Deck 16: Forward Genetics and Recombinant DNA Technology

Question 1

If mutagenizing a number of Drosophila results in several observable phenotypes but also in several lethal mutations,does this mean that recessive lethal mutations cannot be studied further?

A)No;the lethal allele can be recovered from heterozygous siblings.
B)No;the lethal alleles can be sequenced from the other embryos.
C)Yes;lethal alleles can be studied only if they are recessive.
D)Yes;lethal alleles can be studied only if they are conditional.
E)Yes;unless the lethal allele can be supplemented with a missing gene product.

Answer 1

A

Question 2

If a mutagenesis screen provides some number (e.g.,24)of alleles shown by complementation analysis to be in the same gene,which of the following is true?

A)These mutants can be used to identify the role of the gene in metabolism.
B)The gene being studied must be present in more than one copy per haploid genome.
C)The gene,in whole or in part,must be involved in transformation.
D)The gene must be highly conserved in evolution.
E)The gene must be involved in regulating a signal pathway.

Answer 2

A

Question 3

In 1978,Arber,Smith,and Nathans won the Nobel Prize in Physiology and Medicine for work with restriction enzymes.Which of the following can still be performed without using these enzymes?

A)PCR of whole genomes
B)genetic mapping
C)sequence cloning
D)vector packaging
E)making recombinant DNA

Answer 3

B

Question 4

Whether libraries are cDNA or genomic,whether amplification is based on PCR or cloning,and whether screening is done with northern or Southern blotting or probes,all are based on which of the following?

A)complementarity
B)complementation
C)reverse transcription
D)reverse translation
E)gene expression

Question 5

Because of redundancy in the genetic code,some amino acids can have more than one possible codon.Use the table above and select which of the answer choices is a possibility for the following amino acid sequence: valine,glycine,glycine,cysteine,tyrosine

A)GUU GGC GGA UGA UAG
B)GUA GGG GGG UGU UAC
C)GUG GGG GGA UAC UAC
D)GUA GGG GGC UGU UAC
E)GAU GGC GGC UGU UAU

Question 6

In a disease associated with a nucleotide repeat,anticipation is often noticed in subsequent generations,usually associated with a more severe phenotype.Which of the following is a more likely cause of anticipation?

A)There is more frequent unequal crossing over.
B)Subtle phenotypic nuances are more often sought by a physician.
C)Family members are exposed to the same mutagens.
D)Highly repeated sequences are expressed more often.
E)The sequences have greater stability in later generations.

Question 7

In the construction of a YAC library,each chromosome has the advantage of being able to hold very long DNA sequences.However,besides selectable marker(s)the YAC vector must minimally include which of the following?

A)a bacterial origin (ori)
B)cos site(s)and origin
C)centromere,telomeres,and yeast origin
D)centromere and origin
E)centromere and telomeres

Question 8

A researcher wants to mutagenize an organism.He is not in need of a large number of mutants but is more concerned with being able to find and then to amplify the mutated sequence.Which of the following would therefore be more useful?

A)ionizing radiation
B)UV radiation
C)transposon insertion
D)a chemical mutagen
E)search for spontaneous mutant

Question 9

Before Muller's discovery that radiation induces mutation,scientists had to work on mutations that were found solely by phenotype differences in natural populations.Which of the features of Drosophila made it a fortuitous choice for Morgan and his colleagues?

A)having a long life cycle
B)especially high rate of mutation
C)large number of easily visible phenotypes
D)well-known biochemical pathways
E)the number of genes with only two alleles

Question 10

You have a DNA sequence of 1600 bp.To characterize it,you decide to make a restriction map.Cutting with the first enzyme,you show by electrophoresis that the fragments produced are 400 and 1200 bp respectively.After using the second enzyme,you recover 700-bp and 900-bp fragments.After treatment with both enzymes,fragments were 300,400,and 900 bp.Which is the correct map?

A)-900 ------/400--/3---
B)-400/--900-----/300 ---
C)-300-/--400--/--900----
D)-400-/300-/---900-----
E)-400-/-100/--300--/900

Question 11

Which of the following would make a human disorder-causing allele or gene easiest to locate?

