Exam 2 Flashcards
What is a codon?
3 Nucleotides
Central Dogma?
DNA(Transcription in Nucleus)->RNA(Translation in Cytoplasm)->Protein
What does tRNA do?
- Carry Amino Acids
- Work with ribosomes to produce polypeptides
What is an Anticodon?
3 nucleotide sequence that is complementary to mRNA codon.
What is Translation?
- mRNA to Protein
What are the Translation Components?
- Ribosome
- Initiation factors
- Elongation Factors
- Anticodon
- Initiator tRNA
What is Charging?
- Chemically linking amino acids to tRNAs
What is Aminoacyl tRNA synthetases?
- Recognize specific tRNAs
- One for each Amino acid
Primary Functions of the Ribosome?
- Decode the mRNA
- Form peptide bonds
What is Peptidyl Transferase?
- Enzomatyic component a ribosome.
- Forms peptide bonds between amino acids.
What is the P-Site?
- Binds the tRNA attached to the growing peptide chain
What is the A-site?
- Binds the tRNA carrying the next amino acid
What is the E-site?
- Binds the tRNA that carried the last amino acid.
In prokaryotes, initiation complex includes?
- Initiator tRNA charged with N-formylmethionine
- Small ribosomal subunit
- mRNA strand
What are the 3 steps of Prokaryotic translation?
- Initiation
- Initiator tRNA – formylmethionine
- Initiation factors
- Elongation
- Addition of tRNA/A.A.
- Termination
What happens during Prokaryotic Elongation in Translation?
- Elongation adds amino acids
- 2nd charged tRNA can bind to empty A site
- Requires elongation factors
- A peptide bond can then form
- Addition of successive amino acids occurs as a cycle
When does Elongation Stop In Prokaryotic Translation?
- Elongation continues until the ribosome encounters a stop codon.
- The stop codons are recognized by release factors.
What are the differences between prokaryotic and eukaryotic translation?
- Eukaryotic mRNA is more stable
- Transcription and translation are separate processes.
Charging a tRNA depends on which enzyme?
- Aminoacyl tRNA synthetases
During translation, what molecule bears the anticodon? The codon?
- tRNA
- mRNA
What is a base substitution?
- Substitute one base for another
What is Silent mutation?
- Same amino acid inserted
What is a Missense Mutation?
- Changes amino acid inserted
What is a Nonsense Mutation?
- Changes to a stop Codon
What is a frameshift Mutation?
- Addition or deletion of a single base
- Alter reading frame downstream
how is gene expression controlled?
-Gene expression is often controlled by regulatory proteins binding to specific DNA sequences.
What are the DNA motifs?
- Helix-turn-helix motif
- Homeodomain motif
- Zinc finger motif
- Leucine zipper motif
What is Induction?
- Enzymes for a certain pathway are produced in response to a substrate
What is Repression?
- Capable of making an enzyme but does not
What is Prokaryotic Regulation?
- Prokaryotic cells often respond to their environment by changes in gene expression
What is an operon?
- A genetic unit consisting of structural genes and regulatory elements
Constitutively Definition?
- Constantly Expressed
What is Inducer exclusion?
- Presence of glucose inhibits the transport of lactose into the cell
Preferential use of glucose in the presence of other sugars?
- Mechanism involves activator protein that stimulates transcription
- Catabolite activator protein (CAP) is an allosteric protein with cAMP as effector
- Level of cAMP in cells is reduced in the presence of glucose so that no stimulation of transcription from –CAP-responsive operons takes place
When lactose is high?
- Glucose is scarce
- cAMP is high
- Abundant lac mRNA synthesized
When lactose is low?
- Glucose is high
- cAMP is low
- Little lac mRNA synthesized
A mutation in the P region of the lac operon would most likely result in?
- Reduced expression of lac
The lac operon is normally expressed when?
- in the presence of lactose and the absence of glucose.
Major differences between eukaryotic and prokaryotic regulation?
-Eukaryotes have DNA organized into chromatin which complicates protein-DNA interaction
What is Basal Expression?
- Low Expression
What are General transcription factors in eukaryotic transcription?
-Necessary for the assembly of a transcription apparatus and recruitment of RNA polymerase II to a promoter, basal level of transcription
What are the Specific transcription factors in eukaryotes?
- Increase the level of transcription in certain cell types or in response to signals
- Cell type specific
- Condition specific
Why are Restriction enzymes significant?
- Allow a form of physical mapping that was previously impossible
- Allow the creation of recombinant DNA molecules (from two different sources)
Restriction Enzymes?
- Recognize specific DNA sequences
- Cleave at a specific site within the sequence
- Can lead to “sticky ends” that can be joined
- Palindromic sequences
- Same sequence in both directions
What is DNA ligase?
- Joins the two fragments forming a stable DNA molecule
- Catalyzes formation of a phosphodiester bond between adjacent phosphate and hydroxyl groups of DNA nucleotides
- The same enzyme joins Okazaki fragments on lagging strand in replication
What is Gel Electrophoresis?
-Separate DNA fragments based on size
-The gel made of agarose or polyacrylamide
-Subjected to an electrical field
-Negatively-charged DNA migrates towards the positive pole
-Larger fragments move slower, smaller move faster
-DNA is visualized using fluorescent dyes
Ethidium bromide
What is the sense strand?
- It’s the original strand that goes from 5’-> 3’
What is molecular cloning?
- Isolation and expansion of a specific DNA sequence
What is a DNA Library?
- A collection of DNAs in a vector that taken together represent the complex mixture of DNA
