PP 11-13, Topic 4 - Control of Gene Expression Flashcards
What was the Nobel Prize in 2020 for Physiology or Medicine given for?
The three men discovered hepatitis C. and created a blood test to scan for hepatitis C. that reduced the number of people infected
What is COVID-19 caused by? What were the previous SARS epidemics?
Covid-19 (for 2019) is the disease caused by SARS-CoV-2 (“severe acute respiratory syndrome coronavirus 2”). It follows SARS-CoV (2003) and (MERS-CoV (causing Middle East Respiratory Syndrome)
How big is the SARS-CoV-2 genome and how many proteins does it code for?
SARS-CoV-2 genome is a 30,000 nucleotide single strand RNA, coding for ~29 proteins
What happens when the SARS-CoV-2 virus enters cells?
capable of being immediately translated as a “plus strand” RNA molecule
What proteins are unique to SARS-Cov-2? What receptor do they bind to in cells?
Spike proteins located on the surface bind to the ACE2 receptor in our bodies cells
How does the virus replicate in the cell?
The viral genome RNA is also transcribed into a complementary RNA (a “minus strand” RNA). This RNA is then itself transcribed over and over again to make more copies of the virus genome
What are the characteristics of viruses?
Viruses can’t reproduce outside a host cell and depend on host cell machinery to replicate and reproduce
What are important virus proteins?
four structural proteins make the virus coat
“replicase” proteins make copies of the virus genome (virus makes an RNA-dependent RNA polymerase complex)
How does the virus replicate?
The genomic RNA (gRNA) has a 5′-cap and a 3′-poly(A) tail and can act as an mRNA for immediate translation of the viral polyproteins by host ribosomes
Once virus proteins are produced replication of the genome can occur
Multiple copies of the genome are produced, packaged into the virus coat proteins, and the virus exits the cell to infect new cells
What are chromatin altering factors in eukaryotes and what do they do?
What is epigenetics?
stable (heritable) differences in phenotype unaccompanied by changes in genotype
What role does the environment have on epigenetics?
What diet a impactful diet consist of?
Supplements included high levels of folic acid, vitamin B12, choline, and betaine
Mice are identical (identical DNA sequences) yet develop to be very different from one another
How is methylation recognized?
What does methylation do to the cytosine on the complementary strand?
On the fifth carbon a H3C group is added
Areas of cytosine on the opposite strand are recognized by maintenance methyltransferases
Why is gene expression important?
What is gene expression?
All cells have identical DNA sequence, but specialize through gene expression.
Gene expression is a complex process cells used to direct the synthesis of thousands of proteins and RNAs encoded in their genome
What can specialized cells do?
alter their gene expression based on extracellular cues
What is the promoter of prokaryotes and eukaryotes?
include the transcription initiation site (where RNA synthesis begins), nearby sequences that recognizes sites for proteins that associate with RNA polymerase (sigma factor in bactera, GTFs in eukaryotes)
What are regulatory DNA sequences?
Do they work by themselves?
What must they work with?
What starts transcription?
Regulatory sequences cannot work alone
Regulatory sequences must be recognized by transcription regulators
the binding of the transcription regulator to the regulatory sequences initiates transcription
What is the benefit of dimer binding of transcription regulators?
Dimerization doubles the contact area with DNA, increasing strength and specificity of DNA interaction
What happens when trytophan concentrations are low?
When tryptophan is low - The operon is transcribed and the mRNA is translated to synthesize amino acid
When tryptophan is high - the amino acid trytophan is fed back into in active Trp receptor, activating it, and blocking the binding of the RNA polymerase
What are nucleosomes?
molecule of DNA wrapped around a core of 8 histone proteins that form an octamer
What are the things involved in eukaryotic gene expression?
activator protein binds to enhancer
DNA wraps around ( in a sidways U) and the mediator binds to the bottom of the activator protein
the mediator binds to TFs which help facilitate the binding of RNA polymerase
