Ch. 5.3- Protein Synthesis Flashcards
Define protein synthesis. What is another name for it?
Genetic information in the cell is read and used to make gene products. Also called gene expression.
Define transcription
When genes are copied into a new format. RNA
Translation
Reading of mRNA to make proteins.
What is the first step (initiation) of transcription?
1) RNA polymerase binds to the promoter (beginning region of the gene in DNA) The RNA polymerase then unwinds the DNA to reveal a single stranded template of the gene that will be transcribed into RNA.
What is the second step (elongation) of transcription?
During elongation, the enzyme advances along the single strand of DNA laying down complimentary ribonucleotides.
What is the third step (termination) of transcription?
Happens when the RNA polymerase reaches the end of the gene. Termination sequence signals the polymerase to fall of the DNA and the new RNA transcript is released.
Where does transcription occur in eukaryotes and prokaryotes?
Eukaryotes- happens in nucleus
Prokaryotes- happens in the cytoplasm
Define reverse transcription
When some cells and viruses use RNA as a template to build copy DNA.
What is the term for cells and viruses that carry out reverse transcription?
Reverse transcriptases
What are the three types of RNA used in proteins synthesis?
mRNA
tRNA
rRNA
What does mRNA do?
Carries genetic messages in genetic triplet code (codons) and is translated to build a protein.
What does tRNA do?
Cloverleaf shaped molecule that serves as a an adaptor that ushers amino acids into the ribosome during proteins synthesis.
What does rRNA do?
Takes on complex stem and loop structures and combines with proteins to build ribosomes.
Where are codons found?
only in mRNA.
What is the role of codons?
They specify the amino acid type to be built or signal the stop of translation.
What are the descriptive terms for mRNA that carry code for multiple types of amino acids as apposed to carrying code for only one.
Polycystronic
Monocystronic
What is the role of tRNA?
They bring the correct amino acid to the ribosome. These carry an anticodon loop that is complimentary to the codon part of mRNA which ensures that the right amino acids arrive in the right order.
What is the role of rRNA?
They all help ribosomes “read” or scan an mRNA molecule and form peptide bonds between amino acids to build a protein- making complex three dimensional structures.
Define exon
The segments of mRNA sequences that are decoded to build proteins.
Define introns
The segments of mRNA code that are not decoded to build proteins. These determine how much protein is made and what protein is present in a cell.
Define splicing
When intones are cut out of the mRNA in the nucleus so that the correct sequence of RNA code can be read by the ribosomes outside the nucleus.
What is the name of the thing that does the splicing in the removal of introns?
Spliceosome
Define sense condons
Codons that encode amino acids
Define non-sense condons
codons that encode stop signals
What is the core structure of amino acids made out of?
A Amine and a Carboxyl groups
What are the three sites of a ribosome?
Exit site (E), peptidyl site (P), and acceptor site (A).
Define polysomes
Collections of many ribosomes on a single mRNA strand.
What are the three phases of translation?
Initiation
Elongation
Termination
What happens in translation during initiation?
Ribosome attaches to mRNA till it find a “start code” where it adds the first amino acid
What happens in translation during elongation?
Ribosomes attach to mRNA and elongate the protein. Then tRNA bring amino acids in an anticodon formation that (if matched to the condon formation of mRNA correctly) are bonded by the ribosome with a peptide bond. tRNA enters via the A site and leaves via the E site of ribosomes.
Define peptide bonds
Type of covalent bond where the amine group of an Amino acid covalently bonds with the carboxyl group of another Amino acid. This forms polypeptides of proteins. This chemistry happens in the P and A sites of the ribosomes.
Where does the initiator tRNA enter the ribosome?
The P site.
What happens during translation in the termination phase?
The ribosome encounters a “stop” or “nonsense” codon, and translation is terminated.
What is another term for a “stop codon”
A nonsense codon
