ihatescience56
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Im sooo confused. If anyone can guide me through these questions.

1) in mice, white fur is dominant. What typenof offspring would you expect from a cross between heterozygous individual and one with grey fur? Explain your answer with a genetic diagram. (Monohybrid cross)

What im getting from this is if white fur is dominant then let it be W. But what letter would i take for the grey fur? a small w? Or a small g?
And would the heterozygous individual be: Ww and the one with grey fur be : ww
So my cross would be Ww*ww ?

2) haemophilia is a genetic disorder where the faulty gene is located on the X chromosome. A female carrier has children with a healthy male. Explain using a punnet square the probability of having healthy, carrier or affected children. Can they have an affected daughter? Can they have an affected son? Explain the diff.

Gahhh, what even is this??
Would the female carrier be X^hX ( X with a small h at the top for haemophilia) and another X. And the male is XY. I dont get it???
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ihatescience56
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Anyone??
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ihatescience56
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Can anyone help?!
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AFStudent
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(Original post by ihatescience56)
Im sooo confused. If anyone can guide me through these questions.

1) in mice, white fur is dominant. What typenof offspring would you expect from a cross between heterozygous individual and one with grey fur? Explain your answer with a genetic diagram. (Monohybrid cross)

What im getting from this is if white fur is dominant then let it be W. But what letter would i take for the grey fur? a small w? Or a small g?
And would the heterozygous individual be: Ww and the one with grey fur be : ww
So my cross would be Ww*ww ?

2) haemophilia is a genetic disorder where the faulty gene is located on the X chromosome. A female carrier has children with a healthy male. Explain using a punnet square the probability of having healthy, carrier or affected children. Can they have an affected daughter? Can they have an affected son? Explain the diff.

Gahhh, what even is this??
Would the female carrier be X^hX ( X with a small h at the top for haemophilia) and another X. And the male is XY. I dont get it???
I did this last year but I believe I still remember. You're correct on both questions. Grey fur is recessive so it would be a w, not g.

For the second question:
Make a punnet square with X^hX*XY
Look at the combinations and you will be able to answer the following questions.
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ihatescience56
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(Original post by AFStudent)
I did this last year but I believe I still remember. You're correct on both questions. Grey fur is recessive so it would be a w, not g.

For the second question:
Make a punnet square with X^hX*XY
Look at the combinations and you will be able to answer the following questions.
Thanks for the reply!

If you can help me with this question too:

Both my parents have brown eyes but i have blue eyes. Explain how this can be using a punnet square.

I would have crossed Bb *Bb and would have got 1/4 bb which is blue eyee but the question says its a dyhybrid cross so im confused?!
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AFStudent
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(Original post by ihatescience56)
Thanks for the reply!

If you can help me with this question too:

Both my parents have brown eyes but i have blue eyes. Explain how this can be using a punnet square.

I would have crossed Bb *Bb and would have got 1/4 bb which is blue eyee but the question says its a dyhybrid cross so im confused?!
Is there another part to the question? I thought dihybrid crosses are used when there is more than one characteristic e.g. blue vs brown eyes and freckles vs no freckles.

OR it could be like this:

BB = brown
Bb = brown
as brown is dominant and the question doesn't tell you whether they are homozygous or heterozygous

As one 'b' or 'B' does not mean anything. So you'd cross them like so:
BB*Bb*BB*Bb

Edit: oml tsr is messing up my formatting
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ihatescience56
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(Original post by AFStudent)
Is there another part to the question? I thought dihybrid crosses are used when there is more than one characteristic e.g. blue vs brown eyes and freckles vs no freckles.

OR it could be like this:

BB = brown
Bb = brown
as brown is dominant and the question doesn't tell you whether they are homozygous or heterozygous

As one 'b' or 'B' does not mean anything. So you'd cross them like so:
BB*Bb*BB*Bb

Edit: oml tsr is messing up my formatting
Nope. All it says after that is: the mother is pregnant again. What is the probability that she has another "boy" with "blue eyes"? Huh?! And the "boy" and "blue eyes" are in bold so i don't know if that's supposed to give me some sort of clue.

If i crossed BB*Bb brown eyed parents i wouldn't get a blue eyed child as blue eyes is recessive (bb). I would get BB, BB, Bb and Bb and these are all brown eyed children as they have the dominant brown eyed gene. Right?

Sooo confused fml
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AFStudent
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Sorry about the late reply, I quickly went to eat dinner.

I'm really confused on why it's asking for a dihybrid cross. It should just be Bb*Bb
Sorry I seem to have forgotten everything I'd learnt last year
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ihatescience56
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(Original post by AFStudent)
Sorry about the late reply, I quickly went to eat dinner.

I'm really confused on why it's asking for a dihybrid cross. It should just be Bb*Bb
Sorry I seem to have forgotten everything I'd learnt last year
Hey, it's ok. Thanks ever so much for the help

And yup, i've got it now.
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Rorschach II
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(Original post by ihatescience56)
Anyone??
(Original post by ihatescience56)
Can anyone help?!
Spam
.
.
My exam board doesn't do dihybrid crosses questions, but for your last question, the only way you can have blue eyes if your parents had brown would be if they were heterozygous.

(You were correct.)

Blue eyes needs homozygous recessive (bb)
So you'd need Bb and Bb in your parents for the chance to have blue eyes.

Otherwise it wouldn't be possible.
.
.
Perhaps that part of the question was just unrelated to the dihybrid cross in the original part.
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ihatescience56
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(Original post by XcitingStuart)
Spam
.
.
My exam board doesn't do dihybrid crosses questions, but for your last question, the only way you can have blue eyes if your parents had brown would be if they were heterozygous.

(You were correct.)

Blue eyes needs homozygous recessive (bb)
So you'd need Bb and Bb in your parents for the chance to have blue eyes.

Otherwise it wouldn't be possible.
.
.
Perhaps that part of the question was just unrelated to the dihybrid cross in the original part.
Spam? I was only bumping up the thread....

Yup, i got it. I guess it was. What exam board do you do? I'm doing ocr.

Thanks anyway
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Smonnie
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I know nothing about this topic.
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Rorschach II
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(Original post by ihatescience56)
Spam? I was only bumping up the thread....

Yup, i got it. I guess it was. What exam board do you do? I'm doing ocr.

Thanks anyway
But you didn't wait... (a while)

AQA.

You're welcome.
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ihatescience56
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(Original post by Smonnie)
I know nothing about this topic.
What was the point of replying? :eek3:
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ihatescience56
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(Original post by XcitingStuart)
But you didn't wait... (a while)

AQA.

You're welcome.
Oh, i did though. A good 30-40 minutes. If i hadn't bumped it, it would have gone unnoticed. :unimpressed:

I hate bio So much memorisation
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