GENETICS EXAM 3 COMPLETE COURSE
REVIEW GUIDE
◉ 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
◉ How do we know that monozygotic twins are not identical
genotypically as adults?.
Answer: differences in inherited disease states
◉ ______________ cures individuals with defective alleles and thus
__________ the likelihood that less fit alleles will enter and be
maintained in the gene poo.
Answer: Somatic gene therapy, increases
◉ __________________ could lead to removal of the defective allele from
a gene lineage; its impact on the course of human evolution will be
___________..
Answer: Germ-line therapy, negligible
◉ Are there nucleotide substitutions that will not be detected by
electrophoretic studies of a gene's protein product?.
REVIEW GUIDE
◉ 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
◉ How do we know that monozygotic twins are not identical
genotypically as adults?.
Answer: differences in inherited disease states
◉ ______________ cures individuals with defective alleles and thus
__________ the likelihood that less fit alleles will enter and be
maintained in the gene poo.
Answer: Somatic gene therapy, increases
◉ __________________ could lead to removal of the defective allele from
a gene lineage; its impact on the course of human evolution will be
___________..
Answer: Germ-line therapy, negligible
◉ Are there nucleotide substitutions that will not be detected by
electrophoretic studies of a gene's protein product?.
