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Mendelian Genetics
Crosses & Squares Questions


     Cross Review Questions:

1.  An experiment in probability required that two like coins be flipped simultaneously.  The results for 100 flips were recorded.  Which one of the following choices indicates the results to be expected?
     a.  two heads - 50%; two tails - 50%
     b.  two heads - 25%; one tail, one head - 50%; two tails - 25%
     c.  two heads - 25%; two tails - 75%
     d.  two heads - 50%; one head, one tail - 50%
     e.  two tails - 50%; one head, one tail - 50%

     2.  In guinea pigs, black is dominant.  One half of a particular litter is white.  If it is assumed that the laws of chance operate, the parent cross was ______.
     a.  BB * Bb
     b.  Bb * Bb
     c.  Bb * bb
     d.  bb * bb
     e.  BB * bb

     3.  As a result of crossing two hybrid yellow garden peas, 120 offspring are produced.  According to the laws of chance, the most probable number of yellow offspring is ______.
     a.  0
     b.  30
     c.  60
     d.  90
     e.  120

     4.  To determine whether an unknown black guinea pig is pure or hybrid black, it should be crossed with _______ guinea pig.
     a.  a white
     b.  a hybrid black
     c.  a hybrid white
     d.  a pure black
     e.  another unknown

     5.  In human beings, brown eyes are usually dominant over blue eyes.  Suppose that a blue-eyed man marries a brown-eyed female whose father was blue-eyed.  The percentage of their children with blue eyes would be closest to _______.
     a.  0
     b.  25
     c.  50
     d.  75
     e.  100

     6.  In a diploid organism with the genotype AaBBCCDDEE, how many genetically distinct kinds of gametes would be produced?
     a.  2
     b.  4
     c.  8
     d.  16
     e.  32

     7.  The sites of four gene loci on a chromosome are based on the following crossing-over frequencies:
     AB - 40%
     BC - 20%
     CD - 10%
     CA - 20%
     DB - 10%
Which of the following best represents the relative positions of the four genes?
     a.  A         CBD
     b.  A         CDB
     c.  A    D   C   B
     d.  A    C   B   D
     e.  A    B   C   D

     8.  Which of the following is true of a gene that is dominant?
     a.  It is usually harmful.
     b.  It will occur more frequently than its recessive allele.
     c.  It will occur less frequently than its recessive allele.
     d.  It is more likely to be passed on to the next generation than its recessive allele.
     e.  It will have the same phenotypic effect whether it appears in a homozygous or heterozygous condition.

     9.  ___________ is a genetic condition in which both the homozygous dominant and homozygous recessive phenotypes are expressed in the heterozygote.
     a.  Monohybrid Cross
     b.  Dominance
     c.  Codominance
     d.  Incomplete Dominance
     e.  Recombination

     10. ___________ is a genetic condition in which the heterozygote's phenotype is intermediate between that of both homozygotes.
     a.  Monohybrid Cross
     b.  Dominance
     c.  Codominance
     d.  Incomplete Dominance
     e.  Recombination

To check your responses, go to the Cross Answers page.

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