p.5
DNA Structure and Function
What are the components of a nucleotide?
A phosphate group, a sugar, and a nitrogenous base.
p.15
Gene Regulation and Expression
What happens to the DNA generated from retroviral RNA?
It can be inserted into the genome of the host cell and expressed.
p.9
DNA Replication Mechanisms
What is the function of enzymes during DNA replication?
They unwind the parental strands and correct errors.
p.1
Gene Expression Overview
What are the two steps required for gene expression?
Transcription and translation.
p.6
RNA Structure and Types
What is the structure at the 5' end of eukaryotic mRNA?
A cap structure consisting of methylated guanine triphosphate.
p.1
Gene Expression Overview
Where is genetic information mainly located in eukaryotes?
In the nuclei, with small amounts in mitochondria.
What can mutations in DNA lead to?
Genetic alterations, including abnormal cell growth and cancer.
p.9
Gene Regulation and Expression
What happens during the G1 phase of the cell cycle?
Cells prepare to duplicate their chromosomes.
p.5
DNA Structure and Function
Which nitrogenous bases are found in DNA?
Adenine, Thymine, Cytosine, and Guanine.
How is DNA damage repaired?
By removing and replacing the damaged region using the intact strand as a template.
p.7
Translation Process and Genetic Code
How many types of cytosolic rRNA are present in eukaryotes?
Four types: 18S, 28S, 5S, and 5.8S rRNA.
p.4
DNA Structure and Function
What is renaturation in the context of DNA?
Renaturation is the process where separated DNA strands re-form base pairs when the temperature is slowly decreased.
p.8
Translation Process and Genetic Code
What are the ribosome subunits in prokaryotes?
70S ribosome composed of 50S and 30S subunits, with 5S, 23S, 16S rRNA and 34 proteins.
What condition is particularly pronounced in individuals with xeroderma pigmentosum (XP)?
Their DNA repair system does not function properly, leading to increased skin cancer risk.
p.2
DNA Structure and Function
How do the two chains of DNA run?
Antiparallel; one runs 5′ to 3′ and the other runs 3′ to 5′.
p.20
Translation Process and Genetic Code
What determines the sequence of amino acids in a protein during translation?
The sequence of codons in mRNA.
p.15
Gene Regulation and Expression
What role does reverse transcriptase play in transposons?
It synthesizes DNA copies of the transposon, which can integrate into the genome.
What are the major causes of cancer?
Radiation, chemicals, and viruses.
How do radiation and chemicals lead to cancer?
They cause damage to DNA, which can produce mutations if not repaired rapidly.
p.6
RNA Structure and Types
What is the role of rRNA in ribosomes?
It associates with proteins to form ribosomes.
p.6
RNA Structure and Types
What enzymatic activity does peptidyl transferase have?
It is an enzyme in protein synthesis that consists of RNA.
p.17
Transcription Process in Eukaryotes
What is the consensus sequence found in bacterial promoters?
tA tAA t (Pribnow box) and TTGACA, located about 10 and 35 bases upstream from the transcription start point, respectively.
p.2
DNA Structure and Function
What is chromatin?
The protein-DNA complexes found on chromosomes within the nucleus.
p.17
Translation Process and Genetic Code
What is a polycistronic mRNA?
An mRNA that produces several different proteins during translation, one from each cistron.
p.2
RNA Structure and Types
What is the role of mRNA's cap and poly(A) tail?
The cap is at the 5′ end and the poly(A) tail is at the 3′ end, aiding in stability and translation.
p.10
DNA Replication Mechanisms
What role do helicases play in DNA replication?
They unwind the DNA helix.
p.10
DNA Replication Mechanisms
What is the function of topoisomerases during DNA replication?
They prevent extreme supercoiling of the parental helix.
p.19
Transcription Process in Eukaryotes
What happens to primary transcripts for tRNA?
They are cleaved at the 5′ and 3′ ends.
p.19
Transcription Process in Eukaryotes
What is the function of nucleotidyl transferase in tRNA processing?
It catalyzes the addition of the sequence ccA to the 3′ end.
p.20
Translation Process and Genetic Code
What is meant by the genetic code being nonoverlapping?
Each nucleotide is used only once, starting with a start codon and ending with a stop codon.
p.6
RNA Structure and Types
What is the function of RNase P?
It cleaves tRNA precursors.
p.2
DNA Structure and Function
What are the monomeric units of nucleic acids?
Nucleotides, which contain a nitrogenous base, a sugar, and phosphate.
p.2
DNA Structure and Function
What bases are found in DNA?
