Genetics : Genetic Engineering

Study concepts, example questions & explanations for Genetics

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Example Questions

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Example Question #1 : Genetic Engineering

A diagram that depicts a human's genetic information with chromosome pairs is called a __________.

Possible Answers:

gene sequence

punnett square

pedigree

karyotype

Correct answer:

karyotype

Explanation:

A karyotype is a diagram that depicts all 23 pairs of chromosomes by showing their shapes relative to one another. The process of karyotyping involves examining chromosomes to identify any genetic problems that could result in a disorder or disease. 

Example Question #2 : Genetic Engineering

Which of the following methods of genetic engineering is capable of inserting DNA into a specific location of the host cell’s chromosomal DNA? 

Possible Answers:

Coating particles of gold or tungsten with DNA and shooting them into cells

Transformation using calcium chloride

Homologous recombination

Transformation using electroporation

DNA insertion using viral vectors

Correct answer:

Homologous recombination

Explanation:

Homologous recombination is a natural process in many organisms that cells use to repair DNA, increase genetic variation of offspring during meiosis, or to transfer DNA between individual in viruses or bacteria. In genetic engineering, a section of chromosomal DNA is replaced with a modified version of that segment. Since specific sequences of DNA are being replaced rather than just inserted between natural occurring sequences, this method allows DNA to be placed in specific location in the cell’s chromosomal DNA.

Example Question #3 : Genetic Engineering

Viruses can be modified to be used as vectors in genetic engineering. Which characteristic(s) of viral vectors limits their usefulness for gene therapy in humans?

I. The vector replicates rapidly in targeted cells, damaging the cell.

II. Viral vectors have low efficiency at introducing DNA to cells when compared with transformation.

III. Viruses often randomly insert genes into the host chromosome, potentially disrupting gene functions and causing cancer in the host.

IV. The host’s own immune response to the viral vector can cause complications for the patient.

Possible Answers:

II and IV

II only

I and IV

III only

III and IV

Correct answer:

III and IV

Explanation:

Viral vectors are modified so that they can infect cells, but they cannot replicate. Viral vectors are also much more efficient at introducing DNA to cells than transformation. Even though the virus has been modified to be harmless, however, the host’s immune system can still attack it, leading to a potentially dangerous immune response. Many viruses randomly insert their DNA into host chromosomes, possibly inserting the DNA in the middle of a host gene and interrupting the gene’s function. If the affected host gene is important in cell replication, DNA repair, or programmed cell death, this could lead to cancer.

Example Question #4 : Genetic Engineering

What is the role of calcium chloride in making bacterial cells competent for transformation? 

Possible Answers:

It adds stability to the plasma membrane so that the cell can survive heat shock.

It causes pores to open in the plasmid membrane so that plasmid DNA may enter.

The calcium starts a signal relay that promotes expression of the plasmid genes.

It promotes the binding of plasmid DNA to the bacterial plasma membrane.

It interrupts bacterial defensive processes that would destroy DNA.

Correct answer:

It promotes the binding of plasmid DNA to the bacterial plasma membrane.

Explanation:

Positively charged calcium ions are attracted to both the negatively charged plasmid DNA and the negatively charged plasma membrane, overcoming the usual repulsion between the two and allowing them to bind. Heat shock is used to open pores during the transformation process, so that the bound plasmid DNA can enter the cell. Bacteria defenses generally destroy viral DNA, not bacterial plasmid DNA. Calcium is used as a signal in many cell processes, but this is not the purpose of calcium chloride in transformation. 

Example Question #5 : Genetic Engineering

A bacterial colony is transformed with a plasmid containing a foreign gene of interest and is then plated and incubated. The plasmid has been designed so that it will express both this gene and a gene that codes for a green fluorescent protein. The gene that expresses the fluorescent protein is known as what?

Possible Answers:

Reporter gene

Promoter gene

Double knockout gene

Gene knock-in

Knockout gene

Correct answer:

Reporter gene

Explanation:

A reporter gene is a gene that is introduced to cells along with a gene of interest in order to determine which cells have been successfully transformed. Since both genes are on the same plasmid, if the bacterial colonies after incubation fluoresce green then they also have the gene of interest, which may not be detected as easily. Knockout and knock-in genes refer to genetic changes chromosomal DNA and are not introduced using plasmids. A promoter refers to a part of a gene that regulates its expression.

