Inductive Punnett Squares

Inductive Punnett Squares

Learning from patterns

Welcome to the Punnett Square inductive lesson.

• Pay attention to the patterns you see here.

• Learn from them and try to guess how they work.

• By the end of this lesson, you should be able to complete basic Punnett Squares.

Part 1:

The basics of the square

Let's see if you caught the patterns.

Multiple Choice

What should go in box 1?

Multiple Choice

What should go in box 2?

Good. Now let's try a different Punnett Square.

Multiple Choice

What should go in box 1?

Multiple Choice

What should go in box 2?

Multiple Choice

What should go in box 3?

Multiple Choice

What should go in box 4?

Are you catching the pattern?

The items from the top and left are combined to get the internal squares.

In this case, the second square gets a blue from the top and a red from the left.

One last test before we move on.

Multiple Select

Which patterns are NOT going to be found in this Punnett Square?

Hopefully that was fine. Now let's try going in reverse.

Multiple Choice

What should go in box 1?

Multiple Choice

What should go in box 2?

Multiple Choice

What should go in box 3?

Multiple Choice

What should go in box 4?

How was that?

This pattern is just the reverse of the last.

The shapes in the middle have to come from the top and left.

Now let's add some elements.

Part 2:

Starting the square

Let's see if you caught the patterns.

Multiple Choice

What should be in box 1?

Multiple Choice

What should be in box 2?

Multiple Choice

What should be in box 3?

Multiple Choice

What should be in box 4?

Let's try another one.

This can be tricky, so good luck!

Multiple Choice

What should be in box 1?

Multiple Choice

What should be in box 2?

Multiple Choice

What should be in box 3?

Multiple Choice

What should be in box 4?

Good work.

The items on the top come from the father and the items on the left come from the mother.

Put it together.

Using the things you've already learned, you can put everything together into a complete Punnett Square.

This completed square shows every possible combination of the mother and father's shapes.

Part 3:

Homo v Hetero

You might not know these next words, but give them a try.

Multiple Choice

Homo or Hetero?

• Homo

• Hetero

Multiple Choice

Homo or Hetero?

• Homo

• Hetero

Multiple Choice

Homo or Hetero?

• Homo

• Hetero

What does it mean?

• Homo and Hetero are prefixes which indicate similarity.

• Homo = same or identical

• Hetero = different

Let's check again.

Multiple Choice

Homo or Hetero?

• Homo

• Hetero

Multiple Choice

Homo or Hetero?

• Homo

• Hetero

Now some synthesis...

Multiple Choice

Are the father's shapes homo or hetero?

• Homo

• Hetero

Multiple Choice

Are the mother's shapes homo or hetero?

• Homo

• Hetero

Multiple Choice

How many of the middle boxes of the Punnett square are homo?

• 0

• 1

• 2

• 3

• 4

Multiple Choice

How many of the middle boxes of the Punnett square are hetero?

• 0

• 1

• 2

• 3

• 4

Alright, good work.

If you've made it this far, you deserve a break.

Studies have shown that breaking up a study session can help memory!

When you continue, we'll replace the shapes with letters and try again.

Part 4:

Adding Alleles

What is an allele?

Alleles are "versions" of a gene. We usally represent them as letters.

Humans (and other diploid species) have two copies of every gene.

Most often, an individual receives one set of DNA from their mother and one from their father.

Sometime the alleles for their genes are the same (homozygous) and sometimes they are different (heterozygous).

For example...

Human eye colors are complicated, but one of the major genes controls the blue or brown color.

The brown eye gene is represented by the letter B.

The blue eye gene is represented by the letter b.

Let's see if you caught the pattern.

Hint: Think back to the shapes from earlier.

Multiple Choice

What should go in box 1?

• DD

• Dd

• dD

• dd

Multiple Choice

What should go in box 2?

• DD

• Dd

• dD

• dd

How was that?

It's the same pattern!

Just like before, the pieces from the top and the left come together for the middle squares.

But did you notice how the capital letter always comes first?

That's a convention used by genetic scientists. We always keep the same letters together, with the capital first.

AaBbCcDd = Right

aAbBcCdD = Wrong

Time for some more practice!

Multiple Choice

What should go in box 1?

• RR

• Rr

• rR

• rr

Multiple Choice

What should go in box 2?

• RR

• Rr

• rR

• rr

Multiple Choice

What should go in box 3?

• RR

• Rr

• rR

• rr

Multiple Choice

What should go in box 4?

• RR

• Rr

• rR

• rr

How about a more complicated square?

Multiple Choice

What should go in box 1?

• GG

• Gg

• gG

• gg

Multiple Choice

What should go in box 2?

• GG

• Gg

• gG

• gg

Multiple Choice

What should go in box 3?

• GG

• Gg

• gG

• gg

Multiple Choice

What should go in box 4?

• GG

• Gg

• gG

• gg

Did you match it all correctly?

Remember that the capital letter always comes first.

(Bb not bB)

Let's bring back some synthesis.

Remember working with the shapes from the mother and father?

Time to check. Good luck!

Multiple Choice

What should go in box 1?

• D

• d

Multiple Choice

What should go in box 2?

• D

• d

Bringing them down.

The father's alleles (letters) go in the top two boxes.

Where will the mother's alleles go?

Multiple Choice

What should go in box 3?

• D

• d

Multiple Choice

What should go in box 4?

• D

• d