Genetic Exam questions and
answers graded A+
If a 40 base single stranded piece of DNA contains 22 T bases, how many G bases does the
corresponding single-stranded DNA contain?
A) Not enough information
B) 9
C) 18
D) 22
E) 36 - ANS✅✅A) Not enough information
You have no way of knowing how many G bases are on the complementary strand. You only know
that the total number of G and C bases combined on the complementary strand equals 18.
If a 35 base pair double stranded piece of DNA contains 11 C bases, how many T bases does it
contain?
Hint: A drawing will help - ANS✅✅24
The two DNA strands of a chromosome are held together by: (What keeps the 2 single strands
together to form a double strand?) Choose all correct answers.
A) the centromere
B) covalent bonds
C) base complementarity
D) DNA backbone
E) hydrogen bonds
F) DNA polymerase - ANS✅✅C) base complementarity
E) hydrogen bonds
,Analysis of the bases of a sample of nucleic acid yielded these percentages: A, 20%; G, 30%; C, 20%;
T, 30%. The sample could be... Choose all correct answers.
A) single-stranded DNA.
B) double-stranded RNA.
C) double-stranded DNA.
D) single-stranded RNA. - ANS✅✅A) single-stranded DNA.
Which of the following is not true about a linear molecule of double-stranded DNA?
A) Pentose sugars are linked via covalent phosphodiester bonds.
B) At one end, two 5' phosphate groups can be found.
C) Bases are paired via hydrogen bonds.
D) It is a double helix composed of antiparallel strands. - ANS✅✅B) At one end, two 5' phosphate
groups can be found.
In the Hershey-Chase experiment, T2 phage were radioactively labeled with either 35S or 32P, and
allowed to infect E. coli. What results proved that DNA was the genetic material?
A) The 32P was found in both progeny phage and in phage ghosts.
B) The 35S was found in both progeny phage and in phage ghosts.
C) The 35S was found in phage ghosts, and the 32P was found in progeny phage.
D) The 35S was found in progeny phage, and the 32P was found in phage ghosts. - ANS✅✅C) The
35S was found in phage ghosts, and the 32P was found in progeny phage.
Which of the following clusters of terms accurately describes DNA as it is generally viewed to exist in
prokaryotes and eukaryotes?
A) double-stranded, parallel, (A + T)/C + G) = 1.0, (A + G)/(C + T) = 1.0
B) double-stranded, parallel, (A + T)/C + G) = variable, (A + G)/(C + T) = 1.
C) double-stranded, antiparallel, (A + T)/C + G) = variable, (A + G)/(C + T) = variable
D) single-stranded, antiparallel, (A + T)/C + G) = 1.0, (A + G)/(C + T) = 1.0
,E) double-stranded, antiparallel, (A + T)/C + G) = variable, (A + G)/(C+ T) = 1.0 - ANS✅✅E) double-
stranded, antiparallel, (A + T)/C + G) = variable, (A + G)/(C+ T) = 1.0
DNA molecules of different sizes are often separated wit the use of a technique called
electrophoresis. With this technique, DNA molecules are placed in a gel, and he DNA molecules
migrate toward the + pole of the current. What aspect of its structure causes a DNA molecule to
migrate toward the positive pole?
A) The Nitrogenous Bases
B) The double helix
C) The Hydrogen Bonds
D) DNA is positively charged
E) The phosphate backbone - ANS✅✅E) The phosphate backbone
Which of the following DNA molecules has the lowest melting temperature?
A) AAATTGCGCGCCCGA
B) GAATTCCAATGTATA
C) GGGAGCTCGGTTGCC
D) GCATCGATCGATACG
E) AGGGTGGCTTAACGG - ANS✅✅B) GAATTCCAATGTATA
Most AT content (least GC content)/less hydrogen bonds keeping the strands together
A diploid human cell contains approximately 6.4 billion base pairs of DNA.
How many histone proteins are complexed to this DNA? - ANS✅✅288,000,000
6.4 x 10^9 (bp) / 200 (bp/nucleosome) * 9 (histone/nucleosome)
How different is your Genome from your friends? Are most of these differences important in terms
of phenotypic expression? Why or why not? - ANS✅✅ANSWER: Our genomes are 99.9% identical
differing by 1 base in every 1000 bases. Most differences in our genomes have no bearing on our
, phenotype as the majority of the DNA does not code for genes. Of the small fraction of differences
that are located on genes, many of these still do not result in any noticeable phenotypic difference.
