Biology 189 Ch.7 review
mRNA vaccine example
Covid vaccine consists of COVID-19 spike (coat) protein mRNA and lipids (similar to cell membrane lipids)
Where does translation occur?
Cytoplasm
DNA can be tightly bound to histone proteins that can prevent gene expression. Chemical modifications of histones can open up (or close off) DNA for transcription
DNA availability
What are the 6 mechanisms for regulating gene expression in eukaryotes?
DNA availability, Transcription factor availability, mRNA processing (alternative splicing), mRNA transport from nucleus, RNA degradation, and Protein processing and degradation
Polymers made up of nucleotide monomers
Nucleic acids:
Where does Transcription take place in the nucleus and what is it performed by?
Nucleus, performed by RNA Polymerase.
Protein-based infectious particles
Prions
In humans, how many genes spread across how many chromosomes?
25,000 genes spread across 23 chromosomes
Chromosome pairs are called what? what do they contain?
homologous chromosomes, they contain the same genes in the same locations
What happens in the attachment step in viral replication?
virus binds to host cell surface receptors
What happens in the penetration step in viral replication?
virus genome enters the host cell - Phagocytosis - Injection
How many circular chromosomes do prokaryotes typically have?
a single circular chromosome
Define start Condon
a specific codon that starts amino acid incorporation
Define genome
all of the DNA inside of a cell
The strands of DNA run
anti-parallel
In Elongation, RNA polymerase then begins to move along what and reads what?
begins to move along the DNA strand and "reads" the DNA template
Bacteria can turn genes on or off depending on what?
depending on what resources are available
Sugar and phosphate groups make the rails aka the...
"sugar-phosphate backbone"
-Misfolded proteins that cause other proteins to misfold - Result in massive accumulation of misfolded proteins resulting in cell death - Mad cow disease is caused by prions- typically from eating nervous tissue of previous infected cows
"zombie proteins"
What happens in the elongation step of translation?
- After Met, the ribosome moves the mRNA down one codon - The next codon is read and the appropriate tRNA enters the ribosome - Ribosome makes covalent peptide bond between amino acids then kicks tRNA out as ribosome moves down one codon -Next codon is read, new tRNA enters, and next amino acid is added
What happens in the termination step of translation?
- Specific "stop codons" indicate where the protein ends - Protein release factors bind to the stop codons and cause ribosomes to release from mRNA
What happens when the ribosome "reads" the mRNA codon?
- The appropriate tRNA enters the ribosome - Codon-anticodon base pairing (RNA-RNA base pairing: C-G; A-U) -The new amino acid is covalently bound to the previously-added amino acid in the growing polypeptide chain
1 parent cell =
2 daughter cells
What are the three steps in translation?
1. Initiation 2. Elongation 3. Termination
Transcription takes place in the nucleus in 3 steps, what are those steps?
1. Initiation 2.Elongation 3.Termination
All eukaryotic polypeptide sequences have Met as what?
1st a.a
How much energy is spent on gene expression?
90%
A segment of DNA that contains instructions to make a specific protein or RNA molecule
A gene
What is the start Condon for eukaryotic?
AUG and codes for the amino acid Methionine (Met)
What are the 4 different nucleotides (different nitrogenous bases)?
Adenine (A) and Guanine (G), Cytosine (C) and Thymine (T): Pyrimidines
What does not work against viruses?
Antibiotics
What are the 5 stages of viral replication?
Attachment, penetrations, synthesis, assembly, and release
The sequence of one strand can be used to determine the sequence of the other strand
Complementary base pairing
which step in transcription adds complementary RNA nucleotides to a growing RNA molecule as it moves down the gene
Elongation
Segments joined together to make mature mRNA
Exons
The 20+ different amino acids provide proteins with a huge variety of molecular interactions such as?
H-bonds, hydrophilic, hydrophobic, charged, uncharged, etc.
Segments removed from pre-mRNA- trash RNA
Introns-
A group of genes that function to break down lactose sugar but are expressed only in the presence of lactose sugar
Lac operon
What happens when lactose is present in regulating gene expressions in prokaryotes?
