gcd 3022 exam 2 questions with complete solutions
3. Let's suppose an organism has a G + C content of 64% in its
DNA. What are the percentages of A, T, G, and C? Correct
Answers Answer:G = 32%, C = 32%, A = 18%, T = 18%.
A cross is made between a green four-o'clock and a white four
o'clock. Green chlorophyll synthesis is inherited via the
chloroplasts, which are maternally inherited in this species. If
the white plant provides the pollen, the expected outcome of the
offspring would be Correct Answers all plants with green
leaves
A gene in Drosophila called Bicoid exhibits a maternal effect
pattern. A Drosophila embryo is unable to survive due to a
recessive maternal effect allele designated bicoid-. The wild-
type allele is designated bicoid+. What are the genotypes and
phenotypes of the embryo's mother and maternal grandparents?
Correct Answers The genotype of the mother must be bic-bic-.
That is why the mother produces abnormal offspring. Because
the mother is alive and able to produce offspring, her mother
(the maternal grandmother) must have been bic+bic- and passed
the bic- allele to the daughter (the mother in this problem). The
maternal grandfather also must have passed the bic- allele to his
daughter. The maternal grandfather could be either bic+bic-or
bic-bic-.
A maternal effect pattern of inheritance can be explained by
Correct Answers nurse cells that provide the oocytes with gene
products
,A normal corn plant is diploid and carries 10 chromosomes per
set. If you assume that the following changes in chromosome
number are viable (i.e., can survive), which would you expect to
be the most fertile and have a phenotype that is not detrimental?
Correct Answers tetraploid
A person inherits an extra copy of chromosome 21 from their
mother. This is most likely due to Correct Answers
nondisjunction during meiosis.
A person with Down syndrome is Correct Answers aneuploid
A rare condition known as uniparental disomy happens when an
individual inherits both copies of a chromosome from one parent
and no copies from the other parent. For example, a sperm with
two copies of chromosome 15 could fertilize an egg with no
copies. This is known as paternal uniparental disomy 15. If a
female is born with paternal uniparental disomy 15, would you
expect her to be phenotypically normal, have Angelman
syndrome (AS), or have Prader-Willi syndrome (PWS)?
Explain. Would she produce normal offspring or offspring
affected with AS or PWS? Correct Answers A person born
with paternal uniparental disomy 15 would have Angelman
syndrome, because this individual would not have an active
copy of the AS gene; the paternally inherited copies of the AS
gene are silenced. This individual would have normal offspring,
because she does not have a deletion in either copy of
chromosome 15.
A researcher conducted crosses between two different strains of
Drosophila. When true-breeding flies with singed bristles (s) and
, normal wings (L) were crossed to true-breeding flies with
normal bristles (S) and vestigial wings (l), all F1 offspring had
normal wings and normal bristles. The F1 offspring were
crossed to flies with singed bristles and vestigial wings. Which
F2 offspring is/are recombinant? Correct Answers Singed
bristles/vestigial wings and normal bristles/normal wings
acrocentric chromosome Correct Answers Chromosome in
which the centromere is near one end, producing a long arm at
one end and a knob, or satellite, at the other end.
After a gene duplication occurs, the resulting genes will
accumulate different mutations, thereby causing them to have
somewhat different DNA sequences. Take a look at Figure 8.7.
Which gene pair would be expected to have greater sequence
similarity? Would it be α1 and α2 or ψα1 and α2? Explain your
reasoning. Correct Answers You would expect α1 and α2 to be
more similar, because they have diverged more recently.
Therefore, there has been less time for them to accumulate
random mutations that would mke their sequences different
Also be able to predict the outcome of a cross if you already
know the map distance between two genes. Correct Answers
An individual with a reciprocal translocation usually exhibits an
external phenotype that seems to be normal. Even so, explain
why such an individual may have a high probability of
producing offspring with abnormal phenotypes? Correct
Answers An individual with a reciprocal translocation has a
normal amount of genetic material. Therefore, if a breakpoint is
not within a vital gene and if there are no position effects, the
3. Let's suppose an organism has a G + C content of 64% in its
DNA. What are the percentages of A, T, G, and C? Correct
Answers Answer:G = 32%, C = 32%, A = 18%, T = 18%.
