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Q: Genetic Formula ( Answered 5 out of 5 stars,   1 Comment )
Subject: Genetic Formula
Category: Science > Biology
Asked by: jennifer1000-ga
List Price: $2.00
Posted: 04 Oct 2004 22:29 PDT
Expires: 03 Nov 2004 21:29 PST
Question ID: 410451
In cattle, the hornless condition is called polled and is due to a
dominant gene, while having horns results from a homozygous recessive
condition. The red and white coat colors are intermediate and give a
roan color when the fenes are heterozygous. What is the phenotypic
ratio of a cross between two cattle heterzygous for both horns and
Subject: Re: Genetic Formula
Answered By: librariankt-ga on 05 Oct 2004 06:27 PDT
Rated:5 out of 5 stars
Hi Jennifer,

Here's what I'll call our gene alleles this time:  
Polled (dominant): P vs. hornless (recessive): p
Red: R vs. white: r - remember that you have three possible phenotypes
for color: RR=red Rr=roan and rr=white

Like in the guinea pigs question, we have two heterozygous animals
producing offspring:

PPRR (1) - Polled, red
PPRr (2) - Polled, roan
PPrr (1) - Polled, white
PpRR (2) - Polled, red
PpRr (4) - Polled, roan
Pprr (2) - Polled, white
ppRR (1) - horned, red
ppRr (2) - horned, roan
pprr (1) - horned, white

So now we just need to count up the numbers in parentheses to
determine the ratio.  Since we have not four phenotypes (as with the
guinea pigs) but six, things are a bit more complicated:

Polled, red - 3
Polled, roan - 6
Polled, white - 3
Horned, red - 1
Horned, roan - 2
Horned, white - 1

Again, check those basic Mendelian genetics links that I gave you
earlier for more help on genetic crosses using incomplete dominance -
or ask for more clarification if you need it!  I really enjoy these
brain teasers, as I think of them, possibly because I don't have to do
them for school any more!  ;)

jennifer1000-ga rated this answer:5 out of 5 stars and gave an additional tip of: $1.00

Subject: Re: Genetic Formula
From: politicalguru-ga on 05 Oct 2004 01:13 PDT
Thank you for your question.  
However, I believe that to answer it well, your question will require
more time and effort than the average amount of time and effort
associated with this price. Here is a link to guidelines about pricing
your question, in the pricing guide:

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