Genetic Control of Protein Structure and Function.

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Describe 4 features of the genetic code?
It is universal (same code for amino acids in all organisms), it is degenerative (most amino acids coded for by more than one codon), it is non-overlapping (each codon is read only once), and some amino acids only have a single codon.
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Where is DNA stored in a cell?
In the nucleus.
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Why can't proteins be produced in the nucleus?
Because proteinsynthesis takes place in the cytoplasm where the RER and SER are, DNA is too large to leave the nucleus through the nuclear pores.
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What are the two types of rybonucleic acid?
mRNA (messenger RNA), and tRNA (transfer RNA)
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Describe the structure of mRNA?
It is a long strand that is arranged into a SINGLE helix.
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Why is mRNA useful?
Because it is a copy of a strand of DNA and it is able to leave the nucleus through nuclear pores as it is small.
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How does the structure of mRNA support it's function?
It posesses the correct sequences of the many triplets of organic bases that code for specific polypeptides.
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What are the organic bases in mRNA?
Adenine, Cytosine, Guanine and Uraci (Uracil
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What is tRNA?
Transfer ribonucleic acid.
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Describe the structure of tRNA?
It is a single stranded molecule folded into a clover-leaf shape, with one end of the chain extending out more than the other. Each is able to carry a single amino acid, at the opposite end of the tRNA is a sequence of 3 bases called the anti-codon.
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What is transcription?
The process of making pre-mRNA from DNA molecules.
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What does the enzyme DNA helicase do to DNA?
DNA helicase acts on a specific molecule to break the H-bonds between bases, causing the 2 strands to seperate and expose the nucleotide bases in that region.
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What does DNA polymerase do to DNA?
RNA polymerase moves along one of the two DNA strands known as the TEMPLATE strand, causing the nucleotides on this strand to join with the individual complementary nucleotides from the pool that is present in the nucleus.
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What happens as RNA polymerase reaches the particular sequence of bases that it recognises as a 'stop' codon?
It detaches and the production of pre-mRNA is complete.
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What is splicing?
It is removing the introns from pre-mRNA before it enters the cytoplasm.
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Why is pre-mRNA spliced?
Because if the mRNA contains introns then this may result in the production of a faulty polypetide.
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What is the next step after transcription in polypeptide synthesis?
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What happens after mRNA has passed out of the nuclear pore and into the cytoplasm?
A ribosome attaches to the starting codon on the mRNA sequence.
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What happens once a ribosome has attached to the starting codon of the mRNA sequence?
The tRNA with the complimentary anticodon sequence moves to the ribosome and pairs up with the complimentary sequence on the mRNA.
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What does tRNA carry?
An amino acid.
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What happens to the amino acids as more tRNA attaches to mRNA?
They form peptide bonds, eventually forming a polypeptide chain.
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How are the amino acids joined by a peptide bond?
Through the use of an enzyme and ATP.
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What happens when tRNA reaches a 'stop' codon?
The ribosome, mRNA and the last tRNA molecule all separate and the polypeptide chain is complete.
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Card 2


Where is DNA stored in a cell?


In the nucleus.

Card 3


Why can't proteins be produced in the nucleus?


Preview of the front of card 3

Card 4


What are the two types of rybonucleic acid?


Preview of the front of card 4

Card 5


Describe the structure of mRNA?


Preview of the front of card 5
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