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).
True or False: A single gene mutation can change the phenotype of an organism.
A) True
B) False
A) True
Explanation: A mutation in a single gene can indeed change an organism’s phenotype, as genes directly control the traits by coding for proteins that determine cellular structure and function.
Fill in the blank: The ________ is a set of genes in bacteria that are regulated together and code for functionally related proteins.
Operon
Explanation: An operon is a functioning unit of genomic DNA containing a cluster of genes under the control of a single promoter. The genes are transcribed together into an mRNA strand and function in related processes.
Which of the following mutations does not change the amino acid sequence of the protein?
Options:
a) Missense mutation
b) Nonsense mutation
c) Silent mutation
d) Frameshift mutation
c) Silent mutation
Explanation: A silent mutation does not alter the amino acid sequence of a protein. This is because the genetic code is degenerate, meaning some amino acids are coded for by more than one codon.
True or False: All mutations are harmful to organisms.
A) True
B) False
B) False
Explanation: Not all mutations are harmful; some are neutral, and others can even be beneficial, providing genetic variation that can be advantageous in changing environments.
Fill in the blank: The process by which mRNA is decoded by the ribosome to produce a specific protein is called ____________.
Translation
Explanation: Translation is the step in protein biosynthesis where the genetic code carried by mRNA is decoded to produce a specific sequence of amino acids in a polypeptide chain.
What is the role of DNA polymerase I in DNA replication?
Options:
a) Adding bases to the new DNA chain
b) Unzipping the DNA helix
c) Removing RNA primers and replacing them with DNA
d) Binding DNA nicks during synthesis and repair
c) Removing RNA primers and replacing them with DNA
Explanation: DNA polymerase I plays a crucial role in DNA replication by removing RNA primers from the fragments of the lagging strand and replacing them with DNA nucleotides.
The genetic material of viruses can be composed of __________.
Options:
a) Only DNA
b) Only RNA
c) Either DNA or RNA
d) Neither DNA nor RNA
c) Either DNA or RNA
Explanation: Viruses can contain either DNA or RNA as their genetic material, which is unique among living organisms and viruses.
True or False: The lac operon is an example of a repressible operon.
A) True
B) False
B) False
Explanation: The lac operon is an inducible operon, not repressible. It is turned on (induced) by the presence of lactose, which it helps to metabolize.
Fill in the blank: The term __________ refers to the entire set of proteins expressed by a genome, cell, tissue, or organism at a certain time.
Proteomics
Explanation: Proteomics is the large-scale study of proteomes—sets of proteins produced in an organism, system, or biological context.
Which of the following is a characteristic of bacterial chromosomes?
Options:
a) They are linear and found in the nucleus.
b) They are usually single and circular.
c) They contain histones similar to eukaryotic chromosomes.
d) They are multiple and linear.
b) They are usually single and circular.
Explanation: Most bacteria have a single circular chromosome that contains their genetic material, unlike eukaryotes that have multiple linear chromosomes located in the nucleus.
True or False: Ribosomal RNA (rRNA) is directly involved in the process of translation.
A) True
B) False
A) True
Ribosomal RNA (rRNA) is a key component of ribosomes, which are the sites where translation—the process of synthesizing proteins from mRNA—occurs.
Fill in the blank: __________ are small, circular DNA molecules found in bacteria and some eukaryotes that can replicate independently of the main chromosomes.
Plasmids
Explanation: Plasmids are extrachromosomal DNA molecules that can carry genes beneficial for survival under certain conditions, such as antibiotic resistance genes.
What does the term ‘genotype’ refer to?
Options:
a) The physical appearance of an organism
b) The sum of all types of genes constituting an organism’s distinctive genetic makeup
c) The process by which genetic information is copied and transmitted to offspring
d) The structure of a specific protein
b) The sum of all types of genes constituting an organism’s distinctive genetic makeup
Explanation: The genotype of an organism is its complete set of genes, which determines its potential characteristics, distinct from its physical appearance or phenotype.
True or False: Only eukaryotic cells can perform the process of transcription.
A) True
B) False
B) False
Explanation: Both eukaryotic and prokaryotic cells can perform transcription, which is the process of copying a segment of DNA into RNA.
Fill in the blank: The __________ mutation changes a normal codon into a stop codon, potentially truncating the protein prematurely.
Nonsense
Explanation: Nonsense mutations alter the genetic code so that a stop codon replaces a codon that originally coded for an amino acid, leading to the premature termination of protein synthesis.
