ASU BIO 340 EXAM SCRIPT 2026
QUESTIONS WITH ANSWERS GRADED A+
●● Hypomorphic mutations. Answer: Genes that have lost only some of
their function
●● Null mutations. Answer: Genes that have lost all of their function
●● Haplo-sufficient. Answer: One (haplo) copy is sufficient to produce
the wild-type phenotype in the heterozygous genotype
●● Fully dominant mutations. Answer: Phenotype of a fully dominant
mutation is seen in both heterozygous and homozygous dominant
individuals.
●● Gain-of-function. Answer: gene product acquires a new function or
express increased wild type activity
●● Loss-of-function. Answer: there is a significant decrease or complete
loss of functional gene product
●● Incomplete dominance. Answer: phenotype of the heterozygote is
intermediate between the phenotypes of the two homozygotes on some
quantitative scale (color, size, etc)
,●● Codominance. Answer: Phenotypes of both alleles are fully
expressed in the heterozygote and leads to a different phenotype than
either homozygotes.
●● Allelic series of the C gene. Answer: Wild type allele: C, produces
full coat color
c^ch: produces a dilute phenotype, chinchilla
c^h: produces phenotype called Himalayan with little pigment on the
body but full color on the extremities (non functional at higher body
temps).
c:Fully recessive, null allele and produces an albino phenotype
●● complementation tests. Answer: Determine if mutations that cause
the same phenotype are in the same or different genes.
●● Epistatic interactions. Answer: when 2 or more genes affect the same
phenotype by influencing a common pathway.
●● Epistatic gene interaction ratios. Answer: None 9:3:3:1
Complementary 9:7
Duplicate 15:1
Dominant 9:6:1
Recessive epistatic 9:3:4
, Dominant epistasis 12:3:1
Dominant suppression 13:3
●● Duplicate gene interaction. Answer: (15:1)Genes that encode the
same product or products that have the same effect in a pathway. Ex: P
or R produce purple flowers but pr produces white.
●● Dominant Gene interaction. Answer: (9:6:1)Organisms that have A
and B will have a specific phenotype, organisms with A or B will have a
different phenotype and organisms with homozygous recessive will have
neither.
●● Recessive Epistasis. Answer: (9:3:4) B and E produce black, just E
produces brown, just B will produce golden and bbee will also produce
golden. B for black is not expressed unless E is present.
●● Dominant Epistasis. Answer: (12:3:1) In dominant epistasis a
dominant allele of one gene masks or reduces the expression of either
allele of the other gene. Ex: W_Y_: white, W_yy: white, wwY_: yellow,
wwyy: green A Dominant W masks dominant Y
●● Dominant suppression. Answer: Occurs when the dominant allele of
one gene suppresses the expression of a dominant allele of a 2nd gene.
Ex: C_I_: white, C_ii: colored, ccI_: white, ccii: white
when I is present it's white.
QUESTIONS WITH ANSWERS GRADED A+
●● Hypomorphic mutations. Answer: Genes that have lost only some of
their function
●● Null mutations. Answer: Genes that have lost all of their function
●● Haplo-sufficient. Answer: One (haplo) copy is sufficient to produce
the wild-type phenotype in the heterozygous genotype
●● Fully dominant mutations. Answer: Phenotype of a fully dominant
mutation is seen in both heterozygous and homozygous dominant
individuals.
●● Gain-of-function. Answer: gene product acquires a new function or
express increased wild type activity
●● Loss-of-function. Answer: there is a significant decrease or complete
loss of functional gene product
●● Incomplete dominance. Answer: phenotype of the heterozygote is
intermediate between the phenotypes of the two homozygotes on some
quantitative scale (color, size, etc)
,●● Codominance. Answer: Phenotypes of both alleles are fully
expressed in the heterozygote and leads to a different phenotype than
either homozygotes.
●● Allelic series of the C gene. Answer: Wild type allele: C, produces
full coat color
c^ch: produces a dilute phenotype, chinchilla
c^h: produces phenotype called Himalayan with little pigment on the
body but full color on the extremities (non functional at higher body
temps).
c:Fully recessive, null allele and produces an albino phenotype
●● complementation tests. Answer: Determine if mutations that cause
the same phenotype are in the same or different genes.
●● Epistatic interactions. Answer: when 2 or more genes affect the same
phenotype by influencing a common pathway.
●● Epistatic gene interaction ratios. Answer: None 9:3:3:1
Complementary 9:7
Duplicate 15:1
Dominant 9:6:1
Recessive epistatic 9:3:4
, Dominant epistasis 12:3:1
Dominant suppression 13:3
●● Duplicate gene interaction. Answer: (15:1)Genes that encode the
same product or products that have the same effect in a pathway. Ex: P
or R produce purple flowers but pr produces white.
●● Dominant Gene interaction. Answer: (9:6:1)Organisms that have A
and B will have a specific phenotype, organisms with A or B will have a
different phenotype and organisms with homozygous recessive will have
neither.
●● Recessive Epistasis. Answer: (9:3:4) B and E produce black, just E
produces brown, just B will produce golden and bbee will also produce
golden. B for black is not expressed unless E is present.
●● Dominant Epistasis. Answer: (12:3:1) In dominant epistasis a
dominant allele of one gene masks or reduces the expression of either
allele of the other gene. Ex: W_Y_: white, W_yy: white, wwY_: yellow,
wwyy: green A Dominant W masks dominant Y
●● Dominant suppression. Answer: Occurs when the dominant allele of
one gene suppresses the expression of a dominant allele of a 2nd gene.
Ex: C_I_: white, C_ii: colored, ccI_: white, ccii: white
when I is present it's white.
