If one of the genes of a pair can produce by itself a characteristic of the
phenotype, the gene is said to be
t. If both genes must be the same to
produce a characteristic, the genes are
e. If an individual has one recessive
and one dominant gene in a pair, the ultimate characteristic is determined by the
If the two genes for a trait are the same, we say that the individual is
for that trait. If the two genes are different, the individual is
zygous for that trait.
If two twins in a set are different, they are called
al twins. If two twins in
a set resemble each other very closely, they are called
al twins and have the
Consider an imaginary situation in which humans have a gene pair which
determines whether they will grow a pair of antennae. Assume that A, the gene for
antennae, is dominant and that a, the gene for no antennae, is recessive. Among all of
the children of parents having a genotype of Aa, what percentage of the children will
Consider the situation in exercise 8 above. Also assume that there is a gene pair
which determines whether humans will have four upper members or only two. Assume
that B is the dominant gene for four upper members and that b is the recessive gene for
two upper members. Among all of the children of parents having a genotype of Aa Bb,
what fraction will have both antennae and four upper members?
What fraction will have antennae and two upper members?
What fraction will have four upper members but no antennae?
In incomplete dominance, what relationship is seen among the potential
What is complementary inheritance?
What is multifactorial inheritance?
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