Adenine (A), guanine (G), cytosine (C), and thymine (T).
p.4
DNA Structure and Function
How many base pairs does the chromosome of Escherichia coli contain?
More than 4 × 10^6 base pairs.
p.13
DNA Replication Mechanisms
How does the leading strand differ from the lagging strand during DNA replication?
The leading strand is synthesized continuously, while the lagging strand is synthesized discontinuously.
p.17
Transcription Process in Eukaryotes
What is the role of ribonucleoside triphosphates in RNA synthesis?
They serve as precursors for the RNA chain.
p.11
DNA Replication Mechanisms
What is the function of helicases in DNA replication?
They separate parental DNA strands by unwinding the double helix.
What is hereditary nonpolyposis colorectal cancer (HNPCC) associated with?
Defective mismatch repair.
p.11
DNA Replication Mechanisms
What is the role of topoisomerases in DNA replication?
They relieve torsional strain on the parental duplex caused by unwinding.
p.10
DNA Replication Mechanisms
What are replication forks?
Sites at which DNA synthesis is occurring.
p.20
Translation Process and Genetic Code
What role does tRNA play in protein synthesis?
tRNA carries amino acids to the ribosomal site of protein synthesis.
p.20
Translation Process and Genetic Code
What is the start codon for polypeptide chain initiation?
Methionine (codon = AUG).
p.10
DNA Replication Mechanisms
What is the role of DNA gyrase?
It is a topoisomerase found only in prokaryotes, inhibited by quinolone antibiotics.
p.16
Transcription Process in Eukaryotes
What is the difference between RNA polymerase I and RNA polymerase III?
RNA polymerase I produces rRNA, while RNA polymerase III produces tRNA and 5S rRNA.
p.5
Gene Regulation and Expression
What is the primary function of transcription in gene expression?
To synthesize RNA from a DNA template.
p.3
RNA Structure and Types
Which nitrogenous bases are classified as purines?
Adenine (A) and Guanine (G).
p.7
Gene Expression Overview
What is the role of histone H1 in chromatin structure?
Histone H1 helps in the formation of the solenoid structure.
p.7
Transcription Process in Eukaryotes
What is the structure of eukaryotic mRNA's cap?
It includes a methylguanosine triphosphate linkage.
p.1
Translation Process and Genetic Code
What roles do ribosomal RNA (rRNA) and transfer RNA (tRNA) play?
They participate in the process of translation.
p.7
Translation Process and Genetic Code
What are some modified nucleotides found in eukaryotic tRNA?
Pseudouridine (ψ), dihydrouridine (d), and ribothymidine (t).
p.13
DNA Replication Mechanisms
What are Okazaki fragments?
Short fragments formed during the discontinuous copying of the lagging strand.
p.17
Transcription Process in Eukaryotes
What is the direction of DNA template copying during transcription?
3' to 5' direction, while the RNA chain grows in the 5' to 3' direction.
p.11
DNA Replication Mechanisms
What are the precursors for DNA synthesis?
Deoxyribonucleoside triphosphates (dATP, dGTP, dTTP, and dCTP).
p.20
Translation Process and Genetic Code
Where does translation occur in eukaryotic cells?
In the cytoplasm, on ribosomes.
p.10
DNA Replication Mechanisms
What does it mean for DNA replication to be semiconservative?
Each daughter molecule contains one intact parental strand and one newly synthesized strand.
p.13
DNA Replication Mechanisms
What is the direction of synthesis for the lagging strand?
3' to 5' away from the replication fork.
How can proto-oncogenes lead to cancer?
If altered or expressed abnormally, they can result in cancer.
p.20
Translation Process and Genetic Code
In which direction is a protein synthesized?
From the N-terminus to the C-terminus, following the 5' to 3' direction of mRNA.
What is the function of microRNAs (miRNAs) in cancer?
They can act as either oncogenes or tumor suppressors depending on the genes they regulate.
p.20
Translation Process and Genetic Code
What does it mean that the genetic code is degenerate?
Each of the 20 common amino acids has at least one codon, and many have multiple codons.
p.16
Transcription Process in Eukaryotes
What is the primary product of transcription in eukaryotes?
A modified and trimmed RNA molecule.
p.18
Transcription Process in Eukaryotes
What is the first RNA form produced from a eukaryotic gene?
Heterogeneous nuclear RNA (hnRNA).
p.3
RNA Structure and Types
What distinguishes ribose from deoxyribose?
Ribose has a hydroxyl group on carbon two, while deoxyribose does not.
p.13
DNA Replication Mechanisms
What is the first step in DNA synthesis at the replication fork?
Unwinding of parental strands.
p.8
Translation Process and Genetic Code
What are the ribosome subunits in eukaryotes?
