outcomes among populations living in specific geographical areas that can set them off from populations in other geographical areas. These outcomes may make certain populations more or less susceptible to having specific anatomical features or health conditions. There may be a survival advantage favoring a particular feature in a certain environment. For instance, more prominent eyelid folds among the Inupiak people of the Arctic may help protect them against snow blindness. Such an anatomical feature would be of no advantage in a snow-free environment.

Tay-Sachs disease, a genetic-based disease causing mental and physical deterioration and often death by age 4, is more prominent among Eastern European Jews. Sickle cell anemia, a disease affecting red blood cells that results in early death (often by age 40), is more prominent among sub- Saharan Africans.

The rate of giving birth to twins varies with geography. West Africa has the highest birth rate of twins in the world. For example, the Igbo-Ora of Nigeria have 31.6 twin births per 200 live births compared to an average of 1 twin birth per 200 live births in European nations.

The fact that all anatomical features or health conditions differ among human populations proves only that there is variation everywhere on Earth. But to define any one population as a “race” as apart from another population as another ‘race’ is to divide people on a crude and misleading basis. Such a judgment invites bias and prejudice.

“Race” has been given great prominence in Western history, particularly over the last 600 years with the advent of New World exploration, the contact of Europeans with non-Europeans, and European empire building. “Race” has often been the ill-conceived basis for the most terrible discriminatory policies, laws, social movements, ethnic cleansings and wars in the long and sorry history of man’s inhumanity to man. “Race” is today a scientifically and socially bankrupt concept.

There is a 1 in 200 chance that a male human worldwide is a direct patrilineal descendant of Genghis Khan.

The man with the oldest known individual ancestor is British professor Adrian Targett. DNA tests matched Professor Targett’s with that of a 9000-year-old skeleton found in Cheddar, England.

The oldest authenticated pair of female twins was Kim Narita and Gin Kanie of Japan. They were born on 1 August 1892. Kim died of heart failure in January 2000 at 107 years of age.

The longest living triplets were Faith, Hope and Charity, who were born in Elm Mott, Texas, on 18 May 1899. Faith was the first to die at age 95 in October 1994.

The world’s oldest quadruplets were the Ottman siblings—Adolf, Anne- Marie, Emma and Elisabeth. They were born on 5 May 1912. Adolf died first at age 79 in March 1992.

Why Does Natural Selection Take So Long?

Although there is fierce debate about how fast natural selection can proceed and if natural selection is still proceeding in humans due to our technology, there is a short answer: Speed is probably not very important in natural selection and certainly it is not the only consideration.

There is a danger in mutation. Most mutations do not help the species survive. A species and an environment exist in balance with each other. Populations simply adapt to their current surroundings and the changes to them; they do not necessarily become better in any absolute sense over time. A change in the environment may require a change in the species in order for it to survive. But if a mutation spreads too quickly across an entire species it may prove maladaptive to the species if the environment undergoes a further change.

More diversity in mutations and hence change is probably better than speed in a mutation becoming widespread in a species.

There is also the possibility that a trait that is successful at one time may be unsuccessful at another. This principle was demonstrated by the classic experiments by Drs. C. Paquin and J. Adams. They developed a yeast culture and maintained it for many generations. Every so often, a mutation would appear that allowed its bearer to reproduce better than its contemporaries. These mutant strains would crowd out the formerly dominant strains. Samples of the most successful strains from the culture were taken at various times.

In later competition experiments, each strain would outcompete the immediate previous dominant type in a culture. But interestingly, some earlier strains could outcompete strains that arose later in the experiment. Competitive ability of a strain was always better than its previous type. Yet competitiveness in a general sense was not increasing. The success of any organism depends on the traits of its contemporaries. There is likely no optimal design or strategy for most traits, only ones based on chance such as the competition and the environment.

How Can Human Beings Be “Enhanced”?