Lactose physically binds to the repressor and the repressor falls off of the operator
Viral genome incorporated into host genome (prophage) - Viral genome maintained within host until conditions trigger entry into lytic phase - Stressful conditions can cause this transition - Sometimes host genes can be incorporated into viral genome
Lysogenic phase
What are the two potential lifecycle phases?
Lytic and Lysogenic phases
Rapid viral replication which causes infected cells to die - Massive release of new viral particles into the organism/ environment
Lytic phase
Any external agent that induces mutations
Mutagens
Describe a tRNA molecule
One end binds to a specific amino acid, the other end has 3 nucleotides that are complementary to the codon= anticodon
A DNA sequence between the promoter and the protein-coding genes and serves as a regulatory region
Operator
A clustered group of genes related to a specific function that can be turned on or off as needed
Operon
Code the required proteins
Operon genes
Site where RNA polymerase binds
Promoter
Acts as a signal for where the gene starts and what strand to use as template
Promoter region
Just like mRNA, proteins can be regulated at the level of production and degradation. Some proteins get degraded as they are transcribed while others can be maintained long after production.
Protein processing and degradation
Adenine (A) and Guanine (G):
Purines
Cytosine (C) and Thymine (T):
Pyrimidines
Enzymes in cell actively degrade RNA. mRNA can be chemically modified which can change its "lifespan" and the likelihood that a transcript will be made into a protein or not.
RNA degradation
Proteins known as transcription factors recruited to promoter and guide RNA polymerase to bind with what?
RNA polymerase binds with template DNA strand at the correct location
What happens when no lactose is present in regulating gene expressions in prokaryotes?
Repressor proteins bind to the operator and physically stops RNA polymerase and operon gene expression
What is translation performed by?
Ribosomes
In translation, what do the ribosomes read?
Ribosomes read 3 bases at a time (Condon)
Point mutations that do not change the protein's amino acid sequence • Genetic code redundancy tolerates mutations in the third base (wobble) position of a codon
Silent mutations
Mutations can affect what?
Single DNA base, a few bases, or large portions of chromosomes
The process of removing introns and connecting exons from pre-RNA to form mature mRNA
Splicing
which step in transcription recognizes the termination sequence and releases from the DNA • mRNA molecule released
Termination
What happens in the step of initiation in translation?
The mRNA cap helps mRNAs associate with ribosomes but does not specify any amino acids
Specialized RNA molecules called "transfer RNA" (tRNA) carry specific amino acids to what?
The ribosome
What happens in the assembly step in viral replication?
The viral particles assemble and the genetic information moves inside
A gene's DNA sequence is rewritten into a messenger RNA (mRNA) molecule in the nucleus
Transcription
Proteins that bind to promoter regions of DNA and help direct RNA polymerase to gene• No transcription factor - no gene expression
Transcription factor availability
Converting the mRNA code into a polypeptide (protein) sequence
Translation
The mRNA molecule leaves the nucleus and enters a ribosome (free or bound) where the mRNA codes for the specific amino acids in a polypeptide chain
Translation
Very small protein shells that contain genetic material made of either DNA or RNA
Viruses
What describes the flow of information from DNA to RNA to protein molecules
central dogma
What do Polysomes increase?
increase protein synthesis efficiency
Removal of certain introns/ exons can have dramatic effects on downstream protein products (see earlier slide)
mRNA processing (alternative splicing)
Segments of RNA are removed and the remaining segments are joined together
mRNA splicing
If mRNA is not specifically transported from the nucleus, it will not become a protein
mRNA transport from nucleus
What does alternative splicing + post-translational modifications increase?
massively increase total number of proteins a cell can make vs. # genes
How many linear chromosomes do prokaryotes typically have?
multiple linear chromosomes
In sexually reproducing organisms- chromosomes come in pairs, from where do they come from?
one chromosome from the mother and one chromosome from the father
Paired nitrogenous bases joined with hydrogen bonds
rungs
Short RNA molecules that fold into a unique "t" shape
tRNA
What happens in the synthesis step in viral replication?
the host cell is hijacked to produce millions of copies of the viral genome and viral proteins - Host cell provides all of the resources- ATP, ribosomes, nucleotides, amino acids, enzymes
What happens in the release step in viral replication?
the host cell releases the newly formed viral particles - Some viruses kill host cell during release (lysis) while others are released via exocytosis (vesicles)