Genetics Extension Questions

This is optional extension work on Genetics for when you have finished the Punnet Squares worksheets.

1. Each human body cell (as opposed to gametes) has 23 pairs of homologous chromosomes. One chromosome from each cell is placed in each gamete (sperm or egg), so each one has a random set of 23 chromosomes. When a sperm and an egg combine to form a zygote, the zygote has a full set of (46) chromosomes, so it can grow into a baby.

A. How many different gametes can one person produce?

B. How many different children could one couple produce (if they were fertile for long enough)?

Note: During meiosis, individual genes are exchanged between chromosomes before they separate into different gametes. This results (crossing over) in an even greater (almost infinite) number of possible offspring. Hair colour and eye colour are located on the same chromosome, so that’s why most people who have blonde hair have blue eyes and vice versa, however occasionally this crossing over results in people who have blue eyes and dark hair (or dark eyes and fair hair).

Hints
Spider mites have different numbers of chromosomes, (from 4 to 14) however let’s imagine a particular spider mite (male and female) has 4 chromosomes in total. Each pair of chromosomes is shown as a different colour. Clearly four different gametes are possible, so sixteen different offpsring are possible.
Use the information above to explain why it’s unlikely that couples have two children the same (except identical twins). Suggest a reason crossing over might occur, given that it appears unnecessary for the purpose of ensuring variation among offspring.

As another exercise, determine the phenotype ratio of two herterozygous parents for two traits, for example two parents who are right-handed (and carry the gene for left handedness), and have black hair (and carry the gene for blonde hair) have many children. Determine the ratio of
black+right : black+left : blonde+right : blonde+left.

7B: Anaglyphs

In class we will make anaglyphs, and look at them using the filters. Here is my example. Remember that the red filter should be on the left.

Of course feel free to search around online, but I think the best directions are here.

We will (later) make 3D Stereograms (“Magic Eyes”). Use this site to make your image and this site to make it into a stereogram. Can you read the (rather unimaginative) text in this test of mine.

Test date: Wednesday 13th June

You should be able to:
1. Define and explain the words transparent, translucent and opaque, and give an example of something which is each of these, and explain why it is useful.
2. Show how light reflects off a mirror, and describe the relationship between the angles of incidence and reflection, and label these angles on a ray diagram.
3. Draw ray diagrams to show why an image is seen in a plane (flat) mirror.
4. Draw your name as it would be reflected in a mirror.
5. State the primary (additive) colours (red, blue and green).
6. Describe what colour differently coloured objects will appear when they have different colours of light (and white light) shone at them and are looked at through different filters.
7. Draw labelled ray diagrams to show what happens to a light ray as it is refracted through a rectangular block (of glass, perspex etc).
8. Draw a ray diagram to show why a rod looks bent in water.
9. Draw a ray diagram to show what happens to white light as it is refracted through a prism and separated into a spectrum.

7B Homework: Circuits Simulation

Go to this website and click on “Run now” button and run the program (you may need to tell your computer to ‘trust’, ‘keep’ the file or whatever.

1. Make a circuit consisting of two or three batteries, two lightbulbs and two ammeters like we did in class today. The ammeters should be in different places (there should be at least one lightbulb between them). Please use the normal ammeters and not the “non-contact ammeters”. You need to select ammeters on the right of the screen, as shown in the image below.

Of course please feel free to experiment around with different components.

7B Work for Tuesday 8th May

Watch BrainPop “Electricity and Electric Circuits”.

Take the printed quiz on Electric Circuits (on my desk in M301).

Students should then work from textbooks Physics 11-14, which can be found behind the whiteboard close to the door to M301.

If students finish the above, they may continue with the work from Friday (which is homework due on Wednesday).

7 Science Homework: Electricity Models

Homework to finish by Wednesday (9th May):

Grade 7 Science Homework: Models of Electricity

Today we looked at three models for how electrons carry energy around in a circuit. Answer the following questions (the last one is optional).

The exam will be at 9:10 on Friday April 27th. It will only cover the current topic: “The Earth and Its Chemistry” (starting from the astronomy we covered). It will not cover the unit on food.