There are currently five general areas of experimental therapies that hold the prospect for “human enhancement”:

  • DNA. We may one day gain the power to insert new genes safely into various parts of the adult body and perhaps someday also into gametes and embryos. According to Moore’s law, the performance of computing doubles by any measure you use every 18 months. This has been the case for the last 40 years resulting in computer power increasing more than 100 million times over that period. This is why your microwave oven today has more computer power than all the computer power existing in the world 50 years ago. DNA research developments occur very rapidly now. The rate of change is increasing dramatically too. It took 15 years to sequence the genome of HIV. The SARS genome was sequenced in 31 days.
  • Drugs. We may one day gain the power to enhance physical performance using drugs such as safe steroids.
  • Cognition. We may one day gain the power to alter safely cognition, including memory, mood, appetite, libido and attention, through psychoactive drugs. There are currently over 40 cognition-boosting drugs in development designed to improve wakefulness, memory, decision making, planning and other aspects of thinking. One of these drugs is modafinil. Modafinil is a “wakefulness promoter” that was originally developed to help people suffering from narcolepsy and other sleep disorders. It was discovered that for those who have normal cognition, modafinil improves not only planning but also decision making, verbal memory and visual memory.
  • Implants. We may one day have the power to replace body parts with natural organs, mechanical organs, or tissues derived from stem cells, perhaps soon we will be able to rewire ourselves using computer chips implanted into the body and the brain.
  • Life extension. We may one day have the power to prolong not just the average, but also the maximum human life expectancy. Some scientists predict that in 20 to 30 years, it will be possible to deliver radical increases in longevity largely by repairing cellular and molecular damage. Not surprisingly, not all scientists agree.

How Old is My Body if My Cells Keep Renewing Themselves?

About a century ago, scientists first discovered that most of our brain cells formed during fetal development stay with us throughout life. But this discovery stimulated other scientists to study the age of cells throughout the human body. If we look at the adult human body from head to toe at age 40, the list goes something like this:

  • Brain cells of the cerebral cortex (the grey matter) are with you from birth.
  • Brain cells of the visual cortex (the array of cells in the front of the brain used for vision) are with you from birth.
  • Brain cells of the cerebellum (the structures at the base of the brain) are slightly younger than you are.
  • Intercostal muscle cells are about 15.1 years old.
  • Gut lining cells are about 5 days old.
  • Gut cells other than the lining are about 15.9 years old.
  • Skin cells are about 14 days old.
  • Red blood cells are about 120 days old.
  • Bone cells are about 10 years old.

We don’t know precisely the average ages of eye-lens cells, heart cells, liver cells, pancreas cells, fat cells and bone marrow cells.

Will Robots Ever Become Just Like Human Beings?

We are getting very close to building an almost human-like robot, however, there will never be a completely human-like robot since robots will never be able to biologically reproduce. Other than this, theoretically, robots could look, act, think and feel like humans in every way. The technical problems that need to be overcome in achieving this are being addressed one by one.

The development of humanoid robots today focuses on three major areas:

  1. Control of manipulators (what it can do);
  2. Biped locomotion (how it can walk); and
  3. Interaction with humans.

The movements of robots have previously been awkward and non-human like. In 2006, the “Flexible Spine Belly-Dancing Humanoid“, a robot that can belly dance just as well as a human, was brought to life.

Today, humanoid robots are so well-developed that they are being regarded as human beings by 10-month-old infants in laboratory experiments.

People find robots more likeable the more human they look, but only up to a point – once they become too lifelike they become frightening. The human-sized, humanoid robot “H7,” invented by a team of researchers led by Dr. K. Nishiwaki is designed for autonomous walking, performing tasks and interacting with humans in an indoor environment.

Can an Extinct Human Like the Neanderthal Man Be Cloned and Brought Back to Life?

Theoretically, this is certainly possible, but there would be technical problems along the way in trying to do it. There are also many ethical and moral issues to be resolved satisfactorily beforehand.

After all of this, the steps for cloning a Neanderthal would be the following:

  1. Obtain a reliable DNA sample. A thorough search is required for cells from the to-be-cloned Neanderthal, including bone and teeth cells. Neanderthal hair and skin cells could be used if available, but since hair and skin make poor fossils compared with bones and teeth, none survive for the Neanderthal. Extracting healthy DNA fragments from the nucleus of cells of Neanderthal bones and teeth would be very difficult to do.
  2. Rebuild the genome. The broken DNA of the Neanderthal is reassembled using the genome of a related living human as a guide.
  3. Swapping DNA. Eggs from the ovaries of a living human are removed and their nuclei replaced with the restored genetic material from the Neanderthal.
  4. Stimulating the eggs. Genetically engineered restructured eggs are treated with chemicals or perhaps electric current to fuse the nuclei with the eggs and trigger cell division.
  5. Implanting the embryo. After the desired cell division has started and progressed to form an embryo of about 200 cells, the embryo is implanted into the womb of a living woman where it is carried to full term like any other human embryo.
  6. Birth. The surrogate mother gives birth to the Neanderthal baby in a normal human birth, and the baby will grow up into a Neanderthal adult.