Example Question #2 : Genetic Engineering

Scientists often introduce foreign genes from other organisms, including eukaryotes, into bacteria in order to mass-produce the gene product. What difference between bacteria and eukaryotes complicates this process?

Possible Answers:

Bacteria do not perform post-translational modification of proteins.

Bacteria do not perform post-transcriptional modification of mRNA.

Bacteria do perform post-translational modification of proteins.

Bacteria use different nitrogenous bases than eukaryotes.

Bacteria use different codons than eukaryotes to code for the same amino acid.

Correct answer:

Bacteria do not perform post-transcriptional modification of mRNA.

Explanation:

Bacteria do not perform post-transcriptional modification of mRNA. None of the other answers are actual differences between bacteria and eukaryotes. Bacteria begin translating mRNA into amino acids before transcription has even completed, giving them no opportunity to modify the mRNA transcript before translation. Therefore, a cDNA copy must be made from the already modified mRNA produced by the eukaryotic organism and then introduced into the bacterial cell. That way the bacteria can transcribe and translate the cDNA without having to modify the mRNA transcript.

Example Question #7 : Genetic Engineering

Which of the following is not generally introduced into a cell during genetic modification?

Possible Answers:

Ligase

Terminator

Vector

Selectable marker gene

Promoter

Correct answer:

Ligase

Explanation:

Vectors are used to deliver the target gene into the cell. The selectable marker gene, when expressed, shows that the genes were successfully introduced into the cell. A promoter is used to initiate transcription of both the target gene and the marker gene, and a terminator ends their transcription. While ligase is often used to make recombinant DNA to be inserted into a cell, it is not necessary to introduce ligase into the cell.

Example Question #8 : Genetic Engineering

If a blue zebra (genotype of Bb) mates with a pink zebra (genotype of bb), what will be the possible gametes of the blue zebra and what will be the possible gametes of the pink zebra?

Possible Answers:

blue zebra: B

pink zebra: b

blue zebra: B, b

pink zebra: b, b

blue zebra: b

pink zebra: b

blue zebra: Bb

pink zebra: bb

Correct answer:

blue zebra: B, b

pink zebra: b, b

Explanation:

Gametes contain half the genetic information as other cells in the body. If the genotype for the blue zebra is Bb, this means that half the genetic information for this phenotype of color would be a gamete containing B or a gamete containing b. Similarly, the possible gametes for the pink zebra with genotype bb would be b or b.

Example Question #3 : Genetic Engineering

If a green horse (genotype of Gg) mates with a yellow horse (genotype of gg), what will the phenotype and phenotypic ratio of the offspring be?

Possible Answers:

green : yellow

4 : 0

green : yellow

2 : 2

green : yellow

3 : 1

green : yellow

1 : 3

Correct answer:

green : yellow

2 : 2

Explanation:

In order to find the phenotypic ratio, it is first necessary to find the genotypes of the offspring. This is done by doing a Punnett square, as shown in linked photo.

https://vt-s3-files.s3.amazonaws.com/uploads/problem_question_image/image/41907/IMG_0517.jpg

Example Question #10 : Genetic Engineering

Two rams both have curly horns, which is a dominant trait. The recessive trait is straight horns. Is it possible that the offspring of these two rams will have straight horns?

Possible Answers:

no, because both rams have dominant alleles for curly horns

no, because both rams have genotypes for curly horns

yes, because it is possible that the two rams both carry a recessive allele for horn trait

yes, because although the two parent rams have curly horns, they both carry all recessive alleles that will produce offspring all with straight horns

Correct answer:

yes, because it is possible that the two rams both carry a recessive allele for horn trait

Explanation:

It is possible that the genotypes of both parent rams are Cc and Cc. This would mean that both parents carry the recessive allele for straight horns (c). By doing a Punnett square, we can see that there is a possibility of an offspring with straight horns.

https://vt-s3-files.s3.amazonaws.com/uploads/problem_question_image/image/41914/IMG_0518.jpg

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