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Questions and Answers
What is the primary role of DNA polymerase during DNA replication?
What is the primary role of DNA polymerase during DNA replication?
- To synthesize RNA from the DNA template
- To add new complementary nucleotide bases to the DNA strand (correct)
- To unwind the DNA double helix
- To remove primer sequences from the DNA
How do Okazaki fragments form during DNA replication?
How do Okazaki fragments form during DNA replication?
- By the action of RNA polymerase
- By the action of helicase on the DNA template
- By short, newly synthesized stretches of DNA on the lagging strand (correct)
- By continuous synthesis on the leading strand
What distinguishes transcription from DNA replication?
What distinguishes transcription from DNA replication?
- Transcription creates a permanent RNA strand
- DNA replication involves multiple polymerases
- RNA strands are not permanently bonded to their DNA template (correct)
- Transcription involves helicase activity
What enzyme is responsible for catalyzing the removal of primer sequences during DNA replication?
What enzyme is responsible for catalyzing the removal of primer sequences during DNA replication?
What is the significance of the genetic code being described as degenerate?
What is the significance of the genetic code being described as degenerate?
Which molecular chaperone system is primarily involved in protein folding, refolding, and degradation?
Which molecular chaperone system is primarily involved in protein folding, refolding, and degradation?
What role do transcription factors play in gene expression?
What role do transcription factors play in gene expression?
How are BAG1 and BAG3 related to the function of HSP70?
How are BAG1 and BAG3 related to the function of HSP70?
What is the primary role of the TATA box in transcription?
What is the primary role of the TATA box in transcription?
Which enzyme is primarily responsible for catalyzing transcription?
Which enzyme is primarily responsible for catalyzing transcription?
What is the significance of the promoter region in transcription?
What is the significance of the promoter region in transcription?
During transcription elongation, in which direction are nucleotides incorporated into the growing RNA strand?
During transcription elongation, in which direction are nucleotides incorporated into the growing RNA strand?
What is the role of introns in pre-mRNA?
What is the role of introns in pre-mRNA?
What process involves the addition of a poly(A) tail to pre-mRNA?
What process involves the addition of a poly(A) tail to pre-mRNA?
What molecules mediate the binding of RNA polymerase to DNA in eukaryotic transcription initiation?
What molecules mediate the binding of RNA polymerase to DNA in eukaryotic transcription initiation?
Where does translation take place within a eukaryotic cell?
Where does translation take place within a eukaryotic cell?
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Study Notes
Central Dogma of Molecular Biology
- Flow of genetic information is from DNA to RNA to protein.
- DNA replication produces exact copies of DNA.
DNA Replication
- Helicase unzips the DNA double helix during replication.
- DNA polymerase adds complementary nucleotide bases to form new DNA strands.
- DNA strands orient in two directions: 3' to 5' (leading strand) and 5' to 3' (lagging strand).
- Okazaki fragments are short DNA segments synthesized on the lagging strand.
- Exonuclease removes primer sequences during replication.
- Resulting in two DNA molecules, each containing one old and one new nucleotide chain.
Transcription
- Involves copying DNA information into mRNA.
- RNA polymerase is the enzyme responsible for transcription.
- RNA strands are not permanently bonded to the DNA template.
- Eukaryotes have three classes of polymerases: Pol I, Pol II, Pol III.
- RNA is shorter than DNA since it is transcribed from limited regions.
Genetic Code
- Degenerate or redundant nature allows one amino acid to be coded by multiple codons.
- Cells read DNA code in triplets, groups of three bases.
Molecular Chaperones
- Two types: HSP60 and HSP70, assist in polypeptide chain folding.
- Chaperones prevent protein aggregation by recognizing exposed hydrophobic regions.
- Misfolded proteins are tagged for degradation by ubiquitin ligase, leading to proteasomal degradation.
- HSP70 chaperone system manages protein folding, refolding, and degradation through an ATP-consuming mechanism.
- Co-chaperones (HSP40, HIP, CHIP) regulate HSP70 activity and facilitate processes.
Transcription Factors
- Bind to enhancer and promoter sequences to recruit RNA polymerase.
- Promoter regions signal the transcription starting point and direction.
- Initiation bubble forms to allow RNA polymerase access to the DNA strand.
- TATA box: a conserved sequence crucial for initiating transcription in eukaryotes.
mRNA Processing
- mRNA undergoes several processing steps:
- Introns (non-coding sections) are spliced out during RNA splicing.
- A 5' cap is added to protect RNA and facilitate ribosome recognition.
- Polyadenylation adds a poly(A) tail to enhance RNA stability.
Translation
- Involves converting mRNA into proteins.
- Takes place in the cytoplasm on ribosomes.
- tRNA molecules serve as adaptors, reading mRNA codons and attaching specific amino acids.
- rRNA acts as the catalytic component of ribosomes.
Open Reading Frame (ORF)
- Refers to the portion of mature mRNA that is translated into protein.
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