Resources:

• Spotlight science
• Brainpops – solar system, the rock cycle, compounds and mixtures
• Class notes pages
• Your assignments on planets, building design, mining and elements

Strategies:

• Use the work you have done carefully – this should be the most useful thing
• Use the study questions to organise a summary. Don’t just answer the question, put down as much as you can about each topic heading.
• Use as many drawings and diagrams in your study as you can.
• Pick out key words for each topic
• Identify which sections of the work you have found difficult.
• Check your information with a friend.
• Don’t do all your review in one go. It is better to do several shorter review sessions than one long one.
You should be able to:
• state, for planets, moons and the sun, which orbit which.
• recall the order of the planets starting from the sun
• explain the main trend (pattern) for the temperature of planets in the Solar System.
(Note: you do NOT need to memorise the temperatures of the planets)
• label and describe the four main layers of the Earth.
• Give examples of how we use at least three different elements
• explain why some crystals (in rocks) are larger than others.
• outline why earthquakes occur and how this relates to the structure of the earth
• explain, from our experiment, which shaped buildings are more likely to survive an earthquake, and explain at least one technique engineers use to make buildings more earthquake-resistant.
• explain how to use filtration, dissolving, evaporation, distillation and magnetic separation to separate. components of different mixtures.
• identify appropriate separation techniques for different mixtures
• identify physical and chemical properties.
• explain the difference between elements, compounds and mixtures, and identify and give examples of each.
• explain the difference between chemical and physical change.
• describe different types of evidence for chemical change
• identify reactants and products in chemical reactions
• write a word equation for the rusting of iron.
• explain the chemical reaction which occurred when: a. a match coated with iron oxide is burned b. copper carbonate is heated over a bunsen burner
• explain how electricity can be used to separate compounds.
(Note: we will cover this next week when we will use a process called ‘electrolysis’ to separate components of a solution.)
Please email me if you have any questions or concerns.

7B Homework

This homework is for Wednesday 15th February.

Due to after school commitmentes, I am only putting this on my blog at 7:30, which may be too late for some students to see it and/or do the homework, therefore this will not be due until the next class next Tuesday (21st). The poster comparing sizes of planets and the report on the blocks experiment should both have been handed in, unless we made arrangements otherwise.

The Problem

While preparing for a science experiment I accidentally dropped a tray carrying a glass jar of sugar and a glass jar of salt, so I now have glass, sugar and salt all mixed up (as a mixture). I also have some ethanol (pure alcohol). Sugar dissolves in ethanol but salt doesn’t, and of course both sugar and salt dissolve in water. Ethanol most not be heated over a flame because it can catch on fire, however since its boiling point is 78°C it can be placed in a water bath and boiled safely.

How can I separate the glass fragments, salt and sugar? Describe all the important steps necessary for me to have glass (to throw away), and sugar and salt (to use in experiments, not to eat).

A Scale Diagram of the Planets

In class we will draw scale diagrams of all the planets.

Homework (due Tuesday Jan 31st): Calculate the size of Earth and your planet or pluton (on the shared Gdoc) so that they can be drawn to scale on an A3 piece of paper.

You may use this Gdoc spreadsheet, but you don’t have to. If you wish to use this one, instructions are below. Adjustments will need to be made for the rings of Saturn or Charon (if you are doing Pluto).

2. Enter the name of your planet (F1)
4. Enter the radius of each layer in the cells F3 to F6. You do not need to use all of these cells if your planet does not have this many layers. You can also add more rows if you need more layers.
5. Enter the size you want Earth to be (in centimetres) in C7. Check the size of your planet in G7. If Earth and your planet can both fit on an A4 piece of paper, you have finished. If not, try a different size for Earth, and keep trying until you have sizes which can fit on an A43 piece of paper. They should take up most of the page but allow some space for labels, interesting facts, a border etc.

You only need to change numbers highlighted in yellow (unless you are modifying this to calculate the size/s of moons, rings etc).

Note that planets are not spherical (largely because they rotate) however the differences between polar (to the north or south poles) and equatorial (to the equator) radii are generally small enough that we can consider them negligible and ignore them. It’s best to use an average radius for each measurement, but it doesn’t really matter for this exercise.

Please also note that for layers of the Earth, “inner core, outer core, mantle and crust” are fine; I don’t expect you to use the asthenosphere, lithosphere etc (but you can if you want to). If you don’t know what this means, please ignore this.

Please also remember that if you are doing a gas giant you will need to also have another, bigger diagram of Earth to show the layers, but this one does not need to be to scale.