GENETICS EXAM 3 PRACTICE QUESTIONS
AND DETAILED SOLUTIONS
◉ When multiple genes contribute to the expression of a phenotype
they are called ________.
Answer: additive alleles
◉ How many gene pairs are involved in generating a typical
1:4:6:4:1 ratio.
Answer: 2
◉ Bell-shaped distributions produced by plotting results of F2 and
F3 crosses are typical of which type of inheritance.
Answer: multiple-factor inheritance
◉ To estimate how much the means of a variety of like samples
drawn from the same population might vary, what statistic is often
used?.
Answer: standard deviation of the mean
◉ Define the term broad-sense heritability (H2)..
Answer: Broad-sense heritability (H2 ) refers to the degree to which
phenotypic variation is due to genetic factors.
,◉ What is implied by a relatively high value of H2?.
Answer: A very high value of H2 indicates that the environment had
a relatively low impact on genotypic variation.
◉ Choose aspects of broad-sense heritability in equation form..
Answer: VP = VE + VG + VGE
◉ Interpret the meaning of an H2 (broad-sense heritability) value
that approaches 1.0..
Answer: Almost all the phenotypic variation is determined by
environmental factors.
◉ What is the name of the process of selecting a specific group of
organisms from an initially heterogeneous population for future
breeding purposes?.
Answer: artificial selection
◉ Expression QTL mapping allows researchers to characterize
________..
Answer: loci that control gene expression
◉ How do we know that threshold traits are actually polygenic even
though they may have as few as two discrete phenotypic classes?.
, Answer: -Polygenic conditions involving thresholds occur if a range
of expression is possible, but the trait is either expressed or not
expressed.
-Environmental factors have a considerable impact on polygenic
system, and therefore, on expression of threshold traits.
Submit
◉ How can we ascertain the number of polygenes involved in the
inheritance of a quantitative trait?.
Answer: -1/4^n, where n=the number of polygenes if the ratio of F2
individuals resembling either of the two extreme P1 phenotypes can
be determined
-(2n+1), where (2n+1) is the number of possible phenotypes and n
equals the number of additive loci
◉ What findings led geneticists to postulate the multiple-factor
hypothesis that invoked the idea of additive alleles to explain
inheritance patterns?.
Answer: Experimental results involving pigmentation in wheat
showed that a number of additive alleles acting in Mendelian fashion
could explain continuous variation.
◉ How do we assess environmental factors to determine if they
impact the phenotype of a quantitatively inherited trait?.
Answer: by heritability estimation
AND DETAILED SOLUTIONS
◉ When multiple genes contribute to the expression of a phenotype
they are called ________.
Answer: additive alleles
◉ How many gene pairs are involved in generating a typical
1:4:6:4:1 ratio.
Answer: 2
◉ Bell-shaped distributions produced by plotting results of F2 and
F3 crosses are typical of which type of inheritance.
Answer: multiple-factor inheritance
◉ To estimate how much the means of a variety of like samples
drawn from the same population might vary, what statistic is often
used?.
Answer: standard deviation of the mean
◉ Define the term broad-sense heritability (H2)..
Answer: Broad-sense heritability (H2 ) refers to the degree to which
phenotypic variation is due to genetic factors.
,◉ What is implied by a relatively high value of H2?.
Answer: A very high value of H2 indicates that the environment had
a relatively low impact on genotypic variation.
◉ Choose aspects of broad-sense heritability in equation form..
Answer: VP = VE + VG + VGE
◉ Interpret the meaning of an H2 (broad-sense heritability) value
that approaches 1.0..
Answer: Almost all the phenotypic variation is determined by
environmental factors.
◉ What is the name of the process of selecting a specific group of
organisms from an initially heterogeneous population for future
breeding purposes?.
Answer: artificial selection
◉ Expression QTL mapping allows researchers to characterize
________..
Answer: loci that control gene expression
◉ How do we know that threshold traits are actually polygenic even
though they may have as few as two discrete phenotypic classes?.
, Answer: -Polygenic conditions involving thresholds occur if a range
of expression is possible, but the trait is either expressed or not
expressed.
-Environmental factors have a considerable impact on polygenic
system, and therefore, on expression of threshold traits.
Submit
◉ How can we ascertain the number of polygenes involved in the
inheritance of a quantitative trait?.
Answer: -1/4^n, where n=the number of polygenes if the ratio of F2
individuals resembling either of the two extreme P1 phenotypes can
be determined
-(2n+1), where (2n+1) is the number of possible phenotypes and n
equals the number of additive loci
◉ What findings led geneticists to postulate the multiple-factor
hypothesis that invoked the idea of additive alleles to explain
inheritance patterns?.
Answer: Experimental results involving pigmentation in wheat
showed that a number of additive alleles acting in Mendelian fashion
could explain continuous variation.
◉ How do we assess environmental factors to determine if they
impact the phenotype of a quantitatively inherited trait?.
Answer: by heritability estimation
