Google Answers Logo
View Question
Q: Basic Genetics ( Answered,   0 Comments )
Subject: Basic Genetics
Category: Science > Biology
Asked by: operator-ga
List Price: $2.00
Posted: 14 Jun 2004 14:11 PDT
Expires: 14 Jul 2004 14:11 PDT
Question ID: 361042
In cocker spaniels, solid color (A) is dominant over spotted (a), and
black coat color (B) is dominant over red (b). If two solid black dogs
were crossed several times and the total offspring were eighteen solid
black and five spotted black puppies, the genotypes of the parents
would most likely be
a. Aa Bb x AA Bb 
b. Aa BB x aa Bb 
c. Aa Bb x Aa Bb 
d. AA BB x Aa Bb 
e. aa Bb x AA Bb
Subject: Re: Basic Genetics
Answered By: librariankt-ga on 15 Jun 2004 12:42 PDT
Hi Operator,

Me again.  I just love these genetic cross questions!

This one is b: AaBB X AaBb

Let's approach this one from the point of view of knocking out our
options.  First of all, all the offspring are solid black, which means
at least one of the parents has to be homozygous for the dominant (B)
allele - the puppies may be heterozygous, we really don't care.  We
also don't care whether the other parent of homozygous or
heterozygous, since all the puppies will end up black either way. 
That means that the answer has to be either b or c.

Second, we know that roughly 1/4th of the offspring (remember that in
real life statistics is approximate) are homozygous for the recessive
spotty allele (a).  That means that we have a classic 3:1 ratio of
phenotypes, indicating two heterozygous parents.

Thus, our answer is AaBB by AaBb.

Yours, Librariankt
There are no comments at this time.

Important Disclaimer: Answers and comments provided on Google Answers are general information, and are not intended to substitute for informed professional medical, psychiatric, psychological, tax, legal, investment, accounting, or other professional advice. Google does not endorse, and expressly disclaims liability for any product, manufacturer, distributor, service or service provider mentioned or any opinion expressed in answers or comments. Please read carefully the Google Answers Terms of Service.

If you feel that you have found inappropriate content, please let us know by emailing us at with the question ID listed above. Thank you.
Search Google Answers for
Google Answers  

Google Home - Answers FAQ - Terms of Service - Privacy Policy