Exam 3- Quizzes, txtbook q's Flashcards
The antiparallel nature of DNA refers to
(a) Its charged phosphate groups
(b) The pairing of bases on one strand with bases on the other strand
(c) The formation of hydrogen bonds between bases from opposite strands
(d) The opposite direction of the two polynucleotide strands
(d) The opposite direction of the two polynucleotide strands
A plasmid has two antibiotic resistance genes, one for ampicillin and one for kanamycin.
The plasmid is cut with an enzyme that cuts within the middle of the ampicillin
resistance gene. DNA fragments containing the human ß-globin gene cut with the same
restriction enzyme are mixed with the digested plasmid. The mixture is then incubated
with DNA ligase and transformed into competent E. coli cells. Bacteria that have taken
up a recombinant plasmid containing the human ß-globin gene
a. are blue and can grow on plates with both antibiotics
b. can grow on plates with ampicillin but not with kanamycin
c. can grow on plates with kanamycin but not with ampicillin
d. are blue and can grow on plates with kanamycin
c. can grow on plates with kanamycin but not with ampicillin
When a dideoxynucleotide is incorporated into a growing DNA strand during DNA
replication,
a. the strand is elongated faster
b. the strand cannot be elongated
c. the strand becomes more susceptible to cleavage by a restriction endonuclease
d. the strand can be ligated into a cloning vector
b. the strand cannot be elongated
Which of the following is a type of mutation that relieves the effects of a previous
mutation?
a. loss-of-function mutation c. null mutation
b. suppressor mutation d. nutritional mutation
b. suppressor mutation
In population studies, the allele frequencies are commonly symbolized as
a. f b. p, q c. a, b d. p2, 2pq, and q2
b. p, q
- What is a spontaneous mutation, and why are spontaneous mutations rare?
- Why would a mutation in a somatic cell of a multicellular organism not necessarily result in a detectable phenotype?
. The extent to which a mutation changes the characteristics of an organism depends on the type of mutation (dominant or recessive), the type of cell affected (proliferating or nonproliferating), the number of cells affected, and the degree to which the mutation alters the function of the gene product or regulatory region. Mutations that occur in somatic cells are
not transmitted to the next generation but may lead to altered cellular function or tumors.
- Most mutations in a diploid organism are recessive. Why?
- What is the difference between a silent mutation and a neutral
mutation?
A silent mutation is a point mutation in an open reading frame that does not alter the amino acid encoded, due to degeneracy of the genetic code. A neutral mutation is one that occurs in noncoding DNA and does not affect gene products or gene expression.
- Contrast and compare the mutagenic effects of deaminating agents, alkylating agents, and base analogs.
. All three agents are mutagenic because they cause base substitutions, specifically transitions, but by different mechanisms. Deaminating agents oxidatively convert an amino group to a keto group. Alkylating agents donate an alkyl group to the amino or keto groups of nucleotides. Base analogs such as 5 bromouracil and 2-amino purine are incorporated as thymine and adenine, respectively, yet they base-pair with guanine and cytosine, respectively.
- In a population where only the total number of individuals with
the dominant phenotype is known, how can you calculate the
percentage of carriers and homozygous recessives?
. Assuming that the population is in Hardy–Weinberg equilibrium, if one has the frequency of individuals with the dominant phenotype, the remainder have the recessive phenotype
(q2). From this calculate q and then p, and apply the formula
2pq to determine the number of carriers.
Microbiologists describe the processes of transcription and translation as “coupled” in
bacteria. This indicates that a bacterial mRNA can be undergoing transcription at the same
time it is also undergoing translation.
a) How is coupling of transcription and translation possible in bacteria?
Because bacteria do not have compartmentalization like eukaryotes do. In bacteria the ribosomes and chromosomes are in the same place, the cytoplasm. So transcription and translation occur at the same time
Is coupling possible in single-celled eukaryotes such as yeast (a microorganism)? Why or
why not?
No, because eukaryotes are compartmentalize, the chromosomes are in the nucleus and the ribosomes are in the cytoplasm. The DNA goes through transcription in the nucleus. The resulting mRNA has to be modified and transferred outside of the nucleus in the cytoplasm and translated in the ribosomes.
Why is primase required for DNA replication?
DNA polymerase synthesizes nucleotides only when elongating an existing primer. primase synthesizes the primer which has a free 3’OH end. DNA polymerase can only start at a 3’OH end, once the primer is attached, DNA replication can start.
When creating a recombinant DNA molecule, what enzyme must be added to form a
phosphodiester bond between two DNA fragments with compatible sticky ends?
DNA ligase must be added to join the sticky ends
