Answers to Student Questions

Unit 2 Genetics

1. What's the relationship between genes and proteins?

A very good question! Let's see if we can figure out the difference. J. Martha

Genes and Proteins

The short answer to this question is, genes provide the information for the construction of proteins. Proteins are very important molecules in our body, because they serve so many important functions. The proteins that are constructed by your cells have several functions:

• Structural functions, such as helping to maintain cell shape.
• Enzyme functions, such as catalyzing chemical reactions.
• Signaling functions, such as serving as chemical messengers in the immune system.
• Hormone functions, such as carrying chemical messages throughout the body via the bloodstream.

Where do proteins come from? Proteins are made by cells by combining amino acids. Amino acids are obtained in two ways - your body synthesizes some, but many come from the food that you eat.

How do your cells know how to make the hundreds of different of proteins that your body requires? That's where genes come in. Genes are the bits of information that are found in the DNA, the genetic material that is found in the nucleus of every cell in your body. Cells access the information, or the "code" found in the genes that instructs the cell which amino acids to put together, and in what order, to make a protein. It is interesting to note that it is small variations in the genetic code from person to person that allows for varying amounts and types of protein construction from person to person. This is what accounts for some of our individual differences!

2. What is the difference chromatin, chromosomes and sister chromatids?

Hmmm... as a biology teacher, I understand those terms can be confusing. I will try to clarify them for you. J. Martha

Chromatin, Chromosomes and Chromatids

The reason these three terms, chromatin, chromosomes and chromatids, are easily confused is due to the fact that they are all different forms of the same thing - DNA. Deoxyribonucleic acid (DNA) is the molecule that is found in the nucleus of our cells, and holds the genetic instructions for the structure and function of all living things. The DNA that is pictured to the right in an artist's drawing of its famous double-helix structure. The structure of DNA is usually modelled or drawn in textbooks, because the actual DNA molecule detail is far too small to be seen with the light microscope. When you look at a cell under under the light microscope, you are far more likely to see DNA as part of much larger structures - which brings us back to the terms we are trying to understand: chromatin, chromosomes and chromatids.

With a powerful light microscope, the nucleus of a cell can be seen. If the cell has been stained, chromatin is usually fairly easy to see (the name chromatin literally means "coloured material"). Chromatin is simply a gathering of the DNA of the cell, in a large clump mixed together with some proteins. Imagine a strand of DNA as a single elastic band that you hold twisted between your thumbs - by itself, it is easy to see the structure of the elastic. Now imagine a huge tangled ball of elastic bands, the kind you might find in a junk drawer at home. The tangled ball represents the chromatin in the nucleus. Because DNA is a small and delicate molecule, it is almost always found in the form of chromatin - bunched together and mixed with proteins. Biologists believe DNA exists mainly in the form of chromatin because it is more protected in a large "clump".

There are times however, when the clump of chromatin "unwinds". This happens during cell division; it is necessary to make a copy of the DNA, so each daughter cell gets a complete copy of all the genetic instructions contained in the DNA. When chromatin "unwinds" we can finally see more defined versions of the DNA molecule - chromosomes and chromatids.

A chromosome is a actually one very long strand of DNA. Under the light microscope they can only be seen during cell division - this is when the individual chromosomes have doubled in preparation for cell division. When the chromosomes have doubled, many of them appear to have an "X" shape, as shown in the diagram to the right. The two segments that make up the chromosome are known as chromatids, and represent identical copies of the same DNA strand.

You can also see in the diagram that the two chromatids that make up the chromosome are held together by a structure called a centromere. During cell division, the chromatids will separate at the location of the centromere forming two separate strands, each of which goes to opposite poles of the dividing cell. As the cell division continues, the two strands will become permanently separated, one each in the two new daughter cells formed by the cell division.

Now here's the real confusing part! Once the two chromatids have separated and have migrated to their respective daughter cells, they are now known as chromosomes! The term chromatid is only used when a chromosome is in a "doubled" state (as shown in the diagram to the right), to help differentiate between the two different strands.

There! Hopefully that has cleared up some confusion between three similar genetic terms.

3. Are genes and DNA the same thing?

In a way "yes", and in another way "no"! Let me explain the difference. J. Martha

Please take a quick look at the image of DNA in the answer to the previous question - the famous double-helix of the DNA molecule is unmistakeable. But what is the purpose of this fascinating molecule? The ultimate purpose of DNA is hold the information that allows living things to develop and function. The complexity of living things requires many thousands of pieces of information, all of which must be stored by the DNA. This is where genes enter the picture.

