LEC: Nucleic Acids Flashcards
Parts of a nucleotide
Base, monosaccharide, phosphate
Which bases are classified as purine?
Adenine, Guanine
Which bases are classified as pyrimidine?
Cytosine, Thymine, Uracil
A compound that consists of D-ribose or 2-deoxy-D-ribose bonded to a purine or pyrimidine base by a -N-glycosidic bond
Nucleoside
A nucleoside in which a molecule of phosphoric acid is esterified with an –OH of the monosaccharide, most commonly either at the 3’or the 5’–OH.
Guanidine 3’-triphosphate (3’-GTP)
Nucleotide
serves as a common currency into which energy gained from food is converted and stored.
Adenosine 5’-triphosphate (ATP)
Identify the structure: the sequence of nucleotides, beginning with the nucleotide that has the free 5’ terminus.
primary
Identify the structure: The ordered arrangement of nucleic acid strands.
secondary
A type of 2° structure of DNA in which two polynucleotide strands are coiled around each other in a screw-like fashion
Double helix
DNA is coiled around proteins called ____
histones
T/F: histones are rich in acidic amino acids with negative charge
F. They are rich in basic amino acids with positive charge
The negatively-charged DNA molecules and positively-charged histones attract one another and form units called _____.
nucleosomes
A core of eight histone molecules around which the DNA helix is wrapped.
Nucleosome
Nucleosomes are further condensed into _____
chromatin
Chromatin fibers are organized into loops, and the loops into the bands that provide the superstructure of _____
chromosomes
Enumerate the 3 differences in the structure of DNA and RNA
(1) DNA bases are A, G, C, and T; the RNA bases are A, G, C, and U.
(2) The sugar in DNA is 2-deoxy-D-ribose; in RNA it is D-ribose.
(3) DNA is almost always double stranded; there are several kinds of RNA, all of which are single-stranded.
This RNA transports amino acids to site or protein synthesis
tRNA (transfer)
This RNA combines with proteins to form ribosomes, the site of protein synthesis
rRNA (ribosomal)
This RNA directs amino acid sequence of proteins
mRNA (messenger)
This RNA processes initial mRNA to its mature form in eukaryotes
snRNA (small nuclear)
This RNA affects gene expression; important in growth and development
miRNA (micro)
This RNA affects gene expression; used by scientists to knowck out a gene being studied
siRNA (small interfering)
A segment of DNA that carries a base sequence that directs the synthesis of a particular protein, tRNA, or mRNA.
Gene
A section of DNA that, when transcribed, codes for a protein or RNA.
Exon
A section of DNA that does not code for anything functional
Intron
T/F: in bacteria, the gene is continuous
T
T/F: in higher organisms, the gene is continuous
F. It is discontinuous
T/F: there is only 1 gene in a single DNA molecule
F. there are many
_____ may lead to new treatments for cancer, infectious diseases, and chronic illnesses.
Manipulating RNA
____ drugs are already on the market with more in stages of clinical trials.
RNA-based
Enumerate the 2 functions of DNA in the chromosome
(1) It reproduces itself. This process is called replication.
(2) It supplies the information necessary to make all the RNA and proteins in the body, including enzymes.
Replication begins at a point in the DNA called the origin of replication or a _____
replication fork
This reaction eliminates some of the positive charges on histones and weakens the strength of the DNA-histone interaction
acetylation-deacetylation of lysine residues on histones
_____ temporarily introduce either single- or double-strand breaks in DNA
Topoisomerases (also called gyrases)
Once the supercoiling is relaxed, the broken strands are joined together and the _____ diffuses from the location of the replication fork.
topoisomerase
Replication of DNA molecules starts with the _____ of the double helix which can occur at either end or in the middle.
unwinding
Special unwinding proteins called _____, attach themselves to one DNA strand and cause the separation of the double helix.
helicases
short—4 to 15 nucleotides long—RNA oligonucleotides synthesized from ribonucleoside triphosphates. They are needed to initiate the primase-catalyzed synthesis of both daughter strands.
Primers
The enzyme enables complementary base pairing with high specificity.
