Question 1

Suppose you have previously located and cloned a human gene on chromosome 2. You now believe there is an important disease-related gene nearby on the same chromosome. What technique might you employ to locate the disease-related gene?

Accepted Answer

Chromosome walking is a technique used to identify and sequence genes located near a known gene on a chromosome, making it suitable for locating a nearby disease-related gene.

Question 2

Use the following to answer questions You identify an RFLP in mice by digesting genomic DNA with HindIII enzyme and radiolabeling a piece of probe DNA. Southern blot analysis shows that the probe detects a 2-kb fragment in one strain of mice and a 4-kb fragment in another strain of mice. The two mice strains are crossed to produce an FS1U1B11S1U1B0 generation. Two FS1U1B11S1U1B0 siblings are mated to produce a dozen FS1U1B12S1U1B0 progeny. You isolate genomic DNA from several FS1U1B11S1U1B0 and FS1U1B12S1U1B0 individuals, digest with HindIII, and perform a Southern blot with the same probe. -How many bands would be seen in the Southern blot of an F₁ individual?

Accepted Answer

An F1 individual would be heterozygous, inheriting one allele from each parent, resulting in two different bands (2-kb and 4-kb) on the Southern blot.

Question 3

Explain what an RFLP is. Why do RFLPs behave like "codominant" markers?

Accepted Answer

The answer of Explain what an RFLP is. Why do...

Question 4

All of the following are required to create a cDNA library EXCEPT:

Accepted Answer

RNA polymerase is not required to create a cDNA library. Reverse transcriptase is used to convert mRNA into cDNA.

Question 5

Which of the following is usually NOT a component used to generate cDNA?

Accepted Answer

Restriction enzymes are not typically used in the process of generating cDNA; they are used to cut DNA at specific sequences.

Question 6

You have two probes that detect RFLPs that are closely linked. You have been asked to help settle a paternity case. The two possible fathers have the following RFLP pedigree. The child and mother are also probed with these two RFLP probes. (The data below the pedigree are two Southern blots.)  Which male is more likely to be the father? Explain your reasoning.

Accepted Answer

The answer of You have two probes that detect RFLPs...

Question 7

Which of the following DNA sequences are contained within a cDNA library?

Accepted Answer

A cDNA library is made from mRNA, which only includes exons, as introns, promoters, and enhancers are non-coding regions not present in mature mRNA.

Question 8

You are handling a paternity lawsuit brought against five potential fathers by a woman. You isolated DNA from the mother, the child, and all the potential fathers. After using PCR to amplify specific polymorphic loci from each individual, you run a gel of the amplified products and stain with ethidium bromide to visualize the DNA fingerprints (shown below). Mo = mother; Ch = child; M1-M5 = potential fathers. B1-B10 indicate marker bands present in the child. Do these results suggest that any of the men could be the child's biological father? Explain your answer.

Accepted Answer

The answer of You are handling a paternity lawsuit brought...

Question 9

One technique for finding a gene of interest involves first generating a genetic map to find the general location of the gene and then identifying the specific location of the gene. What is this technique called?

Accepted Answer

Positional cloning is a technique used to locate the position of a gene on a chromosome by first creating a genetic map and then narrowing down to the specific location of the gene.

Question 10

The lungfish Protopterus aethiopicus has a genome 38 times larger than that of humans. Most of the DNA in this species is noncoding repetitive DNA. What type of library would allow you to compare just the genes in lungfish to the genes in humans?

Accepted Answer

A cDNA library is made from mRNA and represents only the expressed genes, allowing for comparison of genes between species without the noncoding repetitive DNA.

Question 11

Which of the following statements is NOT correct?

Accepted Answer

Northern blot analysis uses nucleic acid probes, not antibodies, to detect RNA molecules.

Question 12

Which of the following statements is INCORRECT regarding the differences between a genomic library and a cDNA library?