Genes are segments of the DNA molecule that serve as units of heredity. Each gene carries a bit of information that helps direct the development of the organism. For example, a particular gene may carry information for hair colour, when expressed in the organism, results in red hair. A different version of the same gene with slightly different information may result in brown hair in the organsim.

So to answer the question, genes and DNA are really not the same thing, but genes ARE specific segments of the DNA molecule. In a particular chromosome (see question #2 above) there are large parts of the DNA molecule that are not genes - these parts of the DNA may be responsible for activating and deactivating genes, or they may be responsible for nothing at all.

Unit 3 Chemistry

1. Hi... I'm a little confused about something. Are the ions on the Data Booklet also  molecular compounds? Some of them are two non-metals joined and a molecular or covalently bonded compound is a compound that contains only non-metals.

Hi Nancy, besides being the author of the chemistry unit, I am a teacher at Stelly's Secondary School in Saanich, which is a couple of (metric) stone throws away from Buchart's Gardens. D. Lacy

Molecules, Compounds, and Polyatomic Ions

I'd like to start off with these ideas:

• A molecule is a group of atoms connected to each other with covalent bonds and which have a fixed number of atoms. For example, CH4 is a molecular compound that contains 5 atoms covalently bonded. DNA similarly is a molecule with billions of atoms, but still with a definite number. Glass, on the other hand contains covalent bonds but is not a molecule because it is an array of atoms that extends indefinitely. (It is a network solid).
• A compound is by definition electrically neutral. Physically, it is something that can be put into a jar. You can get a jar full of sodium chloride, but you can't get a jar full of just sodium ions, or just chloride ions. So no individual ion is considered a compound.

The polyatomic ions in the data booklet are definitely connected by covalent bonds. It would be correct to call them molecular ions, but this usage is not particularly common. They are definitely not compounds when taken individually, such as NH₄⁺¹ or  NO₃^-1 . When both ions are taken together they still are not molecular compounds, since they are formed from ions they are ionic compounds.

This means that compounds made of polyatomic ions have the interesting feature that they contain both ionic and covalent bonds.

 "A molecular or covalently bonded compound is a compound that contains only non-metals."

Here's a nit-picky distinction that I rarely share with my students: Compounds of non-metals have covalent bonds. However, there sometimes metals engage in covalent bonds too. The data table shows three of these: chromate and dichromate, which have a chromium oxygen covalent bond, and Hg₂⁺² which contains a mercury-mercury covalent bond. So although I don't go into the explanation with my students, I am careful about how I phrase these things.

Well, I hope I have covered off the right points without raising any new problems or too much overkill! But feel free to write back until it is all sorted out.

2. I wanted to know if you could explain what exactly are the purposes for an electron orbit and how it affects the atom?

Hi Naila, good question - thank you. Here's an answer for you. D. Lacy

We have to be careful about how we use the word 'orbit' when talking about the atom. When the word orbit is used on the provincial exam, it is better to think of it as meaning energy level. That is, a region of space surrounding a nucleus, in which the electrons have a certain amount of energy. The lowest energy level can have two electrons and the next one up can hold eight. The electrons don't fly around the nucleus like a fast moving particle. They just exist in all parts of the energy level all at once.

Counting the number of electrons in the energy levels tells us about how the atom can react. For example, oxygen has 6 electrons in its second energy level. It can hold two more electrons in this orbital, which tells us that oxygen is likely to form an ion with a minus two charge. Neon, which has 8 electrons in a full orbital is not expected to form an ion at all.

I would stay away from the term orbit. How did 'orbit' come into use? The Earth and other planets orbit the sun, which means of course that they move in a path around the sun. The planets are always in one particular place at any given time, but always on the move. An early model of the atom by the great physicist Neils Bohr treated electrons like a planet going around the Sun, but experiments showed it wasn't a very good model and he quickly abandoned it. He then came up with a much better model that is still in use today. Unfortunately the image of electrons whizzing around the nucleus keeps getting used even though it is wrong.

As you learn more about the atom in later courses, the model gets more sophisticated. Eventually is can explain a lot, such as why ruby crystals can produce laser light and why diamond is the hardest substance known. These come from a theory of matter called quantum mechanics, and Einstein and Niels Bohr were early thinkers on the matter. It is one of the two most successful theories in all of science.

But it does have some strange results. For example, consider that I am writing this note at the keyboard of my computer. The theory says that an electron in the lowest orbit, or energy level, of an atom in my finger exists all around the atom all at once. The amount of negativeness from the electron gets less and less as the distance from the nucleus increases. But - and this is a little strange, but as far as we know it is true - the negativeness never goes to zero. A tiny bit of it is in the wall next to my computer, even less of it is on Mars, and much less, but still some, is in the Andromeda Galaxy, 4 million light years away! How's that for the idea that everything is connected to everything else?!

