Many Genes Sometimes Control One Trait  ANSWERS

B.                GENERAL RULE  ---   (See #1 below and to the right!)

           1.    Since you have 2 biological parents, both the two pictured fly  C H R O M O S O M E S
      (One above the map and one below it) and the G E N E S  on them occur in pairs. 
      You know what a pair is  --  T W O   of a kind in length, shape and gene markings.

       A  1. (a)  Here we see three different chromosomes with specific genes (Ex. G1, T1, A1 etc.)
          identified on the top chromosome.  These chromosomes should each be shown in 
          P A I R S, but I can't control what images I find in web searches.  

                (b)  This pair of genes usually controls a  S I N G L E  trait, but there are exceptions to
           this rule.

                 (c)  This is Tongue  R O L L I N G   a single trait controlled by a single  P A I R  of genes.

                 (d)  Here's another trait controlled by only a  S I N G L E   pair of genes.  When your
                        hands are lined up this way, either your little fingers are straight or form a B E N T.

                 (e)  This pattern of one pair of genes controlling one trait is very common in human biology,
                        but that does not mean it is the only pattern of inheritance.

            2.   Sometimes M O R E     T H A N   one pair of genes control one inherited trait.  Here are
                 three common human traits that each controlled by  M U L T I P L E  pairs of genes.

                 (a)     Example 1 --  four pairs of genes regulate human S K I N  pigmentation.          
            On this world map, it seems that   E Q U A T O R I A L  world regions have people with
            the darkest pigmentation. 

                      (b)  Example 2 --  At least two pairs of genes regulate human  E Y E   pigmentation.  
                         (Some books say two and some say three!)
                         By far the least amount of deposited pigments (look at the density of spots in the iris
                        of the eye) occurs in people with which of the eye colors on the left? 
                        Your answer should be true  B L U E.

 (c)  Example 3  --  Many pairs of genes control human  H A I R  pigmentation.  This
  is a shaft from a person with light colored hair.

          Example 3 --  At least three  pairs of genes regulate human  H E I G H T 

Some people have tall genes from both sides of the family.  Would you believe both of this man's parents were basketball players?  It's true.  And Y A O
(Ming of course)   is about 7'6" as a result.  Sure looks like he got a lot of genes for  T A L L N E S S.

            And some people despite having normal parents end up with genes for 
      S H O R T N E S S  or at least genes for some hormone deficiency resulting
      in short stature.  .  

            This is Nelson DeLaRosa from the Dominican Republic.  He's the World's
      shortest person.  He gained fame during the 2004 baseball season when he
      visited another famous Dominican in Boston.  PEDRO  caught some heat for
      being photographed lifting Nelson up in the air.  Who knows; maybe that's why
     Boston did not resign him and he became a free agent and went to the Mets
     the next Spring.