Chapter 6 Practice Exercises Flashcards
During DNA replication, the _________ strand is synthesized continuously while the _________ strand is synthesized in a series of short fragments called Okazaki fragments.
Multiple Choice
A) parallel; antiparallel
B) forward; backward
C) leading; lagging
D) 5’; 3’
C) leading; lagging
Explanation: The leading strand is synthesized continuously in the 5’ to 3’ direction. Since DNA polymerase can only build DNA in the 5’ to 3’ direction, the lagging strand is synthesized in short fragments called Okazaki fragments which are later joined by DNA ligase.
Select the statements that are true of inducible operons to test your understanding of the differences between inducible and repressible operons.
Check All That Apply
A) Inducible operons often contain genes for enzymes that function in catabolic processes.
B) Inducible operons are usually in the “turned on” state and are ‘turned off’ when not needed.
C) The inducer is often the product of the enzymes encoded.
D) Inducible operons will be “turned on” in the presence of the substrate and turned off in its absence.
E) The lac operon is an example of an inducible operon.
A) Inducible operons often contain genes for enzymes that function in catabolic processes.
D) Inducible operons will be “turned on” in the presence of the substrate and turned off in its absence.
E) The lac operon is an example of an inducible operon.
Explanation: Inducible operons usually encode enzymes required for catabolic processes. This means that the enzymes necessary for the catabolism of that substrate will only be produced when that substrate is present. These operons are in the “off” state when the substrate is absent. The lac operon is an example of an inducible operon.
The specific sequence of 3 bases in mRNA that encodes a particular amino acid is the _________ whereas the complementary sequence of 3 bases in tRNA that bind to the mRNA is known as the _________.
Multiple Choice
A) gene; locus
B) codon; anticodon
C) 5’ cap; 3’ poly A tail
D) primer; telomere
B) codon; anticodon
Explanation: The specific sequence of 3 bases in mRNA that encodes a particular amino acid is the codon. The sequence of 3 complementary bases on tRNA that binds to the codon temporarily during translation is known as the anticodon. This complementary matching of the codon and anticodon is what ensures the correct amino acid is delivered to the chain based on the code in mRNA.
Select the statements that are true of repressible operons to test your understanding of the differences between inducible and repressible operons.
Check All That Apply
A) Repressible operons often contain genes for enzymes that digest sugars.
B) Repressible operons are usually the “turned on” state and are “turned off” when their product is in adequate supply.
C) The product of the enzymes in the operon functions as a corepressor.
D) Repressible operons will be “turned on” in the presence of the product and turned off in its absence.
E) Enzymes necessary for the synthesis of amino acids are often encoded by genes in repressible operons.
B) Repressible operons are usually the “turned on” state and are “turned off” when their product is in adequate supply.
C) The product of the enzymes in the operon functions as a corepressor.
E) Enzymes necessary for the synthesis of amino acids are often encoded by genes in repressible operons.
Explanation: Repressible operons often encode genes involved in biosynthetic pathways, such as the pathways needed to synthesize amino acids. The operons are usually in the “on” position. When an adequate supply of the product of the enzymes in the operon is present in the cell, this product will act as a corepressor needed to block the transcription of the operon. Thus the product turns off the operon.
Evaluate the statements below, and select those that correctly apply to the mechanisms of conjugation, transformation, and transduction.
Check All That Apply
A) Conjugation requires a gene on the bacterial chromosome to code for a sex pilus, through which the chromosome passes from donor to recipient.
B) Certain cells, called F+ cells, contain a plasmid that codes for a sex pilus to connect to a recipient F- cell and donate a copy of the plasmid.
C) When bacteriophage progeny are being assembled, occasionally a fragment of host DNA is packaged in error and transferred to a new cell by the process of transduction.
D) In the process of transduction, soluble DNA from the environment is accepted by a competent cell and is integrated into the recipient’s genome.
E) During transformation, DNA is transferred from one bacterial cell to another in the capsid of a bacteriophage.
F) During transformation, DNA that has been released from a dead cell passes through the cell wall of a competent cell.