Unit 4 Electricity and Magnetism

1. How do you describe and diagram magnetic field lines?

Considering the confusion with "magnetic north" and "geographic north" of the Earth, this can be tough to understand. But let's see if we can sort it out. J. Martha

Magnetic Field Lines

The first part of the answer is relatively simple. When you are diagramming and describing magnetic field lines, you always diagram them as running from the N-pole toward the S-pole of the magnet. So if you were diagramming the field lines of a simple bar magnet, it would look like this (note the direction of the arrows from N to S):

Another situation is when a wire has an electric current going though it. In this case, the magnetic field goes around the wire in a circular pattern. To determine the direction of the magnetic field you use the left hand rule.  Point your left hand thumb in the direction of the current and the way your fingers grab the wire is the direction of the field. This can be seen if you check out this page (be patient while it loads - it is a QuickTime movie).

If you are dealing with the Earth, this can be a bit confusing! Since the N-poles of magnets point to the Earth's "north" - there must be a magnetic south pole there. How did this situation occur - is it a mistake of science? Well, not really.

In the late 1500's William Gilbert studied natural magnets by floating them and suspending them on strings. He noted that they would always align themselves in a North-to-South orientation. Because of this orientation, Gilbert decided to describe the ends of the magnet according the geographic poles they pointed to. Gilbert labeled the end of the magnet that pointed to geographic North the "North-seeking pole" - the other end of the magnet was labeled "South-seeking pole".

Over time, the "North-seeking pole" of magnets has been shortened to "N-pole", or "N". Likewise for the "S-pole"or "S" end of magnets. Of course, N-poles are attracted to S-poles of magnets.  Therefore, if the N-poles of magnets are attracted to the geographic North of the Earth, according to Gilbert's system, which we still use today, the magnetic pole near Earth's geographic North must be an S-pole.

This may seem a little confusing, but what one must realize is that the magnetic poles really have no physical or scientific connection to the geographic poles of the Earth. While geographic North and South never move and will always be on the same place on a map, the magnetic poles actually move year to year.  Geologic evidence suggests that the poles actually "flip", on average once every 200 000 years. In fact, we are long overdue for a flip of the Earth's magnetic poles!

So the fact that there is an S-pole near the geographic North pole is simply a result of a centuries-old naming method for the poles of magnets that we still use today.

2. What is the difference between current and voltage? When you turn off a radio, have the electrons disappeared or not? Why? When objects are neutral and have a similar amount of protons and electrons, do they still repel and attract to one another?

Thanks for your email and your excellent questions. I'm the author of the Electricity unit for Science Foundations - hopefully I can help with your questions. J. Martha

Voltage and Current

The unit for current is amperes (often called "amps"), and the unit for voltage is volts. Voltage is a measure of how much energy electrons have, and current is how many electrons pass a point in a circuit every second.

It might help to think about the flow of water when trying to understand the difference between voltage and current. Imagine two waterfalls – one short, one very tall but otherwise similar in all respects. The water falling from the taller waterfall would reach a greater speed before hitting the river below, striking with a terrific splash. The water falling from the short waterfall would splash too, but with a much lower speed and not nearly as spectacular. The taller waterfall represents high voltage, the short waterfall represents low voltage. The higher the voltage, the more energy each electron has. Voltage is what makes electrons "flow" in a circuit, much like the difference in elevation of a waterfall makes water flow.

Current can also be visualized with water. Imagine two waterfalls of the same height, but one very wide and deep – the other narrow and shallow. The deep wide waterfall would have much more water flowing over it than the trickle of water coming over the narrow and shallow waterfall. More water passing a point every second means a greater current – and it's the same with electricity. More current means more electrons flowing past a point per unit of time.

Moving Electrons

Electrons don't disappear when you turn off a radio, but they do stop moving. With the radio turned off, there is no voltage applied to the circuit. Without voltage, there is no difference in energy to make the electrons move – so they don't. As soon as you turn on the radio, the voltage returns and the electrons start moving again, creating an electric current.

Neutral Objects

Two neutral objects will not attract or repel, because there is no net difference in charge. Protons are positive, and electrons are negative – so when they are in relatively equal amounts and spread out amongst each other, there is no area of net positive or negative charge.

Now, if I were to bring a negatively charged rod close to a neutral doorknob that would create a repulsion between the electrons in the rod and in the knob, making the electrons in the knob move away. This would create areas of net positive and negative charge in the knob, which could in turn result attractive and repulsive forces on other charged objects brought nearby.