DNA polymerase
Millions of copies of selected DNA fragments can be made within a few hours with high precision by a technique called _____
polymerase chain reaction (PCR)
Identify the structure: Order of bases in the polynucleotide sequence
primary
Identify the structure: Three-dimensional conformation of the polynucleotide backbone
secondary
Identify the structure: Supercoiling of the molecule
Tertiary
Identify the structure: Interaction with other classes of macromolecules, such as proteins
quaternary
_____ or _____ bases bonded to sugars, which in turn are bonded to phosphate groups
Purine, pyrimidine
Nitrogen-containing aromatic compounds that make up the coding portion of nucleic acids
Nucleic acid bases
Compounds that contain a six-membered ring
Pyrimidine
Compounds that contain a six-membered ring fused to a five-membered ring
Purine
Parent compounds of adenine and guanine
Purine
Lacks phosphate group (Nucleoside or nucleotide)
Nucleoside
Considered the normal, physiological DNA form
B-DNA
Right-handed helix, with an inner diameter of 11Å
B-DNA
10 base pairs per turn of the helix
B-DNA
Right-handed helix but thicker than B-DNA
A-DNA
11 base pairs per turn of the helix
A-DNA
T/F: A-DNA are often found in in vivo techniques
F. A-DNA are not found in in vivo techniques
Left-handed double helix
Z-DNA
May play a role in the regulation of gene expression
Z-DNA
Occurs in nature and usually consists of alternating purine-pyrimidine bases
Z-DNA
Produced by flipping one side of the backbone 180˚ without disturbing the backbone covalent bonds or hydrogen bonds
Z-DNA
In standard B-DNA, each base is rotated ____ (what angle) with respect to the preceding one
32°
Perfect for maximal base pairing but not optimal for maximum overlap of bases
B-DNA
T/F: Bases that are exposed to the major groove must come in contact with water
F. minor grooves must come in contact with water
Which is more optimal, base-pairing or base stacking?
Base stacking
Type of double-stranded DNA in which the 5′ and 3′ ends of each strand are joined by phosphodiester bonds
Circular DNA
Cut the phosphodiester backbone of one strand, pass the other end through, and reseal
Class I Topoisomerase
Cut both strands, pass some of the remaining DNA helix between the cut ends, and reseal
Class II Topoisomerase
Bacterial topoisomerase that introduces negative supercoils into DNA
DNA gyrase
Enzymes that relax supercoiling in closed circular DNA
Topoisomer (gyrase)
Complex of DNA and protein found in eukaryotic nuclei
Chromatin
T/F: the structure and spacing of nucleosome does not affect the chromatin function
F
Bases absorb light in the ____-wavelength region
260-nm
T/F: As the DNA is heated and the strands separate, the wavelength of absorption changes and the amount of light absorbed increases
F. the wavelength does not change
T/F: renaturation is possible in DNA
T (on slow cooling)
used to monitor the dissociation and reassociation of ribosomes
Analytical ultracentrifugation
Identify the RNA: Initially formed as a larger precursor molecule called heterogeneous nuclear RNA (hnRNA)
mRNA
Identify the RNA: Present in cells in relatively small amounts and is short-lived
mRNA
Identify the RNA: recently discovered
snRNA
Identify the RNA: Protection mechanism in many species, with the siRNAs being used to eliminate expression of an undesirable gene; used in the study of gene expression
RNA interference
Identify the RNA: used in the treatment of hepa C
miRNA
Identify the RNA: used in the treatment of ebola virus
siRNA
Used to develop treatments for cystic fibrosis and sickle-cell anemia
CRISPR (Cas)
Clustered regularly interspaced short palindromic repeats
CRISPR (Cas)
Promising and controversial model for study for future therapies
Long noncoding RNA (lncRNA)
Process of duplication of DNA
Replication
Process of formation of RNA on a DNA template
Transcription
Process of protein synthesis
Translation
_____ are those viruses in which RNA is the genetic material rather than DNA
Retroviruses
Enzyme that directs the synthesis of DNA on an RNA template
Reverse transcriptase
Retroviruses are catalyzed by ____
Reverse transcriptase
Scheme used to describe the manner in which information is transferred in a cell
Central dogma of molecular biology
DNA double helix unwinds at a specific point called an _____
origin of replication
Points at which new polynucleotide chains are formed
Replication forks
Bubble, or eye, of newly synthesized DNA between regions of the original DNA is a manifestation of the advance of the two replication forks in opposite directions
θ structure
Synthesized continuously from its 5′ end to its 3′ end at the replication fork on the exposed 3′ to 5′ template strand
Leading strand
Synthesized semidiscontinuously in small fragments, or Okazaki fragments
Lagging strand
Fragments are linked together by the enzyme _____
DNA ligase
This compound has been widely used in the treatment of AIDS (acquired immune deficiency syndrome), as has 2′-3′-dideoxyinosine (DDI)
3′-azido-3′-deoxythymidine (AZT)
Number of nucleotides incorporated before the dissociation of enzyme from the template
Processivity
T/F: DNA polymerase catalyzes de novo synthesis
F. DNA cannot catalyze de novo synthesis
Identify the DNA polymerase: Repairing and patching DNA
DNA pol I
Identify the DNA polymerase: Polymerization of the newly formed DNA strand
DNA pol III
Identify the DNA polymerase: Repairing enzymes
DNA pol II, IV, V
Removing incorrect nucleotides during DNA replication
Proofreading
Removing incorrect nucleotides from DNA and replacing them with correct ones
Repair
2 exonuclease activities
Proofreading and repair
Complex of DNA polymerase, the RNA primer, primase, and helicase at the replication fork
Replisomes
Catalyzes reactions involving relaxed, circular DNA with a nick in one strand to the supercoiled form with the nick sealed
DNA gyrase: Class II topoisomerase
Prokaryotic DNA is _____ (positively/negatively) supercoiled
negatively
Opening the helix during replication introduces _____ (positive/negative) supercoils ahead of the replication fork
positive
DNA gyrase fights _____ (positive/negative) supercoils
positive
Stabilizes single-stranded regions by binding tightly to them
Single-strand binding protein (SSB)
Promotes unwinding by binding at the replication fork
Helicase
Helix-destabilizing protein
Helicase
T/F: Primer activity was first observed in vivo
T
____ serves as a primer in DNA replication
RNA
Enzyme that makes a short section of RNA to act as a primer for DNA synthesis
Primase
Complex at the replication fork that consists of the RNA primer, primase, and helicase
Primosome
Errors in replication that occur spontaneously only once in every 109–1010 base pairs and can be lethal to organisms
mutations
Cut-and-patch process catalyzed by _____ (what polymerase) takes place during replication
Pol I
Removal of RNA primer or DNA mistakes by Pol I using its 5′ → 3′ exonuclease activity as it moves along the DNA and then filling in behind it with its polymerase activity
Nick translation
Agents that bring about a mutation
mutagens
Leads to a break in phosphodiester backbone of the DNA strand
Free radicals
Creates pyrimidine dimers
UV light
___ electrons from two carbons on each of the two pyrimidines form a cyclobutyl ring that distorts the normal shape of the DNA
π
In BER, the damaged base is removed by _____
DNA glycosylase
Identify the damage: Pose a big threat to the stability of the genome
Double-stranded breaks (DSB)
Natural process in which genetic information is rearranged to form new associations
Genetic recombination
DNA recombination occurs in specific zones of the chromosome, which are called _____
hot spots
Describes how recombination occurs by the breakage and reunion of DNA strands so that physical exchange of DNA parts takes place
Holliday model
Which is more complicated, eukaryotic or prokaryotic DNA replication?
Eukaryotic
Enumerate the reasons why eukaryotic DNA replication is more complicated
Multiple origins of replication
Need to control the timing to that of cell divisions
Involvement of more proteins and enzymes
Identify the eukaryotic replication complex: Bound to the DNA throughout the cell cycle but serves as an attachment site for several proteins that help control replication
Origin recognition complex (ORC)
Identify the eukaryotic replication protein: Protein whose binding prepares for the start of DNA replication
Replicator activator protein (RAP)
Identify the eukaryotic replication factor: Proteins that are essential for DNA replication; Some are cytosolic
Replication licensing factors (RLFs)
Combination of the DNA, ORC, RAP, and RLFs that makes DNA competent for replication
Pre-replication complex (pre-RC)
Proteins that are produced in one part of the cell cycle and degraded in another
Cyclins
Cyclins combine with _____
cyclin-dependent protein kinases (CDKs)
Eukaryotic replication: In the ___ phase, DNA has been replicated
G2
Identify the polymerase: Makes primers
Polymerase α
Identify the polymerase: Principal DNA polymerase in eukaryotes
Polymerase δ
Identify the polymerase: Involved in leading strand replication
Polymerase ε
Identify the polymerase: a repair enzyme
Polymerase β
Identify the polymerase: carries out DNA replication in mitochondria
Polymerase γ
This polymerase interacts with PCNA (proliferating cell nuclear antigen)
Polymerase δ
This polymerase may replace polymerase δ in lagging strand synthesis
Polymerase ε
Eukaryotic equivalent of the part of Pol III that functions as a sliding clamp (β)
PCNA
Trimer of three identical proteins that surround the DNA
PCNA
Special structures found in the ends of eukaryotic chromosomes
Telomeres
Ribonuclear protein that contains a section of RNA that is the complement of the telomere
Telomerase
Function of telomerase
Provides a mechanism for synthesis of telomeres; reactivated in cancer cells