80S ribosome composed of 60S and 40S subunits, with 5S, 28S, 18S, 5.8S rRNA and 83 proteins.
p.8
RNA Structure and Types
What is the structure of tRNA molecules?
tRNA molecules have a cloverleaf structure.
p.1
Translation Process and Genetic Code
Why is understanding protein synthesis important?
It helps in understanding antibiotics that target prokaryotic protein synthesis and toxins.
p.14
DNA Repair Mechanisms
What is nucleotide excision repair?
Removal of a group of nucleotides, including the damaged one, from a DNA strand.
p.4
RNA Structure and Types
What is the significance of extensive base-pairing in RNA?
It produces secondary and tertiary structures that are important for RNA function.
p.13
DNA Replication Mechanisms
How many ribonucleotides are polymerized on the lagging strand in eukaryotes?
About 10 ribonucleotides.
p.10
DNA Replication Mechanisms
What are the three DNA polymerases found in prokaryotes?
Pol I, Pol II, and Pol III.
What can the movement of antibiotic resistance genes between plasmids and host chromosomes lead to?
Multidrug-resistant bacteria.
p.16
Transcription Process in Eukaryotes
What is the role of RNA polymerase in transcription?
It catalyzes the synthesis of RNA from a DNA template.
p.3
RNA Structure and Types
Which nitrogenous bases are classified as pyrimidines?
Cytosine (C), Thymine (T), and Uracil (U).
p.18
Transcription Process in Eukaryotes
What are exons?
Sequences within a transcript that appear in the mature mRNA.
p.9
Recombinant DNA Technology
What does it mean for DNA molecules to recombine?
A portion of a strand from one molecule can be exchanged for a portion of a strand from another molecule.
p.9
Gene Regulation and Expression
What is transposition in genetics?
The movement of genes from one chromosomal site to another.
p.18
Gene Regulation and Expression
What is the role of enhancers in transcription?
Enhancers are DNA sequences that stimulate the transcription rate.
p.2
DNA Structure and Function
What sugar is present in DNA and RNA?
DNA contains deoxyribose, while RNA contains ribose.
p.4
DNA Structure and Function
Where is DNA located in prokaryotic cells?
In the cytoplasm of the cell.
p.4
DNA Structure and Function
What is the structure of chromatin in eukaryotic cells?
Chromatin consists of DNA complexed with histones in nucleosomes.
p.4
DNA Structure and Function
What are histones?
Histones are small, basic proteins with a high content of arginine and lysine that help package DNA.
p.17
Transcription Process in Eukaryotes
What is the function of the sigma factor in E. coli RNA polymerase?
It is required for the initiation of RNA synthesis.
p.1
Recombinant DNA Technology
What is important for the future of diagnostic medicine?
The use of recombinant DNA technology for testing and diagnosis of specific diseases.
p.19
Translation Process and Genetic Code
What forms the 40S ribosomal subunit?
18S rRNA complexes with proteins.
p.11
DNA Replication Mechanisms
What is the function of DNA ligase in DNA replication?
It joins two adjacent DNA strands by forming a phosphodiester bond.
p.12
DNA Replication Mechanisms
What is produced when pyrophosphate is cleaved?
Two inorganic phosphates.
p.20
Translation Process and Genetic Code
What signals the termination of polypeptide synthesis?
A termination codon (UGA, UAG, or UAA).
p.20
Translation Process and Genetic Code
What is a codon?
A sequence of three nucleotides in mRNA that specifies a particular amino acid.
p.20
Translation Process and Genetic Code
What does commaless mean in the context of the genetic code?
There are no breaks or markers to distinguish one codon from the next.
p.5
Translation Process and Genetic Code
What is the role of translation in protein synthesis?
To synthesize proteins from mRNA.
p.15
Gene Regulation and Expression
What is reverse transcription?
Synthesis of DNA from an RNA template, catalyzed by reverse transcriptase.
p.6
DNA Structure and Function
What direction do the antiparallel strands of DNA run?
In opposite directions, determined by the hydroxyl groups on carbons 3 and 5 of the deoxyribose.
p.5
DNA Structure and Function
What is the significance of base pairing in DNA?
It ensures accurate replication and transcription.
p.17
Transcription Process in Eukaryotes
What unusual modification occurs in mature tRNA?
Posttranscriptional modification of normal nucleotides and the addition of a CCA sequence at the 3' end.
p.17
Transcription Process in Eukaryotes
How does eukaryotic RNA travel for translation?
It must travel from the nucleus to the cytoplasm.
p.11
DNA Replication Mechanisms
What is the role of DNA polymerase δ during replication?
