Protein Synthesis Flashcards
What is the molecular definition of genes?
Sequences of nucleotides inside DNA that perform specific functions
What does the Garrod Hypothesis state?
One gene directs the production of one protein or enzyme
What does the Central Dogma Hypothesis state?
The genome is located inside the nucleus however proteins are synthesized outside the nucleus on the ribosomes
Why is one copy of DNA likely not sufficient?
Protein is required in large amounts. Thus one copy of DNA is likely, not sufficient because of the Garrod Hypothesis which states that one gene makes one protein
How is messenger RNA created in protein synthesis? how many copies of mRNA can be created?
DNA from the nucleus is copied into a single-stranded messenger RNA that is capable of encoding genetic information
-numerous copies of mRNA can be manufactured in the nucleus
What is transcription?
Copy of DNA information into mRNA
What is translation?
when Ribosomes read mRNA to make amino acid sequences into proteins
What are the three key characteristics of messenger RNA?
lit
- varies in length depending on the gene
- act as an intermediary between DNA and ribosomes
- translated into proteins by ribosomes
What are the two key characteristics of transfer RNA?
dc
- delivery of amino acids to ribosomes as they make proteins
- short and clover-shaped
What are the two key characteristics of ribosomal RNA?
ab
- help with the assembly and synthesis of ribosomes
- bind with proteins to form ribosomes
What codes for one amino acid? What is the start codon?
-three nucleotides are used to codes for one amino acid
-one codon codes for the start codon (AUG) while several others serve as stop codons
How many possible combinations of codons are there? What is the significance of this?
64 (because DNA consists of four different bases, and because there are three bases in a codon, and because 4 * 4 * 4 = 64) thus more than one codon can code for each amino acid
What is the codon chart used for?
Gives detailed information on which codon codes for which amino acid and the start and stop codons
What is the function of RNA polymerase?
Bonds to DNA segment meant to be transcribed. More specifically, it binds to the upstream region of the gene at the promoter and opens the helix
What is the function of the promoter?
Serve as the initial starting point for rna polymerase
Give a brief description of the structure of the promoter?
Consists of a region high of adenine and thymine (TATA Box) . Adenine and Thymine are held together by two hydrogen meaning they’re easier to separate than Cytosine and Guanine
Which direction does rna polymerase begin elongating?
In the 5’ to 3’ direction
When does rna polymerase begin elongating?
As soon as rna polymerase binds to the promoter
Does rna polymerase require a primer?
No
Is the promoter transcribed?
No
How many strands are transcribed?
Only one strand is transcribed
What is the template strand?
The strand chosen for transcription
What is the coding strand?
The strand that is not used for transcription (it will be identical to the newly formed rna except it has thymine instead of uracil)
What happens to rna polymerase once it reaches the terminator sequence? What is the significance of this?
the newly synthesized mRNA dissociates from the template
Rna polymerase is now free to transcribe another gene
What is the 5’ cap made of and why is it added to the gene?
made of 7 methyl guanosine
added to protect mRNA from digestion from other nucleases and phosphates in the cytoplasm
plays a role in initiating translation to create mature and stable messenger rna
Why is the 3’ Cap called the poly-A-Tail and why is it added to the gene?
-consist of approximately 200 adenine ribonucleotides by enzyme poly-A-polymerase
-further protects against degradation
What are spliceosomes?
Proteins that cut out non coding regions called introns and join together coding regions called exons
How are quantity and speed favoured over quality in the transcription phase of protein synthesis?
-there is no quality control to ensure mRNA transcript is correct. Hence many more errors are made
-a single gene may be transcribed 100 times because there are not enough correcting proteins to make sure enough proteins are being formed
What happens after transcription is complete?
The mRNA exits the nucleus and enters the cytoplasm to be translated by ribosomes
What does ribosome structure look like?
Ribosomes is composed of two subunits; a large and small set
Which direction do ribosomes add amino acids? How does it do this?
5’ to 3’ direction, adding a new amino acid for every codon it reads
What is the reading frame?
The section of mRNA that is read for polypeptide formation
What is the function of specific sites on the ribosome?
help guide the process of translation and the entry and exit of transfer RNA molecules with their amino acids
What is the structure of tRNA
-a single stranded nucleic acid whose structure resembles a clover leaf
-at one arm exist the anticodon which recognizes the mRNA codon
-the opposite arm carries the corresponding amino acid
What is the wobble hypothesis?
Every tRNA carries only one specific amino acid. Therefore, at least 20 distinct tRNA molecules must exist
-suggest that tRNA can recognize more than one codon by unusual pairing between the codon and the anticodon. It corrects for possible gene errors in mRNA
What are Aminoactyl- tRNA? How many of these enzymes are there?
-Enzymes responsible for adding appropriate amino acids to its corresponding tRNA
-there are 20 of these amino acids. One specific to each amino acid and tRNA
where is the P site located in the ribosome and what is its function?
the second binding site in transfer RNA in the ribosome
it holds the transfer RNA linked to the growing polypeptide chain
where is the E site located in the ribosome and what is its function?
it is the third and final binding site for transfer RNA
a site where tRNA molecules bind before they dissociate from the ribosome
where is the A site located in the ribosome and what is its function?
it is the first binding site in transfer RNA in the ribosomes
the a site binds incoming transfer RNA with the complementary codon on the mRNA
what is the release factor?
a protein that allows the termination of translation by recognizing that stop codon in the mRNA sequence
what is a transfer RNA
a molecule that makes sure the right amino acid is delievered to the mRNA
what is a polypeptide?
a chain of amino acids linked together by peptide bond.
What are ribosomes?
macromolecule machines that perform protein synthesis
what is an anti-codon?
a sequence of nucleotides that form three complementary base pairs to one or more codons
what are amino acids?
molecules that bind to form proteins
what is a peptide bond?
a bond that holds two amino acids in a polypeptide chain
