Beginning Genetics Learner trying to understand these two problems and find the ans.!

[Powerbook]

So, I for the life of me cannot put two to two together with these two questions. I don't know whether the formatting of the website is confusing me or not. If someone could work through these problems with me and explain, I would very much appreciate it. The website on the bottom of the post shows the genotypes.

 

 

 

reeding #1

 

 

Morganne is an orange roan (orange with a brown nose). Her mother

Lexie was an orange roan (orange with a brown nose). Lexie was bred

to Valor - a blue Belton (black with a black nose).

 

Give the possible genotypes of Morganne, Lexie, and Valor. Explain.

 

 

 

 

Breeding 2

 

 

Belle is a tricolor with a black nose. Her mother was Lexie, the

orange roan. This time Lexie was bred to Noble, a tricolor with a

black nose.

 

 

Give the possible genotypes of Belle, Lexie, and Noble. Explain.

 

 

 

 

http://www.healthgene.com/canine/C128_setter_english.asp

[curiouslou]

Well if i am right this is rather simple...i think.

 

BREEDING #1

 

if you look at the table (C128EB) in the given website you can see that a dog with an orange coat can have either a black or brown nose. As the dog Morgan is Orange with a brown nose we can see that there is only one genotype that matches this description. that is "eebb". If you look you will see that the lower case of the allele shows that it is a recessive gene. Same thing with Lexie. Once again standard procedure follows for Valor, however one can include the KK alleles, although i am not sure if this is 100% necessary. although i have been wrong.

 

I think my answer is correct, i perhaps i misread, i am still studying bio myself.

[CharonY]

Essentially you are on the right track. This has more to do with logic than actual genetics (well except knowing what recessive and dominant traits are).

So essentially you have just to track down, which possible genotypes correspond to the observed phenotypes.

Morganne can only be eebb as noted correctly as her mother, as these are the only genotypes that allow orange with brown nose.

However Valor (the father) has four options:

EEBB

EeBB

EEBb

EeBb

 

However, only in case can Valor be the father of Morganne. Which is it?

[Geshenk]

Hello pb, hope you have it sussed by now. If not, I hope the following is of some help. I think you are right in that the Healthgene formatting is a bit confusing. They list two different terms for the ee genotype - orange and red. There are various terms for this colour across the breeds but 'orange' is the usual one for English Setters. And on a quick glance, I've seen at least two mistakes in the table, in the 'hidden color' column.

 

These are the possible genotypes -

 

Morganne and Lexie

 

bb ee

These are the only two genes that we can be sure of. The K locus isn't known because ee is epistatic and overrides almost all others. We can be sure of bb because this shows in the nose pigment. A black nose would have to be Bb or BB.

 

Valor

 

Could be various genotypes, too many to list but what we can be sure of is that he is -

 

B_ E_ KB_

 

The second allele of each of those loci could be a repeat of the same or the recessive (for this breed) - b, e, ky. Any combination of these recessives coupled with those three dominants will give a blue belton with black pigment and without the tricolour pattern.

 

Belle

 

Bb E_ kyky

 

She has black pigment so has to be B (from her sire), and the b is from her dam Lexie. Dominant E has to be present for normal distribution of black pigment, but we don't know the second allele on that locus, it could be E or e. And kyky is the only gene combination that allows expression of tanpoint pattern (tricolour) in this breed.

 

Noble

 

B_ E_ kyky

 

Same as for Belle except that we don't know his second B locus allele.

Edited September 6, 2008 by Geshenk