Describe how the definition of both phenotype and genotype has changed from its original meaning
back in the 1800s to what these terms mean in modern day genetics. - ANS✅✅ANSWER: The
original definition of phenotype referred to the physical, observable properties of an individual. The
genotype referred to the inferred cause of the phenotype termed "genes" at the time. We now
know that the genotype of an individual comes from the individuals genes located on their DNA.
Phenotypes now refer not only to the physical traits that can be seen, but also the molecules, which
are a result of gene expression and that ultimately factor into the observable traits (i.e. proteins).
Describe four major functions of DNA in a cell. - ANS✅✅ANSWER: replication = duplication of
genetic material; expression = production of a phenotype; storage = stable maintenance and passage
of information; variation = capable of alteration
Which of the following is a chemical or structural characteristic of RNA that is different from those of
DNA? (CHOOSE ALL THAT APPLY)
A) RNA molecules are generally shorter in length than those of DNA macromolecules.
B) The RNA sugar is ribose instead of deoxyribose.
C) RNA is usually a single-stranded molecule instead of a hydrogen-bonded double strand like DNA.
D) The bases in RNA include uracil instead of thymine. - ANS✅✅A) RNA molecules are generally
shorter in length than those of DNA macromolecules.
B) The RNA sugar is ribose instead of deoxyribose.
C) RNA is usually a single-stranded molecule instead of a hydrogen-bonded double strand like DNA.
D) The bases in RNA include uracil instead of thymine.
* ON LAPTOP
You are a researcher studying the genetic basis of colon cancer. You have been working with a colon
cancer cell line to determine the expression levels of different genes that might contribute to cancer
formation. You obtain the DNA methylation status of five genes of interest (the data is shown in the
table below). The plus (+) sign indicates the level of DNA methylation; more plus signs correlates
with increased methylation levels.
Based on the information shown above, which gene would you predict to have the highest rate of
transcription?
answers graded A+
If a 40 base single stranded piece of DNA contains 22 T bases, how many G bases does the
corresponding single-stranded DNA contain?
A) Not enough information
B) 9
C) 18
D) 22
E) 36 - ANS✅✅A) Not enough information
You have no way of knowing how many G bases are on the complementary strand. You only know
that the total number of G and C bases combined on the complementary strand equals 18.
If a 35 base pair double stranded piece of DNA contains 11 C bases, how many T bases does it
contain?
Hint: A drawing will help - ANS✅✅24
The two DNA strands of a chromosome are held together by: (What keeps the 2 single strands
together to form a double strand?) Choose all correct answers.
A) the centromere
B) covalent bonds
C) base complementarity
D) DNA backbone
E) hydrogen bonds
F) DNA polymerase - ANS✅✅C) base complementarity
E) hydrogen bonds
,Analysis of the bases of a sample of nucleic acid yielded these percentages: A, 20%; G, 30%; C, 20%;
T, 30%. The sample could be... Choose all correct answers.
A) single-stranded DNA.
B) double-stranded RNA.
C) double-stranded DNA.
D) single-stranded RNA. - ANS✅✅A) single-stranded DNA.
Which of the following is not true about a linear molecule of double-stranded DNA?
A) Pentose sugars are linked via covalent phosphodiester bonds.
B) At one end, two 5' phosphate groups can be found.
C) Bases are paired via hydrogen bonds.
D) It is a double helix composed of antiparallel strands. - ANS✅✅B) At one end, two 5' phosphate
groups can be found.
In the Hershey-Chase experiment, T2 phage were radioactively labeled with either 35S or 32P, and
allowed to infect E. coli. What results proved that DNA was the genetic material?
A) The 32P was found in both progeny phage and in phage ghosts.
B) The 35S was found in both progeny phage and in phage ghosts.
C) The 35S was found in phage ghosts, and the 32P was found in progeny phage.
D) The 35S was found in progeny phage, and the 32P was found in phage ghosts. - ANS✅✅C) The
35S was found in phage ghosts, and the 32P was found in progeny phage.
