Molecular Biology Review (Lecture 5) Flashcards
What are the goals of viruses and how do they achieve that?
replicate its genome and assemble new progeny by taking over host cell’s cellular processes and have it focus on the virus’s goals
What does it mean that cellular processes are localized?
there is a specific place where only these processes (DNA replication, transcription, translation) can occur
In which direction is DNA read and then synthesized?
read 3’-5’ and synthesized 5’-3’ (bottom strand = leading)
What type of bond are between nucleotides?
phosphodiester bond
What are non-coding RNAs?
tRNAs and rRNA types of RNA
What are enhancer proteins?
help the transcription of the genes
Which type of polymerase binds to promoter sequences on the DNA?
DNA-dependent RNA polymerase
How much of our genes are actually made into proteins?
1.5%
What is the enzyme that replicates DNA?
DNA-dependent DNA polymerase
Where does the DdDp bind to on the DNA?
origin of replication (ORI)
What enzyme puts down the RNA primer needed for DNA replication?
DNA-dependent RNA polymerase
Which enzyme binds to DNA right after the DdDp sits on the DNA? And why?
helicase to unwind the DNA
What are the 3 important properties of DNA-dependent DNA polymerase?
requires RNA primer, high fidelity of copying (resistant to error), proofreading ability
What is the proofreading ability of DdDp attributed to?
exonuclease activity 3’-5’
Why does DdDp need an RNA primer?
cannot initiate de novo synthesis because DNA nucleotides don’t have a free 3’OH group
What does “de novo” mean?
synthesize on its own, “from new”
What is the enzyme needed for transcription?
DNA-dependent RNA polymerase
What are the 4 important properties of DNA-dependent RNA polymerase?
binds to the promoter region of DNA, built-in helicase activity, de novo synthesis of RNA, NO proofreading ability
What is the difference between preliminary mRNA and mature mRNA?
depending if it had gone through the 3 necessary modifications
What are the necessary 3 modifications of preliminary mRNA in order for it to leave the nucleus?
5’ cap, poly (A) tail, and RNA splicing
What are the 3 important reasons why mRNA needs a 5’ cap?
help mRNA get out of nucleus, prevent it from degradation of RNases, translation initiation complex recognizes 5’ cap to start translation
What is the “Initiation” step of translation?
initiation complex forms when it recognizes the 5’ cap
What makes up the initiation complex?
small subunit and tRNA molecule that recognizes the start codon –> large subunit goes on top of it
What step in translation is the key step for viruses?
initiation since the viruses need to get their transcripts recognized by the host cell translation machinery
What is the difference between monocistronic and polycistronic?
monocistronic transcripts can code for ONLY ONE protein /polypeptide | polycistronic transcripts can code for MORE THAN ONE different protein off of the same transcript
Which organisms have monocistronic transcripts?
eukaryotes
Which organisms have polycistronic transcripts?
prokaryotes and viruses
Which type of transcripts do eukaryotic translation machinery only recognize?
monocistronic
What is the role of the ER?
protein folding, packaging, and some modification
What is the role of the Golgi?
modification of proteins and transport them out
What is the exocytic pathway?
proteins that get secreted by the cell
Where does the Golgi direct proteins when they need to be degraded?
lysosome
What are the 3 endocytic pathways?
phagocytosis, pinocytosis, and receptor-mediated endocytosis
What is phagocytosis?
“cell eating”; constantly taking in molecules from the environment; ex of phagocytic cell = immunological cells
What is pinocytosis?
cell-drinking, taking up fluids
What cytoskeleton element mediates phagocytosis and pinocytosis and why?
actin because these cells are constantly stretching
What is receptor-mediated endocytosis?
use of receptors to get inside the cell (mode of entry with viruses)
What specific type of protein mediates the receptor-mediated endocytosis and how?
clathrin-coated proteins that assemble under the receptor-endocytic area of the membrane to take substance in
What are the 4 roles the cytoskeleton?
cell movement, chromosome separation, transport of organelles/things inside cell, provides shape and mechanical strength
What are microtubules and what does it establish in the cell?
cytoskeleton element made up of tubulin; establishes polarity in the cell (gives direction of transport)
Where is actin usually located within the cell and what is it’s role?
usually around the plasma membrane and is involved with the movement of the plasma membrane and other vesicles
What is the role of intermediate filaments?
provide cell structure and help cells adhere to neighboring cells
What are the 4 hurdles that viruses face after attachment?
receptors and polymerases, actin remodeling, ribosomes and viral mRNA compatibility, and viral-host cell mRNA competition
How are receptors and polymerases a hurdle for the virus to enter the host cell?
receptors = virus needs to have a receptor to be readily available and exposed to bind with to get into cell ||| polymerase = (depending on nature of nucleic acid) DdDp needs to be active/available for DNA viruses or same with RdRp for RNA viruses
How is actin a hurdle for the virus and what will it do to overcome this in order to enter the host cell?
actin (present on cell membrane) serves as a blockage for viral entry so virus needs to remodel actin via receptor-mediated endocytosis or cause it to remodel to bring virus in
How are ribosomes and viral mRNA compatibility hurdles for the virus?
viral mRNA do not have 5’cap = need to get it or find a way for ribosomes to recognize viral mRNA
How does the competition against host cell mRNA affect the virus?
virus only want their genome and transcripts to be translated and replicated = need to use up all of host-cell’s resources and can’t share with host cell mRNA