It acts as the lead polymerase on the lagging strand.
p.2
DNA Structure and Function
How are polynucleotides formed?
By nucleosides joined by 3′,5′-phosphodiester bridges.
p.8
RNA Structure and Types
What is the role of the cc A sequence at the 3' end of tRNA?
It carries the amino acid.
p.19
Translation Process and Genetic Code
Which rRNAs form the 60S ribosomal subunit?
28S, 5.8S, and 5S rRNAs complex with proteins.
p.13
DNA Replication Mechanisms
How many deoxyribonucleotides are polymerized on the lagging strand in eukaryotes?
About 200 deoxyribonucleotides.
How does methotrexate affect DNA synthesis?
It inhibits the formation of tetrahydrofolate, affecting thymine and purine synthesis.
p.9
Translation Process and Genetic Code
What is the role of tRNA in protein synthesis?
tRNA carries amino acids to the ribosome and matches them to the codons in mRNA.
p.9
Gene Regulation and Expression
What occurs during the S phase of the cell cycle?
Synthesis of DNA (replication) occurs.
p.6
RNA Structure and Types
What are ribozymes?
RNA molecules that act as catalysts, removing internal segments of themselves and splicing the ends together.
p.18
Transcription Process in Eukaryotes
What are introns?
Sequences within the primary transcript that are removed and do not appear in the mature mRNA.
p.11
DNA Replication Mechanisms
What is the direction of DNA synthesis during replication?
DNA synthesis occurs in the 5' to 3' direction.
p.1
Gene Expression Overview
What determines the structure and function of cells?
Proteins, the products of genes.
p.1
Recombinant DNA Technology
What is recombinant DNA technology used for?
To study and manipulate genes, and for diagnostics.
p.13
DNA Replication Mechanisms
What is the role of RNA primers in DNA synthesis?
They initiate the synthesis of new DNA strands.
p.19
Gene Regulation and Expression
What do repressors do in the transcription process?
Repressors bind and inhibit transcription.
p.13
DNA Replication Mechanisms
What is the direction of synthesis for the leading strand?
3' to 5' toward the replication fork.
p.17
Transcription Process in Eukaryotes
What is the role of RNase P in tRNA synthesis?
It cleaves larger transcripts to produce tRNA and contains an RNA molecule that acts as a catalyst.
p.17
Transcription Process in Eukaryotes
What conserved sequences are found in eukaryotic basal promoter regions?
The TATA box (Hogness box) and the CAAT box.
What happens when suppressor genes like p53 are decreased?
Increased cell growth occurs.
p.12
DNA Replication Mechanisms
What is the role of DNA primase in DNA replication?
It catalyzes the formation of the RNA primer.
p.16
Transcription Process in Eukaryotes
What modifications occur to eukaryotic mRNA after transcription?
It is capped at the 5' end, has a poly(A) tail added at the 3' end, and introns are removed.
p.15
Gene Regulation and Expression
How does retroviral RNA contribute to DNA synthesis?
It serves as a template for the synthesis of DNA by reverse transcriptase.
p.4
RNA Structure and Types
What are the main components of nucleotides?
Nucleotides consist of a base, a sugar, and a phosphate group.
p.4
RNA Structure and Types
What distinguishes the carbon numbering in sugars from bases in nucleotides?
The prime symbol is used for carbon numbers in sugars, while bases do not use the prime symbol.
p.17
Transcription Process in Eukaryotes
What is the difference in transcription and translation between bacteria and eukaryotes?
In bacteria, transcription and translation occur simultaneously; eukaryotic RNA must exit the nucleus for translation.
p.18
Transcription Process in Eukaryotes
What is the significance of the poly(A) tail in hnRNA?
It serves as a signal for the cleavage of hnRNA and addition of the poly(A) tail by poly(A) polymerase.
p.18
Transcription Process in Eukaryotes
What is the splice point sequence at the 5' end of an intron?
GU, preceded by an invariant AG at the 3' end of the adjacent exon.
p.10
DNA Replication Mechanisms
What is the nature of DNA replication in eukaryotic chromosomes?
Replication is bidirectional and semiconservative.
p.13
DNA Replication Mechanisms
What happens to RNA primers after DNA synthesis?
They are removed by nucleases and gaps are filled with deoxyribonucleotides.
p.8
RNA Structure and Types
What does the t ψ c loop in tRNA contain?
Ribothymidine and pseudouridine.
What are the types of mutations that can occur in DNA?
Point mutations, insertions, and deletions.
p.4
RNA Structure and Types
What base pairs with uracil in RNA?
Adenine pairs with uracil.
