Question

punnett squares help?

Answer 1

What is it that you don't understand?

Answer 2

Each square is 25%. The parents are both heterozygous, which means they carry, but don't show, recessive traits. How many of their children are heterozygous as well?

Answer 3

Oops, scratch that. They're asking about phenotypes. How many homozygous dominant and heterozygous offspring are there?

Answer 4

I am bad at punnett squares... and learning them

Answer 5

That's fine!

Answer 6

I love explaining them. The dominant trait is the big R, while the recessive trait is the little r. Whenever you have a heterozygous parent, you have a big R and a little r, Rr.

Answer 7

so then wouldnt the answer be 50%?

Answer 8

A heterozygous parent will carry the recessive trait and show the dominant trait, since big R almost always beats little r.

Answer 9

No, you're looking at the genotype. They're asking about the phenotype, how the offspring will look.

Answer 10

Let's say the big R is a red flower and the little r is a white flower. We won't go into incomplete dominance, since that's probably later in the unit. When the parent is RR, they are red; when a parent is Rr, they are red; and when a parent is rr, they are white.

Answer 11

Both parents are Rr, so their offspring include one RR, two Rr, and one rr. Based on what I just told you, how many of those offspring will be red?

Answer 12

3?

Answer 13

Yep, and what percent is 3/4?

Answer 14

so then 75%?

Answer 15

Yep :)

Answer 16

Thank you so much. Could you help me some more?

Answer 17

Sure, I love genetics.

Answer 18

would this be 25%?

Answer 19

Yep :) Nice job

Answer 20

Do you know how to set up a Punnet square?

Answer 21

kind of

Answer 22

You'll combine the two traits linked together in each box, like so:

Answer 23

I'm sorry if the drawing is confusing, I can't use differently colored pens ;-;

Answer 24

But you can see from it that there is one PP, two Pp, and one pp.

Answer 25

so im guessing the answer is D?

Answer 26

Yep, can you see why?

Answer 27

Okay. When you're writing a Punnet square, you put one one the parent's genotypes (Rr in this case) on top, and the other parent's genotype (also Rr) on the left side.

Answer 28

When you're going through each of the squares to write the offspring's genotype, you'll see whether there's a recessive or dominant trait above, then you'll look to see whether there's a dominant or recessive trait to the left.

Answer 29

You completely ignore the other offspring's squares, only looking at the parents' genotypes. If you see one dominant trait (big R) above and one recessive trait (little r) to the left, you'll write Rr in that square. If you see the little r above and the big R to the left, you'll write the same thing.

Answer 30

Oh okay I get it I think lol

Answer 31

Awesome :) Let me know if you have any more trouble

Answer 32

I have 2 more questions I think on the same subject I need help with. I have them answered I just don't know if they are correct or not

Answer 33

Cool, shoot 'em.

Answer 34

^ that one I think is B

Answer 35

You got that one right with A, the Law of Dominance is Mendel's third law, and it basically says that any genotype that isn't homozygous recessive (tt) will show the dominant trait.

Answer 36

okay