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115 Cards in this Set
- Front
- Back
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Carbon is an abundant element in biological molecules because it
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forms stable covalent bonds by electron pair sharing.
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A triglyceride is a molecule
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with a glycerol backbone and three fatty acid chains attached.
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The central dogma of Molecular Biology is
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DNA is transcribed into RNA which is translated into protein.
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Which of the following statements regarding proteins is TRUE?
a. A protein that is non-covalently linked to a carbohydrate is called a glycoprotein. b. Peripheral membrane proteins are embedded within the plane of the membrane. c. Proteins are required for the transport of small hydrophobic solutes across cell membranes. d. Proteins are found in heterochromatin, ribosomes and phospholipids. e. The sequence of a protein is read from its N-terminal end to its C-terminal end. |
e. the sequence is read from its N-terminal to its C-terminal
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Which of the following is/are NOT found in BOTH prokaryotic and eukaryotic cells?
a. Cytoplasm b. Genetic material c. Plasma membrane d. Ribosomes e. Organelles |
e. organelles
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The plasma membrane of cells is referred to as a fluid mosaic because:
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: Both proteins and phospholipid molecules move laterally within the membrane.
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Which of the following statements is FALSE
a. Both mitochondria and chloroplasts are surrounded by double membranes. b. Mitochondria are the site of cellular respiration in cells. c. Mitochondria contain thylakoids. d. Chloroplasts contain DNA. e. Chloroplasts are photosynthetic organelles. |
C. mitchondria contain thylakoids
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The nuclear membranes of eukaryotic cells are continuous with
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endoplasmic reticulum
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The main technique used by Watson and Crick to determine the structure of double stranded DNA was:
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X-ray diffraction
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The DNA polymerases of E. coli have
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different affinities for dNTPs.
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A primer is essential for DNA replication. A primer is:
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A short single stranded sequence of RNA or DNA
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Together with _______________, ________________ provides for genetic variability within species and, ultimately, the evolution of new species.
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recombination; mutation
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A gene promoter is
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normally upstream from the gene it is promoting
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Which of the following statements about promoters is FALSE?
a. They consist of three nucleotides that bind to a codon. b. They are binding sites for RNA polymerase. c. They are specific nucleotide sequences of DNA. d. The determine which DNA strand is used as a template. e. They determine the position where RNA synthesis begins. |
A. they consist of three nucleotides that bind to a codon
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Which of the following statements is TRUE?
a. Ribosomes are large RNA structures composed solely of rRNA. b. Prokaryotic and eukaryotic ribosomes show no structural similarities. c. rRNA contains the catalytic activity that joins amino acids together. d. A ribosome consists of two equally sized subunits. e. A ribosome binds one tRNA at a time. |
c. rRNA contains the catalytic activity that joins amino acids together
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All are true for translation in eukaryotic cells except?
a. transcription and translation are spatially separated. b. mRNAs are monocistronic. c. transcription occurs in the nucleus. d. primary transcripts undergo processing to mature mRNAs. e. All the answers are true. |
e. all answers are true
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Ribosomes are
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comprised of a small and a large subunit.
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The adaptor molecules that interact specifically with both nucleic acids and amino acids to bridge the information gap are
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tRNA molecules
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Which inhibitor of protein synthesis competes with aminoacyl-tRNAs for binding to the A site of the ribosome?
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tetracycline
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On what basis does the aminoacyl tRNA synthetase attach the correct amino acid to the appropriate tRNA?
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the shape of the tRNA
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Noncovalent interactions that can form between the atoms of a polypeptide’s backbone and the atoms of its side chain (R) group include all except
a. disulphide bonds b. hydrophobic interactions c. hydrogen bonds d. van der Waals attractions e. ionic bonds |
a. disulphide bonds
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α-helix and β-strand are components of ______________ structure.
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secondary
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Two proteins found in the same cluster on the branch of an evolutionary tree will typically show
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high sequence and high functional similarities.
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Which of the following statements is FALSE?
a. Many proteins have more than one binding site. b. Proteins are designed to bind their ligands as tightly as possible. c. Changes in the amino acid sequence of a protein can decrease binding to a ligand, even if the altered amino acid does not lie in the binding site for the ligand. d. The three dimensional structure of a protein dictates its function by determining its binding specificity for other molecules. e. Binding between protein and ligand generally involves noncovalent bonds. |
b.Proteins are designed to bind their ligands as tightly as possible.
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All of the following are used to clone a DNA fragment EXCEPT
a. DNA ligase. b. DNA methylase. c. bacterial cells. d. plasmids. e. restriction enzymes. |
b.DNA methylase
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In the large-scale production of a particular human protein in E. coli cells, the cDNA corresponding to the protein was modified so that the expressed protein would have six histidine residues at the C-terminus. The purpose of this modification was
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to facilitate purification of the expressed protein though binding to an affinity column containing nickel atoms.