B) Certain cells, called F+ cells, contain a plasmid that codes for a sex pilus to connect to a recipient F- cell and donate a copy of the plasmid.
C) When bacteriophage progeny are being assembled, occasionally a fragment of host DNA is packaged in error and transferred to a new cell by the process of transduction.
F) During transformation, DNA that has been released from a dead cell passes through the cell wall of a competent cell.
Select the types of RNA that are directly involved in translation.
Check All That Apply
A) tRNA
B) rRNA
C) xRNA
D) mRNA
E) Antisense RNA
A) tRNA
B) rRNA
D) mRNA
Explanation: The three types of RNA involved in translation are messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA).
DNA replication is described as
Multiple Choice
A) dispersive.
B) conservative.
C) semiconservative.
D) disruptive.
C) semiconservative.
Explanation: DNA replication is semiconservative, where each parent strand serves as a template for the formation of a duplicate strand of DNA. The resulting double-stranded DNA molecules will each contain one original and one new strand.
The genetic makeup of an organism is referred to as its _________ whereas the observable traits due to gene expression are referred to as its _________.
Multiple Choice
A) genotype; phenotype
B) haplotype; phenotype
C) phenotype; genotype
D) genotype; proteotype
A) genotype; phenotype
Explanation: The genetic makeup of an organism is its genotype. The observable traits or characteristics of an organism constitute its phenotype. The phenotype is the result of the interaction of the genotype and the organism’s environment.
Select the mechanisms below which enable the horizontal transfer of antibiotic resistance genes.
Check All That Apply
A) Transformation
B) Transduction
C) Transcription
D) Translation
E) Conjugation
A) Transformation
B) Transduction
E) Conjugation
Explanation: Antibiotic resistance genes can be spread by any of the horizontal gene transfer mechanisms used by bacteria which include transformation, transduction, and conjugation.
Select all of the features that you would include if you drew a short segment of DNA.
Check All That Apply
A) Double-stranded
B) Single-stranded
C) Helical shape
D) Chains of nucleotides
E) Nucleotides are base-paired with T bonded to A and C bonded to G through hydrogen bonds
F) Nucleotides contain ribose
G) Backbone comprised of sugar and phosphate groups
A) Double-stranded
C) Helical shape
D) Chains of nucleotides
E) Nucleotides are base-paired with T bonded to A and C bonded to G through hydrogen bonds
G) Backbone comprised of sugar and phosphate groups
Explanation: A diagram of DNA should show a double helix of two nucleotide chains. The nucleotides in each chain are bonded through their deoxyribose sugar and phosphate groups. The nucleotides of one chain are base-paired with those of the other chain with hydrogen bonds between their nitrogenous bases. As are bonded to Ts, and Cs are bonded to Gs.
What is the term used for the sum total of genetic material of an organism?
Options:
a) Chromosome
b) Gene
c) Genome
d) Plasmid
c) Genome
Explanation: The genome refers to all the genetic material present in an organism, including chromosomes and, in some cases, plasmids.
True or False: DNA polymerase III can begin synthesizing a new strand of DNA without a primer.
A) True
B) False
B) False
Explanation: DNA polymerase III requires a primer to start DNA synthesis because it can only add nucleotides to an existing strand.
Fill in the blank: The process by which DNA is copied before a cell divides is called ____________.
DNA replication
Explanation: DNA replication is the process of making two identical replicas from one original DNA molecule. This process is essential before a cell divides to ensure that each new cell receives an exact copy of the DNA.
Which RNA type carries the genetic information from DNA to the ribosome for protein synthesis?
Options:
a) mRNA
b) tRNA
c) rRNA
d) siRNA
a) mRNA
Explanation: Messenger RNA (mRNA) carries the genetic blueprint from DNA in the nucleus to the ribosome, where proteins are synthesized.
The transfer of DNA from one bacterium to another by a bacteriophage is known as ________.
Options:
a) Conjugation
b) Transformation
c) Transduction
d) Replication
c) Transduction
Explanation: Transduction is the process by which DNA is transferred from one bacterium to another via a bacteriophage (a virus that infects bacteria).