A)a genomic library for the chromosome on which the gene is located
B)a cDNA library for the chromosome on which the gene is located
C)a group of 10 known candidate genes
D)a transposon known to segregate with the gene
E)a single patient with a chromosomal translocation associated with the gene

Question 12

Some restriction enzymes cut at specific and unambiguous sequences (e.g.,NotI at GCGGCCGC).As such,the distance between two such sites in a large random DNA sequence is 4⁸.However,the sequence recognized by XhoII is said to be ambiguous (Pu-GATC-Py,where Pu = any purine and Py any pyrimidine).What,therefore,is the expected distance between two XhoII sites in a large random sequence?

A)4 × 4 × 4 × 4
B)1 × 4 × 4 × 4 × 4 × 1
C)2 × 4 × 4 × 4 × 4 × 2
D)4⁶
E)4² × 2²

Question 13

In producing a recombinant plasmid to be used to clone a given donor insert,it is possible to cut both the donor and plasmid with the same restriction enzyme,resulting in complementary sticky ends.Assuming plenty of plasmid DNA is available,why is further selection necessary before the introduction of the plasmid into a cellular system?

A)Contamination will have introduced other donor inserts.
B)Some donor inserts will be single stranded and deteriorate.
C)Some donor inserts will be sensitive to particular antibiotics.
D)Some donor pieces will remain uninserted.
E)Some donor strands will be inserted with an incorrect orientation.

Question 14

One use of PCR has been to monitor the trafficking of endangered organisms.Suppose that one suspect was accused of illegally importing a specific animal,but the suspect asserts that the young animal had been bred in this country from two resident zoo animals.How would you best proceed?

A)Use blood cells to obtain DNA from the animals and look for sequences found only in illegally traded ones.
B)Use DNA obtained from biopsy of the suspect organism and use a probe for infectious agents found more frequently in its native country.
C)Use DNA obtained from the possibly imported animal and treat with restriction enzyme;use a probe for disease genes common in its native country.
D)Use DNA from hair follicles of supposed zoo parents and of the supposed offspring to compare sequences amplified with primers for a highly polymorphic region
E)Amplify highly polymorphic regions from zoo and native populations to compare with the suspicious one.

Question 15

Current sequencing technologies have major advantages over the dideoxy method because they produce more sequence in less time and at less cost.Which of the following would provide further advantage?

A)being able to produce finer analysis of smaller sequences
B)the ability to produce primers for increasingly long sequences
C)the ability to sequence noncoding regions
D)sequencing very rare DNAs from degraded samples
E)sequencing without the need to amplify the DNA

Question 16

Among the attributes of model organisms,which of the following characteristics of C.elegans makes it useful for mutagenesis?

A)hermaphrodite reproduction
B)adults with ~1000 cells
C)self-fertilization of eggs with stored sperm
D)lack of a Y chromosome to determine gender
E)adults that mature in about 2 days

Question 17

Which of the following vectors would be most efficient to use to amplify fragments ~300 kb in length?

A)BACs
B)plasmids
C)YACs
D)lambda phage
E)cosmids

Question 18

In selecting recombinant bacteria,cells are chosen that are resistant to a specific antibiotic.How are the bacteria made resistant?

A)They are pre-selected for the experiment on this basis.
B)The antibiotic resistance is encoded in the vector.
C)The antibiotic resistance gene is encoded on the donor insert.
D)Resistance is activated by the recombination event.
E)Resistance is activated when the cells are provided with the antibiotic

Question 19

Genes for regulatory elements,such as creb,were found to be important in animal learning.Which of the following would increase the probability that such an element is studied throughout the animal kingdom?

A)its unique sequence in Drosophila
B)the finding that creb is highly conserved
C)the number of repeats of the creb gene
D)the interaction of creb with cAMP
E)the finding that creb activates odor perception

Question 20

In forensics,the laws in the United States and elsewhere allow the establishment of databases of PCR amplification of short tandem repeats (STRs)of the Y chromosome.Which of these statements would provide an appropriate basis for making such databases divided by ethnicity?

