BCH 313 Protein Synthesis Flashcards
What is DNA replication?
It is a biological process that occurs in living organisms and copies their DNA it is the basis for biological inheritance
Why is DNA replication considered semi conservative?
Because each replicated duplex daughter DNA molecule contains one parent strand and one newly synthesized strand
Each strand of the original DNA molecule acts as a template for the production of the complementary strand
What is the origin of a DNA molecule
Specific locations on the genome where DNA replication begins
What is the replication fork
A replication DNA fork is defined as a Y-shaped region where the parent DNA double helix splits into two strands
DNA polymerase function
Builds a new duplex DNA strand by adding nucleotides in the 5’ to 3’ direction also performs proofreading and error correction
Function of DNA Helicase
Unwinds DNA double helix at the replication fork
Function of DNA clamp
a protein which prevents DNA polymerase three from dissociation from the DNA parent strand
Function of single-strand binding proteins
bind to ssDNA and prevent the DNA double helix from re-annealing after DNA Helicase unwinds it, thus maintaining the strand separation
Function of topoisomerase
Relax in the DNA from a strand
Prevents supercoiling
Function of DNA gyrase
released strain of unwinding by DNA Helicase
Function of DNA ligase
Re-anneals the semiconservative strand and joins the Okazaki fragments of the lagging strand
Function of primase
provides a starting point of DNA for DNA polymerase to begin synthesis of the new DNA strand by producing a primer,
Primers may consistently be added to the lagging strand
Function of telomerase
lengthens telomerase DNA by adding repetitive nucleotide sequences to the ends of the eukaryotic chromosomes
What are okazaki fragments?
Okazaki fragments are short sequences of DNA nucleotides which are synthesized discontinuously and later linked together by the enzyme DNA ligase to create the lagging strand during DNA replication.
What is a genetic mutation
a mutation is an alteration in the nucleic acid sequence of the genome of an organism
Genetic mutation alter the regulation or
expression of gene and results in dysfunctional or nonfunctional protein synthesis.
What is a mutagen?
a chemical or physical agent capable of inducing changes in DNA called mutations
Describe the dna structureand the bond between nucleotides?
These are molecules composed of a deoxyribose sugar, with a phosphate and a base (or nucleobase) attached to it. These nucleotides are attached to each other in strands via phosphodiester bonds to form a ‘sugar-phosphate backbone’.
DNA polymerase can only add nucleotides in what direction
5’to 3’ direction
What is DNA transcription and its stages?
A process where genetic information of DNA is transcribed (copied) to mRNA, transcription is the synthesis of RNA from DNA resulting in the transfer of the information stored in double stranded DNA into single stranded RNA which is used to direct the synthesis of its proteins.
Transcription has 4 stages: initiation, elongation, termination and post-transcriptional processing
What is DNA translation and where does it occur?
- Translation is the process by which ribosomes convert the information carried by mRNA in the form of genetic code to the synthesis of new protein.
Translation occurs in cytosol on ribosomes and is guided by mRNA.
Eukaryotic protein synthesis involves more protein components with more intricate steps.
What are the requirements for translation?
- mRNA
- tRNAs
- Ribosomes
- Energy in the form of ATP and GTP
- Enzymes and specific protein factors, e.g. initiation factors, elongation factors, etc.
What are the stages of Eukaryotic Translation
- Activation of amino acids
- Initiation
- Elongation
- Termination and Release
- Folding and post-translational processing
Describe translation Stage 1: Activation of Amino Acids
For the synthesis of a polypeptide with a defined sequence, two fundamental chemical requirements must be met:
(1) the carboxyl group of each amino acid must be activated to facilitate the formation of a peptide bond, and
(2) a link must be established between each new amino acid and the information in the mRNA that encodes it.
These two requirements are met by attaching the amino acid to a tRNA in the first stage of protein synthesis.
Attaching the right amino acid to the right tRNA is critical and This reaction takes place in the cytosol, not on the ribosome.
Each of the 20 amino acids is covalently attached to a specific tRNA at the expense of ATP energy, using Mg2+-dependent activating enzymes known as aminoacyl-tRNA synthetases.
When attached to their amino acid, the tRNAs are said to be “charged.”
Describe translation Stage 2: Initiation
The mRNA bearing the code for the polypeptide to be made binds to the smaller of two ribosomal subunits and the initiating aminoacyl-tRNA. Carrying the initiator tRNA.
The large ribosomal subunit then binds to form an initiation complex. The initiating aminoacyl-tRNA base pairs with the mRNA codon AUG which signals the beginning of the polypeptide.
This process, which requires GTP, is promoted by cytosolic proteins called initiation factors (which are released after the binding of the large ribosomal sub-unit).
