GENETICS FINAL EXAM
QUESTIONS AND THEIR EXPECTED
ANSWERS
Expected Phenotype ratio of dihybrid cross
9:3:3:1
Flower color in a plant you are studying is produced
through a series of enzymatic reactions. In one step,
controlled by the P locus, a yellow pigment is altered
to be pink. There is a recessive p allele at that locus
and the yellow-to-pink alteration is not made.
Individuals with the pp genotype have yellow flowers.
In the next step, controlled by the R locus, the
dominant trait modifies the pink pigment to be a deep
red.
If you perform a PpRr x PpRr dihybrid cross, what do
you expect the offspring phenotype ratio to be for
red:pink:yellow flowers?
9:3:4
A common form of human color-blindness is X-linked,
with the color-blind trait being recessive. Which of the
following must be true, if a woman has a color-blind
daughter?
If the color-blind daughter has any sisters, they will all
also be color-blind
,The woman (the mother) must be color-blind
The father must be color-blind
If this color-blind daughter has any brothers, they will
all also be color-blind
Father
What is the cellular mechanism that causes alleles to
segregate into different gametes during meiosis?
anaphase 1
Does epistasis with two genes create more or less
phenotypes than a typical two gene cross
fewer
A species of plant shows incomplete dominance for
flower color, with Orange (COCO), Yellow (COCW) and
White (CWCW) flowers. You cross an orange-flowered
plant to a white-flowered plant, and get 58 offspring.
How many of those 58 offspring are expected to have
yellow flowers?
29
In Mendel's peas, tall (T) is dominant to short (t), and
purple flowers (P) are dominant to white flowers (p).
You cross a tall, purple-flowered plant to a short,
white-flowered plant and obtain 24 tall, purple-
flowered and 21 tall, white-flowered offspring. Which
of the following is true?
The cross a testcross for the P gene but not for the T
gene
, The cross was TtPP x ttpp
The cross was TtPp x ttpp
The cross was TTPp x ttpp
TTPp x ttpp
For rare traits, what can we assume about individuals
who marry into the pedigree?
homozygous unaffected
An individual has the genotype AaBBCcDd. What is
the probability that any one gamete produced by the
individual will have the genotype aBcD?
.125
At which stage of Meiosis does DNA replication
occur?
before prophase 1
Drosophila melanogaster (the fruit fly) is a popular
model organism for genetics. One of the primary
contributing factors that make Drosophila so popular
is that they
have short generation times
What is the indicator of an autosomal recessive trait in
a pedigree
Two unaffected parents have at least one affected
offspring
FoxP2 is located on human Chromosome 7 and all
together spans about 300,000 base pairs. Most people
are
heterozygous at over 100 of those 300,000 base pairs.
A valid definition of epistasis is that
the genotype at one locus can be changed by the
QUESTIONS AND THEIR EXPECTED
ANSWERS
Expected Phenotype ratio of dihybrid cross
9:3:3:1
Flower color in a plant you are studying is produced
through a series of enzymatic reactions. In one step,
controlled by the P locus, a yellow pigment is altered
to be pink. There is a recessive p allele at that locus
and the yellow-to-pink alteration is not made.
Individuals with the pp genotype have yellow flowers.
In the next step, controlled by the R locus, the
dominant trait modifies the pink pigment to be a deep
red.
If you perform a PpRr x PpRr dihybrid cross, what do
you expect the offspring phenotype ratio to be for
red:pink:yellow flowers?
9:3:4
A common form of human color-blindness is X-linked,
with the color-blind trait being recessive. Which of the
following must be true, if a woman has a color-blind
daughter?
If the color-blind daughter has any sisters, they will all
also be color-blind
,The woman (the mother) must be color-blind
The father must be color-blind
If this color-blind daughter has any brothers, they will
all also be color-blind
Father
What is the cellular mechanism that causes alleles to
segregate into different gametes during meiosis?
anaphase 1
Does epistasis with two genes create more or less
phenotypes than a typical two gene cross
fewer
A species of plant shows incomplete dominance for
flower color, with Orange (COCO), Yellow (COCW) and
White (CWCW) flowers. You cross an orange-flowered
plant to a white-flowered plant, and get 58 offspring.
How many of those 58 offspring are expected to have
yellow flowers?
29
In Mendel's peas, tall (T) is dominant to short (t), and
purple flowers (P) are dominant to white flowers (p).
You cross a tall, purple-flowered plant to a short,
white-flowered plant and obtain 24 tall, purple-
flowered and 21 tall, white-flowered offspring. Which
of the following is true?
The cross a testcross for the P gene but not for the T
gene
, The cross was TtPP x ttpp
The cross was TtPp x ttpp
The cross was TTPp x ttpp
TTPp x ttpp
For rare traits, what can we assume about individuals
who marry into the pedigree?
homozygous unaffected
An individual has the genotype AaBBCcDd. What is
the probability that any one gamete produced by the
individual will have the genotype aBcD?
.125
At which stage of Meiosis does DNA replication
occur?
before prophase 1
Drosophila melanogaster (the fruit fly) is a popular
model organism for genetics. One of the primary
contributing factors that make Drosophila so popular
is that they
have short generation times
What is the indicator of an autosomal recessive trait in
a pedigree
Two unaffected parents have at least one affected
offspring
FoxP2 is located on human Chromosome 7 and all
together spans about 300,000 base pairs. Most people
are
heterozygous at over 100 of those 300,000 base pairs.
A valid definition of epistasis is that
the genotype at one locus can be changed by the
