Lesson 1: Mutation

Hi,

On Nov 10, I happened to chance upon something in the Straits Times that I wanted to talk to you about.

There was a photograph of a cute baby, all of 2 weeks, born in China who has 8 toes on each foot!His hands looked normal with 5 fingers each.

This is the result of a mutation. His parents are normal, with 5 digits in each limb.

Mutations are caused by mutagens or carcinogens found in the environment, radiation from the sky (e.g. cosmic rays, X-rays, gamma rays, even UV light), natural radioactivity from minerals within the Earth, and a multitude of chemicals. Gamma rays are used nowadays to irradiate grains and seeds before storage to kill all fungi and bacteria on the surface of these seeds.

A mutation occurs when one or more genes (on the DNA) get changed during meiosis. The resulting gamete if fertilized, will develop into an offspring which may show such effects as polydactyly (too many fingers or toes). But many will have no visible effect.

Most of us have tiny changes in us which are called genetic variations. These are mostly not visible and inconsequential and if the changes are not deleterious, we go through life not knowing that we are different, physically and physiologically, that is.

Normal alimentary canal
(Source: www.scienceaid.co.uk)

I have read about people who are middle-aged before they found out that they have 4 kidneys and 4 ureters. It was only discovered when they had a radioactive dye injected into them to trace the path of discharge of urine from the kidneys via the urinary bladder.

Another incident involved a person who did not know that he had laterally-inverted visceral organs. This means that his internal organs were on opposite sides from nearly all people. His stomach was on his right, the appendix on his left, etc...

Oh, I forgot about his heart being tilted to his right instead of his left...

Students, please remember what I told you about the diagrams in text books? They are always drawn laterally inverted. You have to imagine that you are a doctor looking
at a patient lying on a operating table. The textbook diagrams always show organs as viewed by a doctor.

Cheers,
Have a good day.