Accepted Answer

Genomic libraries do not necessarily contain fewer restriction enzyme sites compared to cDNA libraries; this statement is incorrect.

Question 13

The full-length (i.e., containing the entire protein coding region) cDNA for a specific eukaryotic gene in humans is 1500 nucleotides long. You screen a pig genomic library with this cDNA and isolate two genomic clones of different lengths. Both clones are sequenced and found to be 1900 and 2100 nucleotides long from start codon to stop codon. How would you explain the presence of two genomic clones in pigs and the discrepancies in their lengths compared to the cDNA probe?

Accepted Answer

The answer of The full-length (i.e., containing the entire protein...

Question 14

Use the following to answer questions 
A fragment of DNA is cloned into a plasmid with a sequencing primer-binding site. After dideoxy sequencing, the gel pattern shown in this diagram is obtained. 
-What was the sequence of the DNA strand that acted as the template in the sequencing reaction?

Accepted Answer

The correct answer is A because the sequence of the DNA strand that acted as the template in the sequencing reaction is 5' GCTAGCA 3'. This is because the sequencing reaction is a process that uses a DNA polymerase to synthesize a new strand of DNA complementary to the template strand. The new strand is synthesized in the 5' to 3' direction, so the template strand must be in the 3' to 5' direction. The sequence of the template strand is therefore 5' GCTAGCA 3'.

Question 15

Use the following to answer questions You identify an RFLP in mice by digesting genomic DNA with HindIII enzyme and radiolabeling a piece of probe DNA. Southern blot analysis shows that the probe detects a 2-kb fragment in one strain of mice and a 4-kb fragment in another strain of mice. The two mice strains are crossed to produce an FS1U1B11S1U1B0 generation. Two FS1U1B11S1U1B0 siblings are mated to produce a dozen FS1U1B12S1U1B0 progeny. You isolate genomic DNA from several FS1U1B11S1U1B0 and FS1U1B12S1U1B0 individuals, digest with HindIII, and perform a Southern blot with the same probe. -How many bands would be seen in the Southern blot of an F₂ individual?

Accepted Answer

The F2 individuals are heterozygous for the RFLP, so they would have both the 2-kb and 4-kb fragments.

Question 16

A pedigree and Southern blot results in humans are shown in the following figure. Filled-in figures represent individuals expressing a dominant trait (hypothetical) for blue tongue. What can you say about the potential linkage relationship between the allele responsible for the trait? Shaded regions within the homologs represent sequences that hybridize to the probe used for the Southern analysis. Arrows indicate cleavage sites used for the Southern analysis.

Accepted Answer

The answer of A pedigree and Southern blot results in...

Question 17

You are trying to determine whether a certain RFLP marker is linked to a specific disease gene in dogs. A cross between a diseased male and a healthy female produces nine offspring. You isolate genomic DNA from parents and offspring, digest with EcoRI, radiolabel a portion of RFLP marker to use as a probe, and perform a Southern analysis. The pedigree and autoradiogram results are shown in the following figure. Assume that the disease is autosomal dominant.  (a) Explain the relationship between the crossing results (i.e., diseased versus healthy) and the RFLP patterns.

Accepted Answer

The answer of You are trying to determine whether a...

Question 18

Cloned eukaryotic genes are not always able to be expressed in bacterial cells. What are some possible reasons for this?

Accepted Answer

The answer of Cloned eukaryotic genes are not always able...

Question 19

What is the function of dideoxynucleotides in Sanger DNA sequencing?

Accepted Answer

Dideoxynucleotides lack a 3' hydroxyl group, which prevents the addition of further nucleotides, thus terminating DNA synthesis at specific sites. This allows for the determination of the DNA sequence by analyzing the lengths of terminated fragments.

Question 20

Which of the following is NOT used in an in situ hybridization experiment?

Accepted Answer

Antibodies are not used in in situ hybridization; they are typically used in immunohistochemistry or other protein detection methods.

Quiz 19: Molecular Genetic Analysis and Biotechnology