Chapter 7.5 Flashcards
TRANSCRIPTION
copies the information encoded in a DNA base sequence into complimentary language of mRNA
TRANSLATION
Builds the protein. The actual construction of proteins.
Using the instructions from mRNA to build a protein by joining amino acid into a polypeptide sequence
It is the translation of the mRNA sequence into a sequence of amino acids
GENETIC CODE
is the set of rules by which a cell uses the nucleotides in mRNA to assemble amino acids into a protein. It also contains direction for starting and stopping translation
A CODON
is a group of 3 mRNA bases that corresponds to one amino acid or to a “stop” signal. Nearly all species use the same mRNA codons to specify the same protein
How many amino acids in life
20
What is typically the first codon of mRNA
AUG- the start codon ( methionine)
the 3 stop codons in mRNA
UGA, UAA, UAG
What participants are needed in translation
- mRNA
- tRNA
- Ribosomes
mRNA
product of transcription carries the genetic information that encodes a protein with each 3 base codon specifying a amino acid
tRNA
This bilingual molecule binds to a mRNA codon and to an amino acid.It contains an ANTICODON that is complimentary to one mRNA CODON
ANTICODON
is a 3 base loop that is complimentary to one mRNA codon
What is on the opposite end of of the anticodon on a tRNA
it forms a covalent bond to the amino acid corresponding to that codon
The anticodon for methionine
methionine codon on mRNA is AUG : on the transfer RNA the anti codon would be UAC with methionine attached to the opposite end.
RIBOSOME
. built of rRNA and proteins
. Anchors mRNA during translation
.They consist of a large and small subunit at join at the initiation of protein synthesis
Where are ribosomes in the cell
- free in the cytoplasm or
2. attached to the rough endoplasmic reticulum
The 3 steps of TRANSLATION
- Initiation
- Elongation
- Termination
INITIATION
- The leader sequence at the 5’ end of the mRNA molecules bonds with a small ribosomal unit.
- The first codon is usually AUG which attracts a tRNA that carries the amino acid methionine.
The methionine signals the start of the the polypeptide chain
3, A large subunit of ribosome attaches to the small subunit to complete initiation
ELONGATION
1.a tRNA molecule carrying the second amino acid , then binds ( a hydrogen bond) to the second codon on the mRNA
molecule.
- The first and second amino cid align forming a covalent bond= a peptide bond
- With the peptide bond in place the ribosome releases the first tRNA, which will pick up another methionine and be used again.
- The ribosome moves down my one codon. The steps are repeated.
ELONGATION FACTORS
are proteins that help the polypeptide to grow one amino acid at a time
TERMINATION
Elongation halts at a stop codon ( UGA< UAG, or UAA). No tRNA molecule corresponds to these codons.
- Instead proteins called RELEASE FACTORS bind to the stop codon prompting the release of the last tRNA from the ribosome.
- The ribosomal sub units separate from each other
- The polypeptide is released
The stop codons
UGA, UAG, UAA
. What happens in each stage of translation?
The steps of translation are initiation (ribosomal subunit binds to initiator codon), elongation of the polypeptide, and termination (release of the last tRNA from the ribosome, signified by a stop codon).
Where in the cell does translation occur
Translation occurs at ribosomes, which are either free in the cytoplasm or attached to the rough ER.
How are polypeptides modified after translation?
Polypeptides have to be folded into proteins; sometimes amino acids are cut out of the chain, and sometimes multiple polypeptides join together.
What bonds are formed with the anticodon and the codon on mRNA
HYDROGEN BOND
what bond are formed between the amino acids on the growing polypeptide chain
COVALENT PEPTIDE BONDS
What stabilizes proteins
CHAPERONE proteins
