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Help - Heterozygous vs Homozygous

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V_Key

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Boy that's a Mouth Full - Try Typing it

Heterozygous vs. Homozygous Loci and Dominant vs. Recessive Genes

When an individual has two identical genes at a locus, it is said to be homozygous (a zygote is a germ cell, e.g. an egg or sperm, and homozygous means the two have the same gene at the same locus). Individuals with different genes at a locus are heterozygous at that locus. For example, individuals that are AA are homozygous, and those that are Aa are heterozygous.

In a heterozygous locus, one of the genes might be dominant, which means that the trait it codes for will be seen and the trait coded for by the other gene (the recessive gene) will not be epxressed. For example, suppose A is dominant and a is recessive. That means whenever an organism has an A at the locus - either AA, Aa, or aA - the attribute coded by A is in effect. The only way the attribute coded by a is seen is if the organism is aa.

Encarta® World English Dictionary © 1999 Microsoft Corporation. All rights reserved. Developed for Microsoft by Bloomsbury Publishing Plc.

lo·cus n
1. a place where something happens
2. a set of points, the positions of which satisfy a set of algebraic conditions
3. the position of a gene in a chromosome

ho·mo·zy·gous adj
having two identical genes at the corresponding loci (AA) of homologous chromosomes

het·er·o·zy·gous adj
used to describe a cell or organism that has two or more different versions (alleles) of at least one of its genes. (Aa) or (aA)

re·ces·sive adj
1. used to describe a gene that produces an effect in an organism only when its matching allele is identical. (aA) + (Aa) or (AA) + (Aa)
2. used to describe a characteristic or trait determined by a recessive gene
3. tending to go backward or to recede

n
1. a recessive gene or trait
2. an organism that has a recessive gene or trait

dominant
“A” being dominant
“a” being recessive


I’m trying to understand - - in this instance “A” being the Color Black
Is this the way it works?

Bull + Cow = Get
AA + Aa = AA Black
AA + aA = Aa Black
AA + aa = Aa Black

Reference See:
Homozygous Paint Horses

http://www.google.com/search?client=safari&rls=en&q=Homozygous+Paint+Horses&ie=UTF-8&oe=UTF-8
 

V_Key

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Northern Rancher said:
AAXAa is the same as AAxaA- if I remember right 75 percenet would be AA Homozygous and 25 percent would be Aa heterozygous.

I thought so but not sure... That may help others

How does the Duliuter Gene fit in

AA X Ad ? or AD?

Paint Horses have many color patterens and a "Death Color Gene" (Overo with white over the back) as I understand it, thats why I made the link
 

Turkey Track Bar

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Northern Rancher said:
With the lethalwhite gene you get white coloured foals that die pretty soon after birth not sure if it's a diluter gene per se.

Where's "Doc" when we need him? :D

Aren't the lethal whites mutations??? I am probably wrong but I seem to remember something about that in genetics class....

TTB
 

greg

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Although promenant in overos can also occur with a tobiano,shortly after birth lethal whites develope colic and failure to pass feces and always die.....its a defective gene that has to do with white colour.I,ve bred alot of overo on overo but never got a lethal white just the luck of the draw,I have a palamino paint stud I want to breed this year my only fear is his two glass eyes.
 

Northern Rancher

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I've only seen one 'white' foal in my travels but they don't last very long. Mamn I hate fish eyed paints-I own a couple but I hate them lol.
 

txag

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V_Key said:
I’m trying to understand - - in this instance “A” being the Color Black
Is this the way it works?

Bull + Cow = Get
AA + Aa = AA Black
AA + aA = Aa Black
AA + aa = Aa Black

Homozygous Black Bull (BB) to Heterozygous Black Cow (Bb), all offspring will be black. 50% will be homozygous black and 50% will be heterozygous black (carry the red gene).

Homozygous Black Bull (BB) to Heterozygous Black Cow (bB) will give you the same thing.

Homozygous Black Bull (BB) to Red Cow (homozygous bb), all offspring will be black. All will be Bb (carry the red gene).

Heterozygous Black Bull (Bb) to Heterozygous Black Cow (Bb) will give you 25% homozyous black (BB), 50% heterozygous black (Bb), and 25% red (bb).
 

txag

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V_Key said:
How does the Duliuter Gene fit in

the diluter is a gene at a totally different loci than the color genes for black and red. It is expressed as a dominant gene, so an animal only needs one copy of it for their color (red or black) to be diluted to a lighter red or smokey.
 

greg

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Had my city girl niece out one day she was awwwwing" your horse is blind."....had to explain the glass eye thing.
 

DOC HARRIS

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greg said:
Had my city girl niece out one day she was awwwwing" your horse is blind."....had to explain the glass eye thing.
Wow, Greg - I'll bet that was an exercise in futility! I can just picture the blank stares that she gave you about two sentences into the explanation. Sort of like - "glass eyes"! :shock:

DOC HARRIS
 

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