I hope these answers have been of help to you – please don't hesitate to ask other questions if you need to.

Unit 6 Earth Forces

1. Where exactly is the Mid-Atlantic Ridge?

2. How do we know the locations of all the trenches and ridge in the world?

Hi Katie: Thank you for your questions. Lets tackle them in order. J. Milross

Trenches and Ridges

One thing to keep in mind. The Mid-Atlantic Ridge is not a perfect crack in the oceanic crust, but rather a series of little cracks that are joined together. The pattern is similar to a zig-zagging  zipper. [I hope that makes sense to you]

We know the locations of trenches and ridges because geophysicists and oceanographers have studied the bottom of the oceans using sonar (sending sound waves to the ocean floor, and studying the "echo", just like ultrasound used to "see" babies inside their mother's womb), seismic waves (caused by earthquakes), and x-rays to observe the oceanic crust as if  there were no water in the way. Trenches occur where two plates are colliding (oceanic - oceanic, or oceanic - continental), and ridges form when two plates  are moving away from each other (in the ocean, these are called ridges; on land, they are called rifts). By studying the movement of the plates, scientists could anticipate where they should expect plates to be coming together, or moving apart.

Thanks again for your great questions, and for using our book. If you should have any other questions, please don't hesitate to contact us. Remember: Earthscience Rocks!

3. What are the benefits of living near active volcanoes?

Hi Ashley: Thank you for your question. At first glance, living next to a volcano doesn't seem like a good idea. Personally, the thought of front row seats to a violent eruption sounds a little too extreme for this science teacher. J. Milross

I suggest there are two main benefits to living next to a volcano:

1. Volcanoes occur in areas where there is magma  (molten rock) under the ground (that's why volcanoes happen - the magma makes it to the surface). The magma is very hot, and heats up large areas surrounding it. Water trapped in rock underground gets heated by the magma, and can come to the surface as a geyser, or a hot spring. These features can be used to generate hydrothermal power, or be used for hot water, or the heating of homes. Harrison Hot Springs uses hydrothermal springs (heated by magma) to attract tourists.

2. When volcanoes erupt, they send a great deal of ash into the air, which covers large areas of land. This ash is rich in nutrients (nitrogen, potassium, etc), which makes for ideal fertile soil.  Trouble is, you're farming next to a volcano...

I hope this helps. If you have any other questions, please do not hesitate to ask. Thank you again for your thoughtful question, and thank you for using Foundations 10. Best of luck.

4. How does the presence of glaciation in places like India add credibility to Wegener's theory?

5. What does looking at the Earth's surface tell a geologist about what is happening underground?

6. What are two different uses for a geological map of an area?

Here is a response from our Earth Science author, J. Milross.

The Earth's Surface

4. India sits across the equator, and is currently considered tropical in many areas. Even low elevation areas show evidence of large ice sheets having once covered most of India. This evidence, (glacial scratching, deposits, and u-shaped valleys), does not make sense for such a warm area. The pattern of the glacial evidence also does not make sense for India in its present position. It does make sense, however, if India is part of Pangaea, and is moved to its position 200 million years ago, much further south, towards the pole.

5. Geologists will look for evidence on the surface that reveals what is going on underneath. For example, a steep, flat-sided cliff may suggest a deep fault. A small area of rock that stands out from the rock around it may indicate igneous rock that cooled underground, solidified, then had the rock layers above it removed (through erosion). A hilly area may indicate the presence of magma deep underground causing the surface to buckle. Rounded hills may indicate tectonic forces being applied.

6. Searching for: mineral resources; sources of water; areas that are safe to build houses, buildings, or highways; areas that are suitable for farming; areas that may be subject to earthquakes; etc.

7. I was just wondering, what's the answer to - "How do geologists determine the start and end of an era?" 

Hi Lilian: Thanks for your question. I hope this helps:

Eras

On page 234 of the text, the third paragraph describes the divisions of the geological time scale being determined by things like rock types, fossils, etc. The eras are usually divided by the first appearance, or the last appearance of a group of organisms. For example, the beginning of the Cambrian period was marked by the "Cambrian Explosion", a time when there was an incredible amount of diverse (really strange and different) life forms first appearing on Earth.

Thank you again for using Foundations 10. Good luck on your final. Sincerely, J. Milross

8. What does the magnetic pattern in the bands of rock suggest about the formation of the sea floor?

9. Why are the magnetized particles in igneous rocks on the sea floor are not all pointing in the same direction?

Magnetism and the Sea Floor

Hello, and thanks for your question. We asked our Earth Science author and here is his reply. Good luck on your upcoming exam.