A cross is made between a green four-o'clock and a white four
o'clock. Green chlorophyll synthesis is inherited via the
chloroplasts, which are maternally inherited in this species. If
the white plant provides the pollen, the expected outcome of the
offspring would be Correct Answers all plants with green
leaves
A gene in Drosophila called Bicoid exhibits a maternal effect
pattern. A Drosophila embryo is unable to survive due to a
recessive maternal effect allele designated bicoid-. The wild-
type allele is designated bicoid+. What are the genotypes and
phenotypes of the embryo's mother and maternal grandparents?
Correct Answers The genotype of the mother must be bic-bic-.
That is why the mother produces abnormal offspring. Because
the mother is alive and able to produce offspring, her mother
(the maternal grandmother) must have been bic+bic- and passed
the bic- allele to the daughter (the mother in this problem). The
maternal grandfather also must have passed the bic- allele to his
daughter. The maternal grandfather could be either bic+bic-or
bic-bic-.
A maternal effect pattern of inheritance can be explained by
Correct Answers nurse cells that provide the oocytes with gene
products
,A normal corn plant is diploid and carries 10 chromosomes per
set. If you assume that the following changes in chromosome
number are viable (i.e., can survive), which would you expect to
be the most fertile and have a phenotype that is not detrimental?
Correct Answers tetraploid
A person inherits an extra copy of chromosome 21 from their
mother. This is most likely due to Correct Answers
nondisjunction during meiosis.
A person with Down syndrome is Correct Answers aneuploid
A rare condition known as uniparental disomy happens when an
individual inherits both copies of a chromosome from one parent
and no copies from the other parent. For example, a sperm with
two copies of chromosome 15 could fertilize an egg with no
copies. This is known as paternal uniparental disomy 15. If a
female is born with paternal uniparental disomy 15, would you
expect her to be phenotypically normal, have Angelman
syndrome (AS), or have Prader-Willi syndrome (PWS)?
Explain. Would she produce normal offspring or offspring
affected with AS or PWS? Correct Answers A person born
with paternal uniparental disomy 15 would have Angelman
syndrome, because this individual would not have an active
copy of the AS gene; the paternally inherited copies of the AS
gene are silenced. This individual would have normal offspring,
because she does not have a deletion in either copy of
chromosome 15.
A researcher conducted crosses between two different strains of
Drosophila. When true-breeding flies with singed bristles (s) and
, normal wings (L) were crossed to true-breeding flies with
normal bristles (S) and vestigial wings (l), all F1 offspring had
normal wings and normal bristles. The F1 offspring were
crossed to flies with singed bristles and vestigial wings. Which
F2 offspring is/are recombinant? Correct Answers Singed
bristles/vestigial wings and normal bristles/normal wings
acrocentric chromosome Correct Answers Chromosome in
which the centromere is near one end, producing a long arm at
one end and a knob, or satellite, at the other end.
After a gene duplication occurs, the resulting genes will
accumulate different mutations, thereby causing them to have
somewhat different DNA sequences. Take a look at Figure 8.7.
Which gene pair would be expected to have greater sequence
similarity? Would it be α1 and α2 or ψα1 and α2? Explain your
reasoning. Correct Answers You would expect α1 and α2 to be
more similar, because they have diverged more recently.
Therefore, there has been less time for them to accumulate
random mutations that would mke their sequences different
Also be able to predict the outcome of a cross if you already
know the map distance between two genes. Correct Answers
An individual with a reciprocal translocation usually exhibits an
external phenotype that seems to be normal. Even so, explain
why such an individual may have a high probability of
producing offspring with abnormal phenotypes? Correct
Answers An individual with a reciprocal translocation has a
normal amount of genetic material. Therefore, if a breakpoint is
not within a vital gene and if there are no position effects, the
