BIO325 Exam Study Questions with Verified
Correct Answers
QUIZ 1
If an Ss x Ss mating is performed and the progeny have the following phenotypic ratios of 3 S_
, (- indicates that the other allele is unknown) and 1 ss, what is the dominance relationship?
the S allele is dominant to the s allele
In some genetically engineered corn plants, a Bt gene was added to a chromosome. The Bt
gene specifies a protein called Bt that is lethal to certain flying insect pests that eat the corn
plants. If the corn plant is heterozygous for the Bt gene (one homolog has the introduced Bt
gene and the other does not), what proportion of the sperm would carry the Bt gene? And is
the presence of the Bt gene (a mutation) dominant or recessive to its absence (the wild type)
if the hybrid makes the Bt protein?
1/2; dominant
If you toss a coin twice and get two heads, what is the probability that you will get two tails
on the next two coin tosses?
1/4
In corn, having ligules (L) is dominant to liguleless (l), and green leaves (G) is dominant to
white leaves (g).
If a pure-breeding plant that is liguleless and has green leaves is crossed to a pure-breeding
plant with ligules and white leaves, predict the genotype and phenotype of the F1.
LlGg; green and ligules
Which of the following probabilities is correct regarding a mating of an Ss RR individual to an
individual who is Ss Rr ? ( - indicates the the second allele is either dominant or recessive.)
Heterozygous both alleles: 50% or 1/2
S- RR: 75% or 3/4
Homozygous recessive: 10% or 1/10
ss R- : 25% or 1/4
ss R- : 25% or 1/4
,In corn, having ligules (L) is dominant to liguleless (l), and green leaves (G) is dominant to
white leaves (g).
If a pure-breeding liguleless plant with green leaves is crossed to pure-breeding plant with
ligules and white leaves to produce F1 progeny, predict the proportion of F2 progeny with the
genotype Ll gg.
1/8
Why do scientists think that all forms of life on earth have a common origin?
-Related genes from different organisms have similar nucleotide sequences
-All living organisms use the same genetic code
-Related genes from different organisms have similar amino acid sequences
-Different organisms have related genes with similar functions
If an individual has 10 gene pairs, how many different gametes can be formed if six of the
gene pairs are homozygous and the remaining four gene pairs are heterozygous?
16
Sickle cell anemia is a recessive disease in humans. In a cross between a father who has sickle
cell anemia and a mother who is a carrier of the sickle cell allele, what is the probability that
all of their first four children will have the disease?
1/2
QUIZ 2
Which ratio would indicate that a phenotype is controlled by more than one gene?
3:1
9:3:3:1
2:1
1:2:1
9:3:3:1
Fruit flies with one allele for curly wings (Cy) and one allele for normal wings (Cy+) have curly
wings. Fruit flies with two copies of the Cy allele are never born.
What is the ratio of curly flies to normal flies when two curly-winged flies are crossed? (Note
that only live progeny are considered)
1 normal: 2 curly
, Two alleles of gene C control hair color in horses: C¹ and C². Horses homozygous for C¹ allele
are red, heterozygotes are yellow, and C² homozygotes are cream. In the offspring of mating
between heterozygotes, what phenotypic ratio is expected?
1 red: 2 yellow: 1 cream
Below is a pedigree for a common human trait (not a disease) controlled by a single gene that
has two different alleles A or a. Shaded symbols are for individuals exhibiting the trait.
Identify the mode of inheritance of the trait.
Recessive
Types of allele interactions of a single gene
-multiple alleles (polymorphism)
- incomplete dominance
-complete dominance
-codominance
Below is a pedigree for a common human trait (not a disease) controlled by a single gene that
has two different alleles A or a. Shaded symbols are for individuals exhibiting the trait.
If individuals 4 and 7 have a child, what is the probability that the child will exhibit the trait?
1/6
Fruit flies with one allele for curly wings (Cy) and one allele for normal wings (Cy+) have curly
wings. Fruit flies with two copies of the Cy allele are never born.
What is the dominant allele in terms of viability and wing phenotype?
The Cy+ allele is dominant for viability; the Cy allele is dominant for wing phenotype.
Below is a pedigree for a common human trait (not a disease) controlled by a single gene that
has two different alleles A or a. Shaded symbols are for individuals exhibiting the trait.
What is/are the possible genotype(s) of person 5?
Aa
Which parents could produce a girl with blood type A?