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What are the names given to proteins that control gene transcription and bind to regulatory elements on DNA and how are they categorised?
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They are known as transcription factors, and are categorised as either general OR cell/tissue specific transcription factors.
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In eukaryotes, chromosomes do not contain
a. proteases. b. histones. c. DNA. d. proteins. e. chromatin. |
a.proteases
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Which of the following is NOT a standard type of pre-mRNA processing to produce a mature mRNA in eukaryotes?
a. Addition of a 5’ cap. b. Addition of a polyA tail. c. Binding of transcription factors. d. Splicing to remove introns. e. Co-transcriptional modifications. |
c. binding of transcription factors
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What is the result of the process of alternative splicing to a cell?
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It means that from one gene, a number of different proteins can be produced
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The correct sequence of events in the cell cycle is:
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G1, S, G2, M
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Which of the following statements about mitosis and meiosis is FALSE?
a. Mitosis produces cells of the same ploidy; meiosis produces haploid cells from diploid cells. b. Mitosis produces identical daughter cells; meiosis produces four different daughter cells. c. Meiosis has two consecutive divisions; mitosis has one. d. Cytokinesis usually occurs at the end of each. e. Mitosis involves pairing homologous chromosomes; meiosis does not. |
e. mitosis involves pairing of homologous chromosomes, meiosis does not
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Which of the following statements is FALSE?
a. Cell proliferation and apoptosis pathways are not linked. b. Cell proliferation is controlled by cell cycle checkpoints. c. In multicellular organisms, somatic cells may be eliminated by apoptosis. d. Protein kinases modulate activities of proteins regulating the cell cycle. e. Executioner caspases are involved in apoptosis |
a. cell proliferation and apoptosis pathways are not linked
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Which of the following statements is TRUE?
a. Cyclin-dependent kinases become activated when they interact with one another. b. Cyclin-dependent kinase complexes consist of cyclin dependent kinases and target proteases. c. Cyclin-dependent kinase levels vary with cell cycle phase. d. Cyclin levels vary with cell cycle phase. e. Two of the above statements are correct. |
d. cyclin levels vary with cell cycle phases
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Mitosis and meiosis enable maintenance of genetic continuity in eukaryotes. Which of the following statements best summarises these processes?
a. None of the statements is fully correct. b. Both mitosis and meiosis produce progeny cells with exact replicas of the parental DNA. c. Mitosis and meiosis are identical, except meiosis only occurs in gamete production. d. Homologous chromosomes remain associated throughout the process of meiosis, but not mitosis. e. Replication of DNA is the only important process in both mitosis and meiosi |
a. non of the statements are fully correct
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Which of the following represent the cell cycle stages in which the three main check points within the cell cycle occur?
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G1, G2, M
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Phases of cell cycle in order
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Interphase, Prophase, Prometaphase, Metaphase, Anaphase, Telophase
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Regarding connection of microtubules to kinetochores, one statement is FALSE
a. The microtubules from centrioles meet the kinetochore by chance. b. Correct attachments of microtubules to the kinetochore are stable and under tension. c. Incorrect or absent connections makes microtubules unstable, which favours reconnection. d. If a kinetochore is not attached to a microtubule, the cell cycle checkpoint remains active. e. Once attached, microtubules pull the centrioles towards the kinetochore during cell cleavage |
e. once attached, microtubules pull the centrioles toward the kineochore during cell cleavage
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Cell membranes are comprised largely of
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phospholipid bilayers with each leaf of the bilayer different and amphipathic
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The pores of the cell nucleus
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are much larger than the protein "pores" through the cell lipid bilayers.
contain sub-structures called filaments. contain a structure called an annulus. contain a structure called a cage. |
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One statement is FALSE. Regarding pores, ports and pumps
a. pores form a water-filled channel through the lipid bilayer. b. ports do not form a water-filled channel through the lipid bilayer. c. pumps are very similar to carriers but utilize a fuel molecule directly. d. pores always allow non-polar solutes through, but select between ions. e. polar solutes cannot pass through the lipid bilayer without transport proteins. |
d. pores always allow non-polar solutes through, but select between ions
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The process of synthesising ATP within mitochondria relies on
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a process known as chemiosmosis.
a membrane transport pump driven backwards by a proton gradient. an H+ concentration gradient across the inner lipid bilayer. |
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One statement is FALSE. Regarding biochemical messengers within cells,
a. they often operate via phosphorylation of target proteins. b. common messengers are IP3 and cAMP. c. the process always begins by opening specific membrane channels d. common messengers are cAMP and cGMP. e. a common ion in biochemical cascades is Ca2+ |
c. the process always begins by opening specific membrane channels
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A GTP-binding protein most often has three subunits known as
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the alpha, beta and gamma subunits.
