Amanita phalloides
a poisonous mushroom called the death cap. consumption of this mushroom leads to gastrointestinal symptoms such as ab pain, cramping, vomiting, diarrhea then liver cells die causing permanent liver damage
alpha amanitin
the mushrooms contain this protein which consists of a short peptide of 8 amino acids that form a circular loop. alpha amanitin is a potent inhibitor of RNA polymerase II
what does the death cap inhibit
RNA polymerase II which is responsible for transcribing protein-encoding genes in eukaryotes. the alpha amanitin prevents the RNA polymerase from moving across the DNA template. RNA synthesis slows from a normal speed to only a few nucleotides per minute
what is the job of RNA Polymerase II
to bind to genes and synthesize RNA molecule complementary to DNA template strands by adding one nucleotide at a time to the growing RNA chain.
what are the long term effects of ingesting alpha amanitin
the RNA polymerase II won't transcribe enough, protein synthesis will slow and the required function stops causing cell death. The toxin accumulates in the liver killing off liver cells. A transplant is nearly crucial for survival
what is the first step in the central dogma pathway
to transfer from DNA the genotype to protein which is the phenotype. The central dogma is essentially the transfer of information from DNA to RNA to Protein
what does transcription need in order to occur
required RNA nucleotides, a DNA template and a number or protein components
Life's 2 basic function
organisms must be able to store and faithfully transmit genetic information through reproduction. Secondly the must have the ability to catalyze reactions
ribozymes
catalytic RNA molecules that have the ability to cut out parts of their own sequence connect certain RNA molecules, replicate others, and even catalyze the formation of peptide bonds between amino acids
structure of RNA
a polymer consists of nucleotides joined together via phosphodiester bonds.
differences between RNA structure and DNA structure
RNA consists of Ribose whereas, DNA consists of deoxyribose. RNA molecules have a free 2 prime carbon atom on the ribose sugar. RNA is more unstable than DNA because DNA lacks a free hydroxyl group. RNA has uracil instead of thymine
secondary structures of RNA
hairpin loops or stem loops
when two regions within one RNA molecule pair up the strands in the regions are antiparallel with pairing between cytosine and gaunine and between uracil and adenine
hair pin loops
how is secondary structure determined
by the base sequence of the nucleotide strand. RNA can assume different structures
Ribosomal RNA
rRNA and ribosomal protein subunits make up the ribosome the site of protein assembly
messenger RNA
mRNA carries the coding instructions for polypeptide chains from DNA to a ribosome. after attaching to the ribosome an mRNA molecule specifics the sequence of amino acids in a polypeptide chain and provides a template for joining amino acids
pre mRNAs
large precursor molecules: these are the immediate products of transcription in eukaryotes. pre mRNAs are modified extensively before become mRNA and exiting the nucleus for translation to become a protein
do bacterial cells posses pre mRNA
no, in bacterial cells since there is no nucleus transcription and translation occurs at the same time
similarities between DNA and RNA
both composed of nucleotides, have adenine, guanine and cytosine, nucleotides are joined by phosphodiester bonds
what is the function of ribosomal RNA
it is located in the cytoplasm and makes up the structural and functional components of the ribosome
what is the function of mRNA
located in the nucleus until it is mature and can be put into the cytoplasm. these carry the genetic code for proteins
tRNA
located in the cytoplasm which helps to incorporate amino acids into the polypeptide chain
small nuclear RNA (snRNA)
located in the nucleus of eukaryotes, which process pre-mRNA
small nucleolar RNA or snoRNA
located in the nucleus of eukaryotes and helps in the processing and assembly of pre-mRNA
microRNA or miRNA
located in the nucleus and cytoplasm of eukaryotes which inhibits the translation of mRNA
small interferring RNA siRNA
located in the nucleus and cytoplasm of eukaryotes which trigger the degradation of other RNA molecules
piwi interacting RNA
located in the nucleus and cytoplasm of eukaryotes which suppresses the transcription of transposable elements in reproductive cells
CRISPR RNA
occurs in prokaryotes and assists in the destruction of foreign DNA
small nuclear ribonucleoproteins
small nuclear RNAs which binds with small protein subunits
which RNAs carry out interference
small interfering RNAs and microRNAs
True or false all cellular RNAs are synthesized from DNA templates
true this occurs during transcription
Is transcription a highly selective process
Yes
Transcription requires 3 major components
1. A DNA template
2. Raw materials needed to build a new RNA molecule
3. The transcription apparatus consisting of the proteins necessary to catalyze RNA synthesis
Transcription unit
A stretch of DNA that encodes an RNA molecule and the sequences necessary for transcription
Promoter
A DNA sequence that the transcription apparatus recognizes binds to
What does the promoter do
It determines the transcription start site
RNA coding region
A sequence of DNA nucleotides that are transcribed into an RNA molecule
Terminator
A sequence of nucleotides that signals where transcription should end
When does transcription stop
When the terminator sequence has been copied into RNA
RNA polymerase
Carries out all of the essential steps for transcription with the help of accessory proteins that join and leave the polymerase
In bacterial RNA polymerase the core enzyme consists of
5 subunits two copies of alpha, a beta, a single copy of beta prime, and a single omega
How many polymerases do bacteria cells typically have
1 type of RNA polymerase which catalyzes all the classes of bacterial RNA
Bacterial RNA polymerases
...
Sigma factor
Controls the binding of RNA polymerase to the promoter
What happens if sigma is not present
Then the DNA polymerase would initiate transcription at a random point along the DNA
Holo enzyme
When sigma associate with the core enzyme the structure is called this type of enzyme
How many polymerases does a normal eukaryote have
3
Types of RNA polymerases found in eukaryotes
DNA polymerase 1 2 and 3
RNA polymerase 1
Transcribes ribosomal RNA
RNA polymerase 2
Transcribes pre mRNAs
RNA polymerase 3
Transcribes other small RNA molecules such as tRNA, small r RNA some miRNAS and snRNA
What type of polymerases are found in plants
Polymerase 4 and 5
RNA polymerase 4 and 5
Transcribe nucleotides that play a role in DNA methylation and chromatic structure
Three stages of transcription
1. Initiation
2. Elongation
3. Termination
Initiation
In which the tenacity ion apparatus assembles on the promoter and begins the synthesis of RNA
Elongation
DNA is threaded through RNA polymerase. the polymerase unwinds the DNA and adds new nucleotides, 1 at a time to the 3 prime end of the growing RNA strand
Termination
The recognition of the end of the transcription unit and the separation of the RNA molecule from the DNA
Initiation requires these steps to be done
Promoter recognition
Formation of the transcription bubble
Creation of the first bonds between RNTPS
Escape of transcription apparatus from the promoter
Consensus sequences
Short stretches of common nucleotides
What does it mean when a consensus sequences is present
That the sequence is associated with an important function
Most commonly encountered consensus sequence found in almost all bacterial promoters
-10 consensus sequence often written as Tatat
Common bacterial promoters consensus sequences
-10 and -35