protein Quiz 2 Flashcards
(25 cards)
Who discovered DNA and when?
Friedrich Miescher in 1869, from white blood cells.
What is the Central Dogma of molecular biology?
DNA → RNA → Protein
What are the components of a nucleotide?
A five-carbon sugar, phosphate group, and nitrogenous base.
Name the purines and pyrimidines in nucleic acids.
Purines: A, G; Pyrimidines: C, T (DNA), U (RNA)
What is a nucleoside?
A nitrogenous base attached to a sugar (no phosphate).
What bonds hold DNA nucleotides together?
3’–5’ phosphodiester bonds.
What type of bonding holds DNA strands together?
Hydrogen bonding between complementary base pairs.
Describe the DNA double helix.
Two antiparallel strands forming a right-handed helix.
How many hydrogen bonds form between A-T and G-C pairs?
A-T has 2; G-C has 3.
What is B-DNA?
The most common DNA form: right-handed helix with ~10.4 bp per turn.
What are nucleosomes?
DNA (~200 bp) wrapped around histone octamers (H2A, H2B, H3, H4).
What are the 4 main forces stabilizing DNA structure?
Stacking interactions, hydrogen bonds, hydrophobic effects, charge-charge interactions.
What is DNA denaturation and what affects its Tm?
Unwinding of DNA strands; GC-rich DNA has higher Tm.
What is chromatin?
DNA packaged with proteins (like histones) in eukaryotic cells.
What type of RNA is most abundant in the cell?
rRNA (~80% of total RNA).
What is transcription?
The process of copying DNA into RNA.
Where does transcription occur in eukaryotes vs prokaryotes?
Eukaryotes: nucleus; Prokaryotes: cytoplasm.
What enzyme synthesizes RNA from DNA?
RNA polymerase.
What is a promoter?
A DNA sequence where RNA polymerase binds to start transcription.
What is an operon and where is it found?
A group of genes under one promoter, found in prokaryotes.
What are the three stages of transcription?
Initiation, Elongation, Termination.
What are rho-dependent and rho-independent termination?
Rho-dependent requires rho protein; rho-independent relies on GC-rich hairpin loops.
Name the three eukaryotic RNA polymerases and their products.
Pol I: rRNA; Pol II: mRNA/snRNA; Pol III: tRNA/other small RNAs.
What are enhancers and silencers?
Cis-acting DNA sequences that increase or decrease gene transcription.