A)Different heritage groups have different levels of such polymorphisms.
B)It would be easier to evaluate suspects of different ethnicities.
C)It would show detectives which ethnic category they should be looking for.
D)Most crimes of certain types are found among certain groups.
E)Y polymorphisms increase with the probability of criminal behavior.

Question 21

Conditional alleles result in phenotypic differences in permissive as opposed to restrictive conditions.What do these conditions have in common?

Question 22

Each restriction enzyme comes from a particular bacterial strain.Why does a restriction enzyme not destroy the bacterial strain's own DNA?

Question 23

What method can you use to identify a gene when you know the amino acid sequence of a homologous protein?

Question 24

Which approach for sequencing large DNA molecules uses fragmentation that produces random but overlapping pieces?

Question 25

In mapping the HD gene associated with Huntington disease,eventually researchers narrowed down their hunt to four candidate genes within the mapped region.How did they identify one of these as the definitive HD gene?

Question 26

To produce a molecular clone requires amplification of a sequence via PCR or what other process?

Question 27

What genetically determines the difference in frequency of restriction fragments from two different enzymes used on the same genome?

Question 28

What kind of analysis is needed to determine whether two mutations are in the same gene or in different genes?

Question 29

Identifying an autosomal recessive mutation in a mutagenic screen in Drosophila requires identification of a mutant in the F₃ generation.If testing for a sex-linked recessive lethal mutation (e.g.,cn l + using a balancer chromosome such as cnCyO),in which generation can lines with mutations be identified?

Question 30

In a simple restriction mapping study,a sequence was cut by BamHI into one large and one small fragment.Cutting the same sequence with XhoI also results in two fragments.What can be done next to begin to map these sites?

Question 31

How can you use the known human cDNA gene sequence for cytC that you already have in an experiment(s)to identify and compare the sequences from other vertebrates?

Question 32

In positional cloning,the researcher begins with a phenotype.To move toward identification of its DNA sequence,she must begin with what step?

Question 33

For a contiguous sequence to be most useful in molecular mapping of a particular mutation,what should the contiguous sequence include?

Question 34

In a cDNA library,not all expressed genes will be represented.On what does this depend?

Question 35

How can blunt-ended DNA fragments be altered to allow them to be incorporated into a plasmid with sticky ends?

Question 36

DNA markers that are found to segregate with a mutation of interest can be used to determine the mutation's distance from the markers by looking at what?

Question 37

Suppose a scientist wants to identify a gene in a particular plant species by transposon tagging,but he is initially stumped because he finds no active transposons.He hypothesizes,however,that he can introduce a transposon from another plant species.Why might this be possible?

Question 38

In a given situation,reduced or missing function in gene A results in a viable but noticeable phenotype.The same is true for gene B.However,when both gene A and gene B products are reduced or missing in the same organism,the result is lethality.What is this called?

Question 39

Which type of DNA library (genomic or cDNA)would include introns and promoters?

Question 40

What technique of genomic library construction allows the genome to be cut by a given restriction enzyme at some but not all recognition sequences?

Question 41

Describe two or more ethical issues arising from sequencing the genomes of individuals.

Question 42

Should we allow (or urge)testing of minor age children or teens for adult-onset disorders for which there is no treatment or cure?

Question 43

A hypothetical restriction sequence is 5′-TCTAGA-3′.The palindromic sequence is 3′-________-5′.

Question 44

Why do we so frequently use mutant alleles to determine structure and/or function of the wild type?

Question 45

Would it be possible and/or appropriate to design a genetic screen to look for a gene(s)involved in homosexuality?

Question 46

In the process of identifying mutations in animals,dominant mutations can be found after one generation of mating between the mutagenized male organism and wild-type female.To identify the non-sex-linked (autosomal)recessive mutants requires ________ generations.

Question 47

A balancer chromosome includes a recessive lethal allele,a marker dominant allele,and ________.

Question 48

A genetic strategy that starts with knowing the DNA sequence and works toward identifying an associated phenotype is known as ________.

Question 49

Why is only a fraction of an organism's genes represented in any cDNA library?

Question 50

Specific sequences in the lambda genome that interact with coat proteins to package genomes into phage particles are known as ________ sites.