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Chapter 20: Transcription
RNA differs from DNA in three ways.
1. It is ___________ stranded instead of double-stranded.
2. It has ______________ instead of deoxyribose.
3. It has ___________ (
) instead of thymine (T).
The manufacture of mRNA from a DNA template is called _______________________. It begins
when two strands of DNA unwind and separate. Only _________ strand of DNA serves as a template
for mRNA.
The enzyme ______________________________ matches RNA nucleotides with the complimentary
ones on the template strand of DNA. _____ pairs with A on the DNA.
When the mRNA is completed, ____________ bonds form again in the DNA molecule and the DNA
coils back up. The coded instructions on the ________ have now been copied to a new _________.
Chapter 21: Protein Synthesis
A protein is a chain of _____________________. The linking together of amino acids is called
__________________________ and this occurs in the _____________________ of a cell.
First the __________ leaves the nucleus through a nuclear pore after it has been transcribed from
_________. The assembly of a protein takes place on a ___________________ in the cytoplasm. A
ribosome consists of two subunits: a ____________ and a ______________.
Floating in the cytoplasm are amino acids and ___________.. Each amino acid binds to its own
specific ___________. A 3-base region on a tRNA is complementary to a 3-base region on a ______.
The three bases on a mRNA are called a _____________. The complementary three bases on a
tRNA are called an ________________________.
First, a small _________ binds to the _________ at a ___________ codon (which is AUG). A specific
tRNA carrying the amino acid methionine binds to the ________. The anitocodon on the tRNA
matches the _____________ on the mRNA. Then a large __________ subunit binds to the small
rRNA and the mRNA. A second __________ with its attached _________________________ binds
to the second codon of the __________. The first amino acid is transferred from its ________ to the
second amino acid and a covalent bond between the two amino acids is formed. The first tRNA
_____________. The ribosome moves down the mRNA to the third codon. The third codon is
recognized by the _________________ of another tRNA carrying an ____________________. The
growing protein chain is transferred to the third amino acid and the second __________ detaches.
The ribosome again moves along the _____. A ____________ is expose. Again a codon is matched
by an ________________ of a tRNA carrying an ____________________. The protein chain is
shifted, adding another _______________ to the chain. The ________ that lost its amino acid
detaches and the ribosome moves down the mRNA strand to the next codon. This process, called
___________________, builds a protein one amino acid at a time.
The sequence of amino acids in a new protein is determined by the order of bases in _______ (which
was determined by the sequence of bases in _________).
At the end of the mRNA, the ribosome encounters a _________ codon such as UGA. The completed
protein detaches. The _______ floats off. MRNA detaches from the _____________ and splits into
the small and large subunits.