Horned Genetics

Does anyone know how horned genetics travel, if they are recessive or jut pop up randomly? I'm asking  because we used WS A Step Up in a flush and have 2 calves (both sexes) that have horns. I looked back at the pedigrees (the cow is also PB Sim) and found a few shot of horns on both the sire and dam.

P = Polling Gene (dominant)
p = Horning Gene (recessive)
PP = Homo Polled (commonly referred to as smooth polled)
Pp = Hetero Polled (meaning, carrying a horn gene, but is polled....or could be scurred))
pp = Homo Horned (thus, yields a horned animals)

Look here for a good explanation:
http://homepage.usask.ca/~schmutz/polled.html

I'm far removed from my days in south Alabama, when some Brahman influence was helpful.  Thought was that some Zebu cattle also carried an 'African horn gene', that might confound things...but haven't seen any recent work on that...

http://www.cals.ncsu.edu/an_sci/extension/animal/news/aug96/aug96-3.html

Table 1. Genetic Expression of Polledness or Horns and Expected Inheritance by Offspring
Sire Dam Calves

Homozygous polled (PP) Homozygous polled (PP)
100% Homozygous polled (PP)

Homozygous polled (PP)  Heterozygous polled (Pp)   
50% Homozygous polled (PP)
50% Heterozygous polled (Pp)
                                         
Homozygous polled (PP) Homozygous horned (pp)
100 % Heterozygous polled (Pp)

Heterozygous polled (Pp) Homozygous horned (pp)     
50% Heterozygous polled (Pp)
50% Homozygous horned (pp)
   
Heterozygous polled (Pp)      Heterozygous polled (Pp)   
25% Homozygous polled (PP)
50% Heterozygous polled (Pp)
25% Homozygous horned (pp)

OH put it right on the money.  Heterozygous polled x Heterozygous polled will give you 25% horned calves.  I was a bit disappointed when I got a horned MAB calf out of a polled cow.  Time to get out the Dr. Naylers!

The African horn gene does exist in Zebu derived cattle (Brahma) and in Texas Longhorns, as well as some of the Sanga type cattle. It is dominant to both the polled gene (PP) and the recessive horned gene (pp). It can really throw a wrench in the genetic equation.

How is the African horn gene expressed? What makes it different than the regular horned gene?

I think it expresses it as more of a scur. I know one time I think he had a heck of a conversation on here on this subject. I think you can have a homozygous polled bull.......with scurs.

Inheritance of African horn gene is similar to that of scurs...and some recent papers have indicated that they are the same gene...perhaps some other Zebu genes influence expression.  At any rate, it's a sex-influenced trait - males with one or two copies will have scurs or African horn; females must have two copies in order to express scur/African horn growth.

AJ, I used to think that too, but to my knowledge, but look here, and ponder it a while:http://homepage.usask.ca/~schmutz/ScurredTable.html

All the recent investigations have pretty well shown that only hetero-polled animals will express scurs.  Homozygous polled even masks homozygosity for scurs...so, a smooth-polled(homo-polled) bull could potentially sire scurred calves from a smooth-polled (but hetero-polled)cow that is a scur carrier, if he's a scur carrier.
I see reports of purebred Angus bulls occasionally siring scurred calves...making folks question his 'purity'; There were scurred Angus bulls in the foundation stock of the breed - Hanton 80 and Shah, perhaps others; so...in a homo-polled breed, the scur gene may have been skating along undetected for generations...until it pops up when you breed 'em to a hetero-polled cow. So...maybe the dams of those scurred 'Angus' calves should be the ones whose 'purity' is questioned...

interesting article on spontaneous polled event and other implications.

https://pubmed.ncbi.nlm.nih.gov/33046754/