Which of the following clusters of terms accurately describes DNA as it is generally viewed to exist in
prokaryotes and eukaryotes?
A) double-stranded, parallel, (A + T)/C + G) = 1.0, (A + G)/(C + T) = 1.0
B) double-stranded, parallel, (A + T)/C + G) = variable, (A + G)/(C + T) = 1.
C) double-stranded, antiparallel, (A + T)/C + G) = variable, (A + G)/(C + T) = variable
D) single-stranded, antiparallel, (A + T)/C + G) = 1.0, (A + G)/(C + T) = 1.0
,E) double-stranded, antiparallel, (A + T)/C + G) = variable, (A + G)/(C+ T) = 1.0 - ANS✅✅E) double-
stranded, antiparallel, (A + T)/C + G) = variable, (A + G)/(C+ T) = 1.0
DNA molecules of different sizes are often separated wit the use of a technique called
electrophoresis. With this technique, DNA molecules are placed in a gel, and he DNA molecules
migrate toward the + pole of the current. What aspect of its structure causes a DNA molecule to
migrate toward the positive pole?
A) The Nitrogenous Bases
B) The double helix
C) The Hydrogen Bonds
D) DNA is positively charged
E) The phosphate backbone - ANS✅✅E) The phosphate backbone
Which of the following DNA molecules has the lowest melting temperature?
A) AAATTGCGCGCCCGA
B) GAATTCCAATGTATA
C) GGGAGCTCGGTTGCC
D) GCATCGATCGATACG
E) AGGGTGGCTTAACGG - ANS✅✅B) GAATTCCAATGTATA
Most AT content (least GC content)/less hydrogen bonds keeping the strands together
A diploid human cell contains approximately 6.4 billion base pairs of DNA.
How many histone proteins are complexed to this DNA? - ANS✅✅288,000,000
6.4 x 10^9 (bp) / 200 (bp/nucleosome) * 9 (histone/nucleosome)
How different is your Genome from your friends? Are most of these differences important in terms
of phenotypic expression? Why or why not? - ANS✅✅ANSWER: Our genomes are 99.9% identical
differing by 1 base in every 1000 bases. Most differences in our genomes have no bearing on our
, phenotype as the majority of the DNA does not code for genes. Of the small fraction of differences
that are located on genes, many of these still do not result in any noticeable phenotypic difference.
Describe how the definition of both phenotype and genotype has changed from its original meaning
back in the 1800s to what these terms mean in modern day genetics. - ANS✅✅ANSWER: The
original definition of phenotype referred to the physical, observable properties of an individual. The
genotype referred to the inferred cause of the phenotype termed "genes" at the time. We now
know that the genotype of an individual comes from the individuals genes located on their DNA.
Phenotypes now refer not only to the physical traits that can be seen, but also the molecules, which
are a result of gene expression and that ultimately factor into the observable traits (i.e. proteins).
Describe four major functions of DNA in a cell. - ANS✅✅ANSWER: replication = duplication of
genetic material; expression = production of a phenotype; storage = stable maintenance and passage
of information; variation = capable of alteration
Which of the following is a chemical or structural characteristic of RNA that is different from those of
DNA? (CHOOSE ALL THAT APPLY)
A) RNA molecules are generally shorter in length than those of DNA macromolecules.
B) The RNA sugar is ribose instead of deoxyribose.
C) RNA is usually a single-stranded molecule instead of a hydrogen-bonded double strand like DNA.
D) The bases in RNA include uracil instead of thymine. - ANS✅✅A) RNA molecules are generally
shorter in length than those of DNA macromolecules.
B) The RNA sugar is ribose instead of deoxyribose.
C) RNA is usually a single-stranded molecule instead of a hydrogen-bonded double strand like DNA.
D) The bases in RNA include uracil instead of thymine.
* ON LAPTOP
You are a researcher studying the genetic basis of colon cancer. You have been working with a colon
cancer cell line to determine the expression levels of different genes that might contribute to cancer
formation. You obtain the DNA methylation status of five genes of interest (the data is shown in the
table below). The plus (+) sign indicates the level of DNA methylation; more plus signs correlates
with increased methylation levels.
Based on the information shown above, which gene would you predict to have the highest rate of
transcription?
