Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/12

Click to flip

12 Cards in this Set

  • Front
  • Back
The sequence of events for transcription. (6)
1) RNA polymerase binds to promoter region of DNA
2) DNA double helix unwinds; one strand used as template for mRNA synthesis (Sense Strand)
3) RNA poly. moves from 3' -> 5' of DNA chain; free ribonucleotides taken up and matched to template by complementary base-paring; mRNA strand grows 5' -> 3'
4) A with U, T with A, G with C, C with G; adjacent ribonucleotides joined by phosphodiester bonds
5) RNA poly. reaches end of gene; mRNA released; DNA rewinds.
6) mRNA leaves through nuclear pores
What is required for transcription?
1) RNA polymerase
2) Free ribonucleotides:
uracil, adenine, guanine, cytosine
Where does transcription occur?
In the nucleus
What's required for translation?
1) mRNA
2) rRNA
3) tRNA (anticodon made up of a specific triplet base sequence)
4) Free amino acids
5) Ribosomes
Where does translation occur?
In cytoplasm
Describe the sequence of events for amino acid activation.
1) Enzymes involved are aminoacyl-tRNA synthetase
2) Amino acid reacts with ATP to form a.a-AMP
3) a.a.-AMP is then attached to specific tRNA molecule, to form amino acid-tRNA complex
4) Amino acid attached to the hydroxyl group of C3 of ribose of last nucleotide (A) of tRNA.
5) Aminoacyl-tRNA synthetase is specific to each of 20 amino acids
Describe the main stages of translation.
1) Binding of mRNA to ribosome
2) Initiation of polypeptide chain
3) Chain elongation
4) Chain termination
Describe the sequence of events of translation.
1) Binding of mRNA to ribosome
-Information processing region of 40S subunit binds to mRNA at 5'
-Ribosome covers 2 codons at a time
2) Polypeptide chain initiation
-Amino acid-tRNA complex with anticodon UAC binds to start codon AUG on mRNA
-a.a-tRNA complex held in 'P' site of 60S subunit
-tRNA with UAC always carries methionine; it is always the first amino acid
3) Chain elongation
-2nd a.a-tRNA complex with anticodon complementary to the second codon of mRNA binds to the latter; complex held at 'A' site of 60S
-peptide bond between first and second a.a. is formed; energy from ATP hydrolysis; catalysed by catalytic region in 60S
-Ribosome moves along mRNA to next codon
-First tRNA is released and recycled
-Second a.a-tRNA complex moves from 'A' to 'P', leaving 'A' empty for next a.a-tRNA complex with anticodon complementary to 3rd mRNA codon
-Process continues until stop codon is reached
4) Chain termination
-Polypeptide is released from the ribosome; secondary and tertiary structures assumed
-may undergo modification at Golgi
-Ribosome disassembles to subunits
-tRNA re-attached to respective a.a.
What is the role of mRNA in protein synthesis?
mRNA:
-Genetic message for synthesis of polypeptide found on DNA
-mRNA is formed from transcription of gene coding for polypeptide
-mRNA conveys genetic message from nucleus