Ask A Scientist© Biology Archive

Can  a trait disappear for several generations and then
reappear? Why?
Gerry A Adams

Answer:
Gerry,
 
A general answer to your general question: YES!
 
This answer could be made more specific depending upon the trait
you are thinking about.  Since our genetic makeup consists of pairs
of chromosomes, there is a possibility that a person could have 1
showing a particular trait, the other lacking the trait:  given
our current understanding of genetics we can predict whether the
trait will be expressed.  This would have to be answered--per
trait-- as to whether the particular trait is dominant or recessive.
Briefly, for a recessive trait to be expressed, it must occur in
each of the pair of chromosomes.  The recessive trait would be hidden
by the dominant trait if either of the chromosomes possessed the
dominant trait.  Obviously if both chromosomes possess the dominant
trait, THAT is what would be expressed.
 
You can picture how a recessive trait, hidden by a dominant-
APPEARing individual, might be passed on through genetic material
at conception.  If both parents passed on the recessive trait, both of the
offspring's chromosomes for that trait would be recessive, and the
recessive trait would be expressed.  This could occur in several
combinations of either parent being Dd dD or dd, with the D being
the dominant trait and the d being the recessive trait.  Hope this helps!
Ric (rickru)