Sexual reproduction mixes two genomes, certainly. But to take eye color as a well-known example; you might have a parent with brown eyes, and the other parent with blue eyes. Yours will be one or the other, but as brown eyes are "dominant", you would have needed to inherit a recessive (and hidden) blue eye gene from the brown eyed parent.
In other words, for one parent to have blue eyes, both genes she carries (I'll just pick a gender here) must be for blue eyes. If either one was brown, she'd have brown eyes instead.
The other parent [i]has[/i] brown eyes, but this means either that both genes code for brown eyes, or that one of them is a hidden blue.
Offspring get one gene from each parent.
Offsping in the first case can only be "brown-blue", which means that they will ALL carry the recessive blue-eyed gene (and can pass it on) but all will have brown eyes.
However, if the brown-eyed parent is "mixed", theoretically half of the offspring with a blue eyed other parent will have blue eyes.
Side note: Genetic odds don't really work with small numbers; there could be ten brown eyed children or ten blue eyed or any combination. Now if they had [i]lots[/i] of kids, it'd work out. But their finances wouldn't. ];)
I've over-simplified the eye color business, but this is how it works in principle. Throw green eyes and hazel eyes in the mix and it gets more difficult to see clearly.
In any event, picture a useful trait such as a longer than usual neck, or a slower metabolism, or a whatever might be useful in the circumstances happening to occur. (Or, a neutral trait such as brown eyes.) If this is associated with a dominant gene, it will take only one parent to pass it on.
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timeasmymeasure
Re:
Date: 2002-11-19 07:41 am (UTC)In other words, for one parent to have blue eyes, both genes she carries (I'll just pick a gender here) must be for blue eyes. If either one was brown, she'd have brown eyes instead.
The other parent [i]has[/i] brown eyes, but this means either that both genes code for brown eyes, or that one of them is a hidden blue.
Offspring get one gene from each parent.
Offsping in the first case can only be "brown-blue", which means that they will ALL carry the recessive blue-eyed gene (and can pass it on) but all will have brown eyes.
However, if the brown-eyed parent is "mixed", theoretically half of the offspring with a blue eyed other parent will have blue eyes.
Side note: Genetic odds don't really work with small numbers; there could be ten brown eyed children or ten blue eyed or any combination. Now if they had [i]lots[/i] of kids, it'd work out. But their finances wouldn't. ];)
I've over-simplified the eye color business, but this is how it works in principle. Throw green eyes and hazel eyes in the mix and it gets more difficult to see clearly.
In any event, picture a useful trait such as a longer than usual neck, or a slower metabolism, or a whatever might be useful in the circumstances happening to occur. (Or, a neutral trait such as brown eyes.) If this is associated with a dominant gene, it will take only one parent to pass it on.
Make sense?
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