Week 7 - genes transcription and translation Flashcards Preview

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Flashcards in Week 7 - genes transcription and translation Deck (11)
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1

transcription

- produces an RNA copy or transcript of gene
- genes produce messenger RNA (mRNA) that species the amino acid sequence of a polypeptide/functional/ structural RNA species
- DNA used to synthesise RNA. exact wording except U vs TRNA vs DNA

2

translation

- process of synthesising a specific polypeptide on a ribosome
- mRNA used to direct synthesis of polypeptide: translation since making a polypeptide req. translation of nucleic acid language to protein language

3

transcription - process

- DNA used as template to make RNA
- accomplished by RNA POLYMERASE & follows base - pairing rules

Process: occurs in nucleus (eukaryotes)
- RNA polymerase separates the two strands of DNA
- only one of two strands will be used to create RNA
- oirder of bases in DNA is genetic info that codes protein
- order of AA in protein is determined by order of nucleotides in DNA

4

DNA transcription

1. DNA helix unzipes
2. one of two DNA strands act as a template
3. RNA nucleotides line up along one strand f the DNA following base-pair rules. RNA polymerase produces the mRNA strand using DNA as a template
4. RNA has U not T at corresponding position in DNA
5. RNA polymerase forms covalent bonds between nucleotides
6. transcription continues until one entire gene is converted to RNA
7. single stranded messenger RNA separates & DNA strands rejoin by base pairing

5

Messenger RNA: transcription

- single stranded
- in eukaryotic cells- mRNA is transported from nucleus to cytoplasm →direct making of proteins

6

Ribosomal RNA:

- structural & functional component of ribosomes w/ proteins that also form part of ribosome

7

Transfer RNA : translation

- brings AA amino acids to ribosomes for protein assembly

8

translation - initiation

Small ribosomal subunit BINDS TO BEGINNING OF Mrna & seaches for AUG start codon

a tRNA brings first AA
- anticodon in the tRNA matches w/ a codon of mRNA
- each tRNA carries a specific AA based on anticodon
- start codon, AUG binds to tRNA that carries a methionine

large ribosomal unit joins complex * next step, translation elongation can proceed

9

tRNA & ribosomes - interaction

- P site: binds tRNA attached to the growing peptide chain
- A site : binds tRNA carrying next AA
- E site: binds tRNA that carried last AA

10

translation elongation

- next tRNA binds w/ next codon on the mRNA
- the ribosomes add this amino acid to growing polypeptide
- ribosomes moves down to next codon
- process repeats, for each step, new AA is added to protein
- peptide bonds are formed between a ' new ' charged tRNA in 'A site and the growing chain attached to tRNA in 'P' site

11

translation termination

Elongation continues until ribosome encounters a STOP CODON: UAA, UAG, UGA

A release factor binds to the stop codon
- causes ribosome to release polypeptide
- ribosomal subunits separate and release mRNA
- mRNA can be translated again by another ribosome