Genetics Chapter 16 Flashcards

Forward genetics

Reverse genetics

Forward genetics begins with...

Saturation mutagenesis

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

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

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

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

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.

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.

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

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

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

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.

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.

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

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

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.

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

...

C) centromere, telomeres, and yeast origin

A) complementarity