Biology 1.2 Transcription and Translation Flashcards

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1
Q

What is a gene?

A

A gene is a section of DNA that codes for a specific protein or RNA

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2
Q

Introns and Exons

A

DNA contains both coding sequence and non-coding sequnce. Exons: coding DNA. Introns: non-coding DNA.

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3
Q

DNA to Protein

A

Step 1: Transcription
Step 2: Splicing
Step 3: Translation

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4
Q

Steps of Transcription

A
  1. DNA is unzipped at a specific gene
  2. RNA polymerase uses free RNA nucleotides to synthesise an RNA copy of the specific gene.
  3. The whole gene is copied, including non-coding introns.
  4. After copying, the DNA is zipped up again.
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5
Q

Transcription

A

Occurs in the nucleus of eukaryotic cells. The template strand is copied. The RNA produced will be processed to form a mRNA. mRNA takes a copy of the gene code to the cytoplasm.

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6
Q

Splicing

A

After a gene is transcribed from DNA, the non-coding introns must be removed. An RNA enzyme complex called a spliceosome brings exon ends together and cuts out the introns. The final mRNA contains only coding sequences, ready for translation in the cytoplasm.

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7
Q

Codons and Amino Acids

A

A gene is specific sequence of nucleotides in DNA. A group of three nucleotides is a codon. One codon codes for one amino acid. The sequence of codons codes for a specific sequence of amino acids in a polypeptide.

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8
Q

Translation

A

In the cytoplasm, a ribosome assembles around the mRNA. Specific amino acids are carried to the ribosome by transfer RNAs. The anticodon on a tRNA is complementary to a codon on the mRNA. Amino acids are joined to form a polypeptide.

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9
Q

3 key step of translation

A
  1. Initiation
  2. Elongation
  3. Termination
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10
Q

Translation - Initiation

A

All genes start with an AUG codon. The initiator tRNA with a UAC anticodon binds to the mRNA. The ribosome subunits assemble at this location.

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11
Q

Translation - Elongation

A

The next tRNA enters the ribosome, bringing a specific amino acid. A peptide bond forms between the first and second amino acids. The ribosome moves to the next codon, the first tRNA is released and the process repeats.

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12
Q

Translation - Termination

A

Elongation continues until the ribosome reaches a STOP codon. STOP codon do not code for an amino acid. Instead, they recruit a release factor to disassemble the ribosome and release the polypeptide.

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