Week 7 - genes transcription and translation

Question 1

transcription

Answer 1

• 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

Question 2

translation

Answer 2

• 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

Question 3

transcription - process

Answer 3

• 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

Question 4

DNA transcription

Answer 4

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

Question 5

Messenger RNA: transcription

Answer 5

• single stranded

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

Question 6

Ribosomal RNA:

Answer 6

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

Question 7

Transfer RNA : translation

Answer 7

• brings AA amino acids to ribosomes for protein assembly

Question 8

translation - initiation

Answer 8

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

Question 9

tRNA & ribosomes - interaction

Answer 9

• 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

Question 10

translation elongation

Answer 10

• 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

Question 11

translation termination

Answer 11

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