RNA and protein synthesis Flashcards
What is RNA?
It is a single polynucleotide strand and it contains uracil as a base instead of thymine
What is mRNA?
It is made during transcription, it carries the genetic code from the DNA to the ribosomes, where it is used to make protein during translation. mRNA is a single polynucleotide strand. Groups of three adjacent bases are usually called codons
What is Transfer RNA (tRNA)
tRNA is involved in translation. It carries the amino acids that are used to make proteins to the ribosomes.
tRNA is a single polynucleotide strand that’s folded into a clover shape.
They have three bases at one end called anticodons.
What is transcription?
1) Transcription starts when RNA polymerase attaches to the DNA double-helix at the beginning of a gene
2) The hydrogen bonds between the two DNA strands in the gene are broken by a DNA helicase attached to the RNA polymerase. This separates the strands and exposes some of the bases.
3) One of the strands is then used as a template to make an mRNA copy.
4) RNA polymerase lines up free RNA nucleotides alongside the exposed bases on the template strands. The free bases are attracted to the exposed bases. Complementary base pairing means that the mRNA strand ends up being a complementary copy of the DNA template strand
5) Once the RNA nucleotides have paired up with their specific bases on the DNA strand, they are joined together by RNA polymerase , forming mRNA molecule.
6) The RNA polymerase moves along the DNA, separating the strands and assembling the mRNA strand.
7) The hydrogen bonds between the uncoiled strands of DNA re-form once the RNA polymerase has passed by and the strands coil back into a double helix
8) When RNA polymerase reaches a particular sequence of DNA called a stop signal, it stops making mRNA and detaches from the DNA.
9) mRNA moves out of the nucleus through a nuclear pore and attaches to a ribosome in the cytoplasm, where the next stage of protein synthesis takes place.
What is Translation?
This is when amino acids are joined together to make a polypeptide chain.
1) The mRNA attaches itself to a ribosome and transfer RNA molecules carry amino acids to it. ATP provides the energy needed for the bond between amino acid and the tRNA molecule to form
2) A tRNA molecule, with an anticodon that’s complementary to the first condon on the mRNA, attaches itself to the mRNA by specific base pairing.
3) A second tRNA molecule attaches itself to the next codon on the mRNA in the same way
4) The two amino acids attached to the tRNA molecules are joined by a peptide bond. The first tRNA molecule moves away, leaving its amino acid behind.
What is transcription? (Adam)
Transcription is the process of making messenger RNA from a DNA template.
What is translation? (Adam)
Translation involves “decoding” a messenger RNA (mRNA) and using its information to build a polypeptide, or chain of amino acids. For most purposes, a polypeptide is basically just a protein (with the technical difference being that some large proteins are made up of several polypeptide chains).
What are the stages in Translation? (Adam)(Khan Academy)
Initiation (“beginning”): in this stage, the ribosome gets together with the mRNA and the first tRNA so translation can begin.
Elongation (“middle”): in this stage, amino acids are brought to the ribosome by tRNAs and linked together to form a chain.
Termination (“end”): in the last stage, the finished polypeptide is released to go and do its job in the cell.
What are stop codons?
Stop codons mark the polypeptide as finished.
What is the codon AUG?
One codon, AUG, is a “start” signal to kick off translation (it also specifies the amino acid methionine
What is the initiation stage of Translation?
In order for translation to start, we need a few key ingredients.
These include:
A ribosome (which comes in two pieces, large and small)
An mRNA with instructions for the protein we’ll build
An “initiator” tRNA carrying the first amino acid in the protein, which is almost always methionine (Met)
During initiation, these pieces must come together in just the right way. Together, they form the initiation complex, the molecular setup needed to start making a new protein.
What is the elongation stage of Translation?
I like to remember what happens in this “middle” stage of translation by its handy name: elongation is when the polypeptide chain gets longer. Our first, methionine-carrying tRNA starts out in the middle slot of the ribosome, called the P site. Next to it, a fresh codon is exposed in another slot, called the A site. The A site will be the “landing site” for the next tRNA, one whose anticodon is a perfect (complementary) match for the exposed codon.
What is the termination stage of Translation?
Polypeptides must eventually come to an end. Translation ends in a process called termination. Termination happens when a stop codon in the mRNA (UAA, UAG, or UGA) enters the A site. Stop codons are recognized by proteins called release factors, which fit neatly into the P site (though they aren’t tRNAs). Release factors mess with the enzyme that normally forms peptide bonds: they make it add a water molecule to the last amino acid of the chain. This reaction separates the chain from the tRNA, and the newly made protein is released. Translation “equipment” is very reusable. After the small and large ribosomal subunits separate from the mRNA and from each other, each element can (and usually quickly does) take part in another round of translation.
What are the stages in transcription?
Transcription is the process in which a gene’s DNA sequence is copied (transcribed) to make an RNA molecule.
RNA polymerase is the main transcription enzyme.
Transcription begins when RNA polymerase binds to a promoter sequence near the beginning of a gene (directly or through helper proteins).
RNA polymerase uses one of the DNA strands (the template strand) as a template to make a new, complementary RNA molecule.
Transcription ends in a process called termination. Termination depends on sequences in the RNA, which signal that the transcript is finished.
