Translation-14 Flashcards
What is translation?
process by which ribosomes read the genetic message in the mRNA and produce a protein product according to the message’s instruction
What components does Translation require?
mRNA tRNA Ribosomes Translation factors -most cells use a substantial amount of energy on translation
What are the different types of RNA included in translation?
Messenger RNA (mRNA): carries the genetic instructions for protein synthesis from DNA in the nucleus to the ribosomes in cytoplasm
Ribosomal RNA (rRNA): major component of the ribosomes; protein synthesis
Transfer RNA (tRNA): brings amino acids to ribosomes for protein synthesis
What is mRNA?
messenger RNA which carries the genetic information from nucleus to cytoplasm for protein synthesis
Each group of 3 nucleotides in the mRNA is a “codon”, which codes for 1 amino acids
Where are ribosomes and rRNA made?
Where are rRNA found?
They are synthesized in the nucleolus and shipped out of nucleolus through the nuclear pores to cytoplasm in eukaryotic cells
rRNA are found in the ribosomes and account for 80% of the total RNA present in the cell
Sub units in the Ribosome:
There are 2 pieces or subunits to every ribosome-large subunit and small subunit
Each subunit is made up of one or more rRNA and a variety of ribosomal proteins and act as the site of proteins synthesis
Ribosome and their binding sites:
Each ribosome has an mRNA binding site and 3 tRNA binding sites
What are the 3 binding sites? tRNA
facilitate coupling of tRNA anticodon to mRNA codon
- A site (aminoacyl-tRNA site)
- holds tRNA carrying next amino acid to be added to a polypeptide chain - P site (peptidyl-tRNA site)
- holds tRNA carrying growing polypeptide chain - E site (exit site)
- empty tRNA leaves ribosome from exit site
What are the characteristics of tRNA? How many bases make up the anticodon?
Transfer RNA (tRNA) are short RNAs that fold into a characteristic cloverleaf pattern
Each tRNA has 3 bases that make up the anticodon
-these base pair with the 3 bases of the codon on mRNA during translation
What is the function of tRNA?
tRNA brings amino acids to the ribosome for protein production
What does Aminoacyl-tRNA synthetase catalyze?
Catalyzes the attachment of amino acids to tRNA
-one for each different amino acids
Reactions result in tRNA with amino acid attached or charged tRNA or aminoacyl tRNA
How do we code for amino acids with only 4 bases?
Nucleotide bases exist in triplets for a codon
3 bases=1 codon=1 amino acid
Genetic code, what is the start codon (first base 5’ end)?
AUG
methionine
(met)
Genetic code, what is the stop codon (third base 3’ end)?
UAA
UAG
UGA
What are the 3 stages of translation?
Initiation
-mRNA, first tRNA and ribosomal subunits assemble
Elongation
-Synthesis from start codon to stop codon
Termination
-Complex disassembles at stop codon releasing completed polypeptide
What occurs during Initiation, what starts binding here?
1- Ribosome binding site on mRNA binds to complementary sequence on small subunit of ribosome, with the help of proteins called initiation factors
2- Initiator tRNA brings in the first amino acid “methionine (Met)” and binds to mRNA’s start codon,
AUG”
3-Large subunit of ribosome binds -> placing initiator tRNA in the (P-site -holds tRNA carrying growing polypeptide chain)
Elongation starts (step 4)
What occurs during Elongation, what starts binding here?
4- Incoming tRNA binds to the codon in the A site-(holds tRNA carrying next amino acid to be added to a polypeptide chain) via complementary base pairing between anticodon and codon
5- Amino Acid in the P site:
- breaks the bond with its tRNA
- forms a peptide with the amino acid in the A site
6- Translocation
- Ribosome moves down to the next codon on mRNA
- tRNAs shift over one spot
- Repeat the Cycle
- Incoming tRNA enters the A site
- peptide bond formation (with adjacent amino acid)
- translocation
What occurs during the termination stage of Translation?
- Occurs when a stop codon is revealed in A site-> A protein called a release factor enters the A site
- Release factor promotes the hydrolysis of the bond linking the tRNA in the P-site with its polypeptide-. releases polypeptide and tRNAs
- Ribosomal subunits, mRNA and protein release factor all separate from one another
How are amino acids joined together to make a polypeptide?
Amino acids join together through a condensation reaction forming peptide bonds where water is removed and is made a product
Each mRNA molecule is simultaneously translated by many……
ribosomes, all reading the mRNA from 5’ to 3’ and synthesizing the polypeptide
Relationship between nucleic acids and proteins, What determines the sequence of amino acids in a protein?
Sequence of bases in DNA determines sequence of amino acids in a protein
Relationship between nucleic acids and proteins, What does the sequence of amino acid determine?
Sequence of amino acids determines a protein’s structure and function
Small changes in the DNA doesn’t cause that much of a difference in the protein (true/false)
False, Small changes in the DNA may cause large changes in a protein
What makes proteins in the cell?
Free floating ribosomes
