BIO 101 - Ch. 11 Quiz

Classify the statements below as relating to preimplantation genetic diagnosis (PGD). Some labels might be used more than once. Others might not be used.

- Tests for genetic sequences in embryos - Uses DNA probes

Select all the reasons why STRs are commonly examined in DNA profiling.

- The chances are extremely low that the STR pattern at all loci is identical between two unrelated individuals. - STRs are extremely variable and have many possible alleles at each site.

Classify the items as true of stem cells.

- Undifferentiated - More common early in development than late in development - Totipotent

Extracting a nucleus from a sheep cell and fusing it with the egg cell of a second sheep of the same species produces the first cell of a transgenic organism. (True/False)

False

Below are the first few paragraphs of a hypothetical popular science article about the use of CRISPR-Cas9 in human cells. Read the excerpt, and then answer the question that follows. In recent years, a gene-editing system called CRISPR-Cas9 has revolutionized the world of biotechnology. Scientists use an enzyme called Cas9 to cut a specific sequence of DNA. How does Cas9 know where to cut? A short strand of "guide RNA" forms complementary base pairs with the gene and shows Cas9 where to bind. The Cas9 enzyme then comes into place on top of the DNA and cuts each strand. Theoretically, Cas9 cuts DNA precisely where researchers ask it to cut and no where else. However, researchers at Massachusetts General Hospital and Harvard Medical School have uncovered a potential problem with editing the human genome: Cas9 often makes incorrect cuts. How did the researchers conduct their experiment? First, they constructed several different guide RNAs that bind to specific sequences of human DNA. Then, they unleashed the guide RNAs and Cas9 enzymes into human cells in the laboratory and observed where the DNA got cut. They found that the guide RNA often improperly attached to DNA at sites where base pairing was imperfect; Cas9 then cut the incorrect site. While, on average, the target sequence was the most likely site to be cut, sites that differed from the target sequence by one or two nucleotides were also frequently cut by Cas9. Based on this excerpt, which graph would you expect to find in the scientist's article?

(Graph w/negative slope and scatter dots)

Below are several statements about how CRISPR-Cas9 can be used. Select all that are true.

- CRISPR-Cas9 can modify which proteins a cell produces. - CRISPR-Cas9 can silence genes. - CRISPR-Cas9 can insert a mutation into a gene. - CRISPR-Cas9 has the potential to change the evolution of a species.

What ethical issues are associated with medical uses of DNA technology? Select all that apply.

- Gene therapy could potentially be used not only for life-threatening illnesses, but also to enhance certain traits. - Genetic tests could be used to screen embryos for desirable traits, such as eye color or sex. - Genetic testing that allows early diagnosis of risk for a disease can potentially cause depression or anxiety in the individual and decrease effectiveness of treatment.

Classify the items as true of specialized cells.

- Number of divisions is limited - Differentiated, in most cases

Why it is useful to be able to rapidly make many copies of a piece of DNA using PCR? Select all that apply.

- PCR is used in preimplantation genetic diagnosis (PGD) and in genetic testing to copy a small sample of DNA until there is enough of it to analyze. - PCR is used to create a genetic profile of a sample taken from a crime scene.

Click on the true statements about DNA. Select all that apply.

- Scientists use DNA sequences to determine guilt in legal cases - Doctors analyze DNA sequences to screen for diseases - The DNA sequence of genes is passed from parents to their offspring - The sequence of mitochondrial genes provides information about human evolution, disease, and inheritance patterns - The sequence of our DNA determines the shape and function of our proteins

Classify the statements below as relating to gene therapy. Some labels might be used more than once. Others might not be used.

- Supplements faulty genes - Uses viruses

Classify the statements below as relating to genetic testing. Some labels might be used more than once. Others might not be used.

- Tests for genetic sequences in developed individuals - Uses DNA probes

Put the labels in the correct sequence to describe how researchers create a transgenic plant.

- Use restriction enzymes to create a recombinant plasmid - Insert recombinant plasmid into bacterium - Infect plant cells with transgenic bacterium - Bacterium inserts recombinant plasmid into plant cell DNA - DNA replication and cell division within plant cells produce multiple copies of recombinant DNA

What are some effects of gene therapy? Select all that apply.

- insert "healthy" genes into cells - silence genes that cause diseases - potentially enhance performance or appearance

Suppose scientists created transgenic crops that express a bacterial protein called Bt toxin. Arrange the following steps for creating a Bt crop in the correct order.

1. Bt gene is extracted from Bacillus 2. Bt gene is inserted into bacterial plasmid 3. Bacterium injects plasmid into plant cells 4. Plasmid becomes incorporated into plant DNA 5. Plant RNA polymerase transcribes Bt gene 6. Plant ribosomes translate mRNA from Bt gene

Arrange the steps for DNA profiling in order from first to last.

1. Obtain DNA from a sample, such as blood or hair roots 2. Amplify DNA with PCR 3. Determine the number of STR repeats at a site in both homologous chromosomes 4. Generate DNA profile listing genotypes for all STR sites 5. Compare DNA profile to sample of interest, such as potential family member or suspect

Match each of the terms associated with DNA technology to their correct descriptions. 1. Probe 2. Gene Therapy 3. Somatic Cell Nuclear Transfer 4. Clones 5. Transgenic Organisms 6. CRISPR-Cas9 7. Electrophoresis

1. Piece of DNA used to detect complementary pieces of DNA 2. Technique that uses viruses to deliver "healthy" DNA into cells that have defective genes 3. Technique for producing cloned animals 4. Organisms with the exact same DNA as each other 5. Organisms that contain their own DNA and DNA from a different species 6. Molecular machinery cuts a sequence of target DNA 7. Technique used to separate pieces of DNA produced during DNA sequencing

Scientists want to test if amoebas have an allele for a particular gene. They create many copies of a fluorescent probe to inject into the amoebas. To which DNA sequence will the probe bind? Probe sequence: 5' - GTACGTGTATGT - 3'

3' CATGCACATACA 5'

A DNA restriction enzyme cuts DNA at a specific sequence. If a restriction enzyme that cuts at the DNA sequence GAATTC were used on the DNA strand below, and the resulting fragments were put through electrophoresis, how many bands would appear on the electrophoresis gel?

4

In the process of DNA sequencing, what happens when DNA polymerase adds one of the "terminator" nucleotides?

A DNA fragment is produced that ends in that specific "terminator" nucleotide.

Sequences of a few nucleotides that vary in number of repeats and are used in DNA profiling are called

STRs

What situation best represents how DNA sequencing, PCR, and gene probes might be used together?

Scientists might replicate a strand of DNA using PCR before sequencing it. Once the sequence is known, they can produce a corresponding gene probe.

Place the following genetic elements in order from smallest to largest.

Smallest 1. Adenine 2. Gene 3. Plasmid 4. Chromosome 5. Genome Largest