protein synthesis Flashcards

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1
Q

what is a gene?

A

A sequence of nucleotide bases in a DNA molecule that codes for the production of a specific sequence of amino acids, that makes up a specific polypeptide (protein).

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2
Q

What are the two stages of protein synthesis?

A

Transcription - DNA is transcribed and an mRNA molecule is produced.
Translation - mRNA is transcribed and an amino acid sequence is produced.

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3
Q

First stage of transcription.

A

DNA helicase unzips gene by breaking hydrogen bonds between bases. DNA molecule unwinds.

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4
Q

Second stage of transcription.

A

-Free RNA nucleotides are exposed to their bases.
-Thymine is replaced with uracil.
- Free RNA nucleotides pair up with their exposed bases by complementary base pairing.

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5
Q

Third stage of transcripction.

A
  • RNA polymerase will join RNA nucleotides together to form RNA strand.
  • Joins nucleotides together by forming phosphodiester bonds, to form sugar phosphate backbone this forms mRNA.
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6
Q

fourth stage of transcription

A
  • mRNA contains the correct sequence of bases/ codon for the correct amino acid sequence.
  • mRNA leaves the nucleus through nuclear pore to travel to ribosomes (on RER) for translation.
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7
Q

What is the sense strand?

A

Runs from 5’ end to 3’ end.

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8
Q

What is the antisense strand?

A

Runs from 3’ end to 5’ end.

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9
Q

Process of translation.

A

1- mRNA binds to ribosome, and is sectioned into codons.
2- tRNA with complementary anticodon and specific amino acid binds to mRNA’S codon.
3- Another tRNA with specific amino acid binds to the next complementary codon. A tRNA molecule forms a complementary codon anti-codon complex with hydrogen bonds.
4- 1st amino acid binds to 2nd amino acid through peptide bond catalysed by peptidyl transference.
5- Ribosome moves along mRNA, releasing the first tRNA. The second tRNA becomes the first. This process continues until the ribosome reads a stop codon.

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