What is the significance of the bcr-abl protein in chronic myelogenous leukemia (CML)?
It is created by a translocation between chromosomes 9 and 22 and is targeted by the drug Gleevec.
p.19
Transcription Process in Eukaryotes
What is the significance of posttranscriptional modification in tRNA?
It includes the conversion of uridine to pseudouridine, ribothymidine, and dihydrouridine.
What is Rifampicin used for?
It inhibits the initiation of prokaryotic RNA synthesis and is used to treat tuberculosis.
p.5
DNA Structure and Function
What does the presence of thymine indicate about a nucleic acid?
It indicates that the nucleic acid is DNA.
p.18
Transcription Process in Eukaryotes
What modifications are made to hnRNA before it becomes mature mRNA?
A 5' cap is added and a poly(A) tail is added to the 3' end.
p.1
Gene Regulation and Expression
How is gene expression regulated?
By a variety of mechanisms, with only a small fraction of the genome expressed in any one cell.
p.7
Translation Process and Genetic Code
How do mitochondrial ribosomes compare to prokaryotic ribosomes?
Mitochondrial ribosomes are similar to prokaryotic ribosomes.
p.19
Gene Regulation and Expression
What is the role of activators in transcription?
Activators bind and stimulate transcription.
p.8
RNA Structure and Types
What is found in the middle loop of tRNA?
The anticodon, which base-pairs with the codon in mRNA.
p.11
DNA Replication Mechanisms
What do single-strand binding proteins do during DNA replication?
They prevent single strands of DNA from reassociating.
p.19
Transcription Process in Eukaryotes
What modifications occur to the 45S precursor?
It undergoes methylation and cleavages to produce 18S rRNA and 28S rRNA.
p.2
DNA Structure and Function
What causes DNA denaturation?
Alkali or heat, which separate the strands without breaking phosphodiester bonds.
p.8
DNA Replication Mechanisms
In which direction does DNA polymerase synthesize the new strand?
In the 5' to 3' direction.
p.14
Recombinant DNA Technology
What are transposons?
Mobile genetic elements that facilitate the movement of genes.
What is the mechanism of action of 5-fluorouracil (5-FU)?
It prevents the conversion of dUMP to dTMP, reducing thymine nucleotides for DNA synthesis.
p.6
RNA Structure and Types
What does the poly(A) tail of eukaryotic mRNA consist of?
Up to 200 adenine (A) nucleotides attached to the hydroxyl group at the 3' end.
p.4
DNA Structure and Function
What is hybridization in molecular biology?
Hybridization is when a single strand of DNA pairs with complementary base sequences on another strand of DNA or RNA.
p.18
Transcription Process in Eukaryotes
What are small nuclear RNAs (snRNPs) involved in?
They are involved in the cleavage and splicing process of hnRNA.
p.18
Gene Regulation and Expression
What is the function of the TATA box in eukaryotic promoters?
It is a historical element included in the promoter region, though only 12.5% of eukaryotic promoters contain this sequence.
p.14
DNA Repair Mechanisms
What proofreading function is associated with the polymerase complex during DNA replication?
3' to 5' exonuclease activity.
p.4
RNA Structure and Types
How does RNA differ from DNA?
RNA contains ribose instead of deoxyribose and uracil instead of thymine, and is generally single-stranded.
p.2
RNA Structure and Types
What is the structure of tRNA?
It forms a cloverleaf structure that contains unusual nucleotides and an anticodon.
p.20
Translation Process and Genetic Code
What is a polysome?
A structure formed when many ribosomes attach simultaneously to a single mRNA molecule.
p.14
DNA Repair Mechanisms
What is the role of glycosylase in base excision repair?
It removes a damaged base by hydrolyzing an N-glycosidic bond.
p.14
DNA Repair Mechanisms
How does mismatch repair work in bacteria?
It removes the newly synthesized strand that contains mismatched bases, as it has not yet been methylated.
p.20
Translation Process and Genetic Code
Where are membrane-bound and secreted proteins synthesized?
On the rough endoplasmic reticulum (RER).
What is the effect of α-amanitin?
It inhibits eukaryotic RNA polymerases, particularly polymerase II, and can be lethal.
What defect is associated with Bloom syndrome?
A defect in a helicase necessary to unwind DNA strands during replication.
What is the role of oncogenes?
Oncogenes are genes that cause cancer.
p.14
DNA Repair Mechanisms
What is transcription-coupled repair?
Repair that occurs when the transcription apparatus detects DNA damage in the gene being transcribed.
p.12
DNA Repair Mechanisms
What is the function of bypass polymerases?
To bypass areas of DNA damage during replication.
