Protein synthesis Flashcards
Transcription of gene- in the nucleus…
a complimentary copy of each gene from the sense strand of DNA is made by building messenger mRNA.
How is the mRNA molecule made?
Three RNA nucleotides are joined together by RNA polymerase. This process copies the DNA code onto an mRNA molecule.
When does the transcription of gene starts and ends?
When RNA polymerase binds to a control region of the DNA called promoter. It ends when the enzyme reaches a terminator sequence.
When RNA polymerase reaches the terminator sequence, it stops…
adding nucleotides to the growing mRNA.
When the process of transcription is finished, the hydrogen bonds…
holding the DNA and RNA together are broken and double-stranded DNA reforms.
The last triplet transcripted onto mRNA is…
one of the DNA triplets coding for stop.
Types of terminator sequence:
ATT, ATC or ACT
Translation is the process of…
translating the DNA code into an amino acid sequence.
The mRNA leaves the nucleus by…
the pores in the nuclear envelope and attaches to ribosomes in the cytoplasm.
tRNA can be found in…
cytoplasm.
tRNA stands for…
transfer RNA.
tRNA has…
triplet bases at one end and a region where an amino acid can attach at the other.
There are more than 20 different…
tRNA molecules, each with a particular triplet of bases and region able to attach to a specific amino acid.
The tRNA bonds with their specific…
amino acid from the cytoplasm, under the control of a specific enzyme and with energy from ATP.
The triplet bases of tRNA are called…
anticodon.
The triblet bases of mRNA are called…
codon.
The anticodon of tRNA links up…
with complementary codon of the mRNA molecule.
Two tRNA molecules fit onto…
the ribosome at the same time. This brings two amino acids together and a peptide bond is formed.
Usually, several ribosomes work on the same…
mRNA strand at the same time.
Polyribosomes are…
several ribosomes working on the same mRNA at the same time.
To start transcription the DNA must…
unwind and unzip first.
The base sequence of DNA determines…
the base sequence of mRNA, which determines which tRNA molecules can link up with them.
Each tRNA molecule is specific for…
just one amino acid. This determines the sequence in which amino acids are linked together.
When the DNA is unzipped and unwind, complementary…
activated RNA nucleotides pair up with exposed DNA bases.
The sugar-phosphate groups are bonded by…
RNA polymerase to form the sugar-phosphate backbone.
The tRNA brings…
the amino acid to the mRNA molecule at the ribosome.
Ribosomes are made of…
ribosomal RNA (rRNA) and protein. They contain large and small subunit.
The mRNA binds to…
the small subunit.
6 bases of mRNA at a time are exposed to…
a large subunit.
Peptidyl transferase catalysis…
the formation of a peptide bond between amino acids. The enzyme is found in the small subunit of the ribosome.
The ribosome has 3…
active sites. E, P and A
At P site…
peptide bonds are formed. Also, the first tRNA enters the P region first.
The second tRNA enters…
the A active site and peptide bond forms between the two amino acids.
The tRNA from P active sites moves to…
E active site and loses the amino acid attached to it. This builds up the amino acid chain.
When a stop codon is…
exposed, the process of synthesis stops.