-AB and B
-A and B
Correct Answers
QUIZ 1
If an Ss x Ss mating is performed and the progeny have the following phenotypic ratios of 3 S_
, (- indicates that the other allele is unknown) and 1 ss, what is the dominance relationship?
the S allele is dominant to the s allele
In some genetically engineered corn plants, a Bt gene was added to a chromosome. The Bt
gene specifies a protein called Bt that is lethal to certain flying insect pests that eat the corn
plants. If the corn plant is heterozygous for the Bt gene (one homolog has the introduced Bt
gene and the other does not), what proportion of the sperm would carry the Bt gene? And is
the presence of the Bt gene (a mutation) dominant or recessive to its absence (the wild type)
if the hybrid makes the Bt protein?
1/2; dominant
If you toss a coin twice and get two heads, what is the probability that you will get two tails
on the next two coin tosses?
1/4
In corn, having ligules (L) is dominant to liguleless (l), and green leaves (G) is dominant to
white leaves (g).
If a pure-breeding plant that is liguleless and has green leaves is crossed to a pure-breeding
plant with ligules and white leaves, predict the genotype and phenotype of the F1.
LlGg; green and ligules
Which of the following probabilities is correct regarding a mating of an Ss RR individual to an
individual who is Ss Rr ? ( - indicates the the second allele is either dominant or recessive.)
Heterozygous both alleles: 50% or 1/2
S- RR: 75% or 3/4
Homozygous recessive: 10% or 1/10
ss R- : 25% or 1/4
ss R- : 25% or 1/4
,In corn, having ligules (L) is dominant to liguleless (l), and green leaves (G) is dominant to
white leaves (g).
If a pure-breeding liguleless plant with green leaves is crossed to pure-breeding plant with
ligules and white leaves to produce F1 progeny, predict the proportion of F2 progeny with the
genotype Ll gg.
1/8
Why do scientists think that all forms of life on earth have a common origin?
-Related genes from different organisms have similar nucleotide sequences
-All living organisms use the same genetic code
-Related genes from different organisms have similar amino acid sequences
-Different organisms have related genes with similar functions
If an individual has 10 gene pairs, how many different gametes can be formed if six of the
gene pairs are homozygous and the remaining four gene pairs are heterozygous?
16
Sickle cell anemia is a recessive disease in humans. In a cross between a father who has sickle
cell anemia and a mother who is a carrier of the sickle cell allele, what is the probability that
all of their first four children will have the disease?
1/2
QUIZ 2
Which ratio would indicate that a phenotype is controlled by more than one gene?
3:1
9:3:3:1
2:1
1:2:1
9:3:3:1
Fruit flies with one allele for curly wings (Cy) and one allele for normal wings (Cy+) have curly
wings. Fruit flies with two copies of the Cy allele are never born.
What is the ratio of curly flies to normal flies when two curly-winged flies are crossed? (Note
that only live progeny are considered)
1 normal: 2 curly
, Two alleles of gene C control hair color in horses: C¹ and C². Horses homozygous for C¹ allele
are red, heterozygotes are yellow, and C² homozygotes are cream. In the offspring of mating
between heterozygotes, what phenotypic ratio is expected?
1 red: 2 yellow: 1 cream
Below is a pedigree for a common human trait (not a disease) controlled by a single gene that
has two different alleles A or a. Shaded symbols are for individuals exhibiting the trait.
Identify the mode of inheritance of the trait.
Recessive
Types of allele interactions of a single gene
-multiple alleles (polymorphism)
- incomplete dominance
-complete dominance
-codominance
Below is a pedigree for a common human trait (not a disease) controlled by a single gene that
has two different alleles A or a. Shaded symbols are for individuals exhibiting the trait.
If individuals 4 and 7 have a child, what is the probability that the child will exhibit the trait?
1/6
Fruit flies with one allele for curly wings (Cy) and one allele for normal wings (Cy+) have curly
wings. Fruit flies with two copies of the Cy allele are never born.
What is the dominant allele in terms of viability and wing phenotype?
The Cy+ allele is dominant for viability; the Cy allele is dominant for wing phenotype.
Below is a pedigree for a common human trait (not a disease) controlled by a single gene that
has two different alleles A or a. Shaded symbols are for individuals exhibiting the trait.
What is/are the possible genotype(s) of person 5?
Aa
Which parents could produce a girl with blood type A?
-AB and B
-A and B
