Explain the process of
transcription and translation that involved in protein synthesis.
Answer:
Transcription
-RNA polymerase with the help of
sigma factor recognizes and binds to promoter. It moves along DNA in the 3’ to
5’ direction and breaking the hydrogen bonds. Double helix separates. Since the
transcription is initiated, the sigma factor will detach from DNA. RNA
polymerase catalyses correct base pairing: A with U, C with G. The correct
paired bases will then be linked together. When RNA polymerase reached
terminator, mRNA synthesized will form a hairpin loop structure. The DNA, mRNA
and RNA polymerase detach. DNA broken by DNA polymerase previously is coiled
into helix again.
Transcription in eukaryotic cells
-Transcription in eukaryotic cells
produce pre-mRNA. Pre-mRNA contains introns and exons. Introns are the
sequences that code for nothing while the exons contain gene. Spliceosome
splits the introns. The exons join to form mature mRNA. That is not exist in
Prokaryotic cells.
Translation
-Ribosome divides into large
ribosomal subunit and small ribosomal subunit. The large subunit has three
sites: A site, P site and E site. First, a small ribosomal subunit binds to a
mRNA molecule. An initiator aminoacyl-tRNA with the anticodon UAC base paired
with the start codon AUG. Large ribosomal subunit is added to the small subunit
to form a functional ribosome. Then another tRNA that recognizes the next codon
will carry the second amino acid to A site. A peptide bond is formed between
two adjacent amino acids. The ribosome moves along the mRNA by one codon. The
tRNA that carried UAC is released at E site and the second amino acid that
carried by its tRNA is moves into P site.. A tRNA carrying the next amino acid
now moves into A site. Again, the amino acid formed previously joined to amino
acid at A site by peptide bond. When the ribosome meets terminator, large
subunit, small subunit, mRNA and the protein formed are released.
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Transcription
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Translation
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-synthesis
of mRNA
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-synthesis
of protein(a polypeptide)
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-occur
in nucleus
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-occur
in cytoplasm
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-sigma
factor, RNA polymerase and DNA
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-ribosome(large
subunit=small subunit), amino acid-tRNA complex and mRNA
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*Ribosomal RNA-structural component
of ribosomes (synthesized in nucleolus)
*Transfer RNA-a molecule that carries
base anticodon complementary to codon on mRNA (transfer amino acids in
cytoplasm to the ribosome)
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