Genetics question

Fraggr

Fraggr

Fraggr

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Kinda confused about symbols.

A question on my homework sheet says "in rabbits, the allele for brown coats is dominant to the allele for white coats. Write down suitable symbols for these two coat colours."

I am not sure if it should be BrBr whwh or Brbr whwh. Any help?
 
Fraggr said:
But what would the brown parent have?
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Hmm, well if both parents were Brown then they'd either have BB or Bw but they'd both pass on the B allele because it is dominant. If there was 1 Brown and 1 white parent they'd still have the B allele for a brown child. You'd need 2 white parents to have a white rabbit because it's the recessive gene.

I think.
 
RandomTom said:
Hmm, well if both parents were Brown then they'd either have BB or Bw but they'd both pass on the B allele because it is dominant. If there was 1 Brown and 1 white parent they'd still have the B allele for a brown child. You'd need 2 white parents to have a white rabbit because it's the recessive gene.

I think.
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I reread the question to myself, and I think it just wants to know what letter you should use for brown and white :o

Br/B and wh/w is the answer. :D I thought it was more complicated than it actually is...
 
You should always write the dominant gene as a capital letter with the recessive gene as the lower case letter used for the dominant gene. So if brown is dominant over white it should be written as Bb.

So you would have BB for Homozygous brown, Bb for Heterozygous brown and bb for Homozygous white.
 
Redwalar said:
You should always write the dominant gene as a capital letter with the recessive gene as the lower case letter used for the dominant gene. So if brown is dominant over white it should be written as Bb.

So you would have BB for Homozygous brown, Bb for Heterozygous brown and bb for Homozygous white.
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Yeah, I know. I just had a moment of temporary retardation there. :p
 
RandomTom said:
Hmm, well if both parents were Brown then they'd either have BB or Bw but they'd both pass on the B allele because it is dominant. If there was 1 Brown and 1 white parent they'd still have the B allele for a brown child. You'd need 2 white parents to have a white rabbit because it's the recessive gene.

I think.
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Not quite, 2 brown rabbits could have a white offspring if both carried the recessive allele. You have 2 brown rabbits Bw and Bw If they bred you would get 4 possible outcomes.

BB
Bw
wB
ww

The only one of those 4 to be white would be the last one, so a 1 in 4 chance of having white offspring.

If there were 2 white rabbits there would be no chance of them having brown offspring though as they will not have the allele (or they would be brown).
 
Redwalar said:
So you would have BB for Homozygous brown, Bb for Heterozygous brown and bb for Homozygous white.
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Yup. If you're writing it properly, you should be using the same letters - so B and b rather an B and w, as quoted.

A brown phenotype would be BB, Bb or bB, with white being bb.
 
A.N.Other said:
Yup. If you're writing it properly, you should be using the same letters - so B and b rather an B and w, as quoted.

A brown phenotype would be BB, Bb or bB, with white being bb.
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Yeah, that's how I would do it. (I have been doing genetics it in Biology recently).

Angus Higgins
 
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