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The three major organelles in animals/plants that are surrounded by double membranes are
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the nucleus, the chloroplasts and the mitochondria.
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what is the base sequence of DNA strand complementary to
5'GCAATCCG3' |
3'CGTTAGGC5'
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bases in RNA and DNA
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Guanine, cytosine, thymine, adenine and uracil
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purines(A&G) base pair with?
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pyrimidines (C&T/U)
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which bases form a triple hydrogen bond
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cytosine and guanine
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4 important characteristics of DNA
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1. 1:1 ratio between pyrimidines and purine residues
2. hydrogen bonding between base pairs 3. information contained in the sequence of one strand is conserved in the sequence of the other strand 4. information is assessed through transcription of the information into RNA |
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Is DNA replication conservative or semi conservative
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semi conservative
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DNA polymerization occurs by addition of a deoxyribonucleotide to what chemical group?
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3' hydroxyl group
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what is an okazaki fragment?
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a segment of DNA on the lagging strand which is growing in the 5' to 3' direction
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are thymine dimers formed by adjacent thymines in the same strand or between opposite thymines?
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adjacent
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_________ promotes the formation of covalent bonds between _______ thymine residues in a DNA strand to create a thymine dimer
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UV light; adjacent
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mutation of DNA can occur in all except
a. spontaneous mutation due to replication errors b. infectious agents c. errors in transcription d. chemical mutagens e. transposable elements |
c. errors in transcription
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immediately after translation in the cell
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primary transcript is altered by polyadenlyation
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What direction does RNA polymerase move along the template strand
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3' to 5'
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the strand of double stranded DNA that is read by the RNA polymerase is termed the _____ strand with RNA polymerase moving ________ along it making the __________ in the _______ direction
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template strand; 3' to 5'; transcript; 5' to 3'
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what are the factors or subunits contained in E.coli RNA polymerase
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alpha, beta, beta prime, sigma
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subunit in E.Coli polymerase that is required for recognition of the transcription to start is
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sigma
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Aminoacyl-tRNA synthase catalyses
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attachment of a particular amino acid to a particular tRNA
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a group of ribosomes translating the same mRNA are called?
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Polysome or polyribosome
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why is the genetic code described as redundant?
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most amino acids are specified by more than one codon
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protein synthesis in bacterial cells usually starts with a
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formylmethionine residue
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how many different reading frames are possible
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3
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pH 7, generic amino acids is a zwitterion
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both NH3+ and COO-, neutral charge
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4 types of noncovalent bonds that form between the atoms of a polypeptide's backbone and the atoms of it side chain
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electrostatic interaction
van der waals hydrogen bonding hydrophobic interactions |
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what type of bond doesn't determine secondary and higher order structures
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peptide bonds
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for a typical enzyme, the __________ amino acids are located in the interior of the protein, while the _______ amino acids are located on the exterior.
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hydrophobic; hydrophilic
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the highest level of organization in a fibrous protein is _______ structure and in a globular protein with one polypeptide is _________ structure
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Quaternary; tertiary
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2 mechanisms that regulate activity of enzyme
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phosphorylation
binding to other molecules |
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Restriction enzymes
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1. are Endonucleases, endoDNases
2. Digest double-stranded DNA at internal phosphodiester bonds 3, Cut DNA at specific sites • defined by nucleotide sequences • restriction sites or restriction sequences • palindromes • 4-8 nucleotides 3. Leave 3’-hydroxyl and 5’-phosphate groups on both strands can be either Blunt ends or Sticky or cohesive ends • 5’-overhangs • 3’-overhangs |
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The enzyme DNA _______ requires _____ to covalently link DNA fragments together
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Ligase;ATP
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3 main feautres of a plasmid vector that facilitate cloning of a DNA fragment are?
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1. an origin of replication, so that the plasmid can be replicated
2. an antibiotic resistance gene to allow selection of transformed host cells 3. often, a 'polylinker' containing several different restriction enzyme recognition sites and a second marker gene |
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why do individual DNA fragments separate from each other during agarose gel electrophoresis?
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the DNA moves along the gel towards the positive charge, shorter fragments move further along
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what is the target molecule on a southern blot, and the uses of southern hybridisation
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DNA,
• identify related genes • determine number of related genes • determine size(s) of related genes • construction of restriction maps |
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what is the target molecule on a northern blot, and the uses of northern hybridisation
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RNA
• identify related transcripts • determine number of related transcripts • determine size(s) of related transcripts • determine patterns of gene expression, |
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what hybridisation technique would you use to determine which cells expressed the gene?
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in situ
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In situ
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Use
approximate mapping of genes directly on chromosomes Procedure cells & nuclei broken open chromosomes spread on microscope slide chromosome DNA denatured labelled with fluorescent tagged-probe |
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in solution a double stranded DNA molecule will denature when the _____, resulting in the disruption of ______________
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Temperature is high, phosphodiester bonds
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Anti sense probe
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• sequence is complementary to
transcript |
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homologous
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homologous: to detect identical
nucleic acid molecules |
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heterologous
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heterologous: to detect related
molecules |
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3 steps in PCR
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Step one- Heat to separate (denaturation)
Step two- hybridization of primers (annealing) Step three- DNA synthesis from primers (elongation) |
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three components of PCR
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1. double stranded DNA (primer)
2. DNA polymerase 3. four different deoxyribonucleotide triphosphates |
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All of the following are true for reverse transcriptase except
a. it is an RNA-dependent DNA polymerase b. It is an RNA- dependent RNA polymerase c. it requires a primer for activity d. it synthesizes a new nucleic acid strand in a 5' to 3' direction e. combined with the polymerase chain reaction it can be used to examine gene expression |
B. it is a RNA- directed RNA polymerase
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What Covalent Interaction Stabilises Protein
Conformations? |
disulphide bonds
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Which of the following shows the usual order of steps for cloning a DNA
fragment? A. restriction enzyme digestion, bacterial cell transformation, growth of bacterial cells, ligation with DNA ligase B. restriction enzyme digestion, growth of bacterial cells, bacterial cell transformation, ligation with DNA ligase C. restriction enzyme digestion, ligation with DNA ligase, bacterial cell transformation, growth of bacterial cells D. restriction enzyme digestion, ligation with DNA ligase, growth of bacterial cells, bacterial cell transformation |
C. restriction enzyme digestion, ligation with DNA ligase, bacterial cell
transformation, growth of bacterial cells |
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single RNA molecule that is translates into a number of different proteins is called
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polycistronic mRNA
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For biosynthetic pathways the regulatory molecule is often?
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the final end product of the pathway
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what are the four ways that cells can control gene expression
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1. transcriptional control
2. RNA processing control 3. translational control 4. post-translational control |
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3 principles of control
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1. coordinate regulation (x->Y)
2. degrative (catabolic) (xyz-> x) 3. biosynthetic (anabolic) (x->xyz) |
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tryptophan operon in e coli
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contains an operator region with the promoter sequence
none of it, switched on. have it switched off |
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the two proteins needed for lactose metabolism
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galactoside permease & B- galactosidase
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the inducer of the lactose operon in E.coli is
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lactose
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During negative regulation of the lac operon
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the inducer binds to the repressor
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gene encoding galactoside permease is called
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y gene
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lactose operon is
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both positive and negative transcriptional control
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regulatory DNA binding proteins of prokaryotes include
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CAP activator
Lac repressor Trp repressor |
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when both glucose and lactose are present in E.coli
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the CAP activator protein is not bound
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what is the activator CAP
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both cyclic CMP (cCMP) and CAP
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the points of differentiation
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1. often marked by a change in cell morphology
2. differentiated cells produce specific proteins 3. differentiation is usually preceded by rapid proliferation 4. it involves a change in the cells DNA that normally occurs without errors |
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chromosome =
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DNA and protein(histome)
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what modification neutralizes the charges on histones
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acetylation
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what is the name given to the protein that control gene transcription and bind to regulatory elements of DNA and how are they categorized
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known as transcription factors, either general or cell tissue specific
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what is a spliceosome
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elaborate complex of proteins and small nuclear RNA, it does the splicing, removing of introns
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what sort of control elements regulate transcription
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cis-acting control elements
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what part of mRNA does degradation generally begin
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the 3' end with removal of poly a tail
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features of capseses
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1. aspartate-specific proteases
2. they are normally found as inactive zymogens 3. target other proteins for destruction |
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meiosis I is called _______ division and meiosis II is called _______ division
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reduction; equational
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crossing over and the random distribution of maternal and paternal chromosomes is responsible for?
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genetic variation
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proteins known as ______ appear at different times in the cell cycle, and their expression is controlled at the level of _______. these proteins control the activity of ________ proteins, which in turn _________ target proteins tethered by _______
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Cyclins; transcription; Cdk, Phosphorylate; cyclins
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cell cycle check point ensures
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1. spindles are properly formed and chromosomes are attached
2. chromosomes are present, critical stages of cell cycle completed 3. cellular environment favourable 4. entry into s or m is prevented if DNA is damaged |
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what are the three check points
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1. r-restriction point (G1)
2. s-phase checkpoint (G2) 3. mitosis (metaphase) |
