Protein Synthesis- transcription and translation

A simple description of protein synthesis and a little quiz to test you. Hope it helps...

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I hear you're a little confused about protein synthesis, eh? Don't worry about it, sit back, read and
1. Transcription- takes place in the nucleus
DNA molecule unwinds and unzips
The two strands separate
A mRNA (a messenger RNA which is a single-stranded
molecule) forms next to the coding strand, using it as a
Complimentary base pairing occurs where cytosine and
guanine match up and adenine and uracil match up.
NB- notice how in DNA adenine and thymine match up
The mRNA exits the nucleus through the nuclear pore (a gap in
the nuclear membrane)
2. Translation- takes place in the cytoplasm
The mRNA code is read by the ribosome (another organelle in
a cell)
A tRNA (a transfer RNA) brings amino acids to the mRNA
where they also match up with complimentary base pairing.
Each amino acid has 3 bases on it- a codon.
NB- there are only 20 amino acids that exists and they code for
all proteins!
Several amino acids build polypeptides.
Several polypeptides make proteins... FINALLY!!!
3. QUIZ- gap-fill exercise
Transcription is the first stage in protein ________. When a gene is activated, part of the DNA
double________ unwinds, and the base________separate. The________ strand acts as a ________ to
form a single-________ molecule of mRNA. mRNA has four bases, A, C, G and ________. When the
mRNA is complete it breaks away from the DNA and leaves the nucleus through a _______ in the
nuclear membrane. It then travels to a ________ in the cytoplasm. Parts of the cell, such as the
nucleus, are called ________.
The completed strand of mRNA, carrying the genetic code from the DNA, leaves the nucleus and
enters the ________. The mRNA links to a ________, carrying the genetic code from the ________.
The ________moves along the mRNA strand `reading' the code. A chemical called tRNA brings amino
acids to the mRNA. The triplet of ________ on the tRNA matches up with a triplet ________on the
mRNA. The two amino acids are joined together by a chemical ________. One by one a chain of amino
acids is built up, forming a ________. This long chain of amino acids will fold to form a working protein,
such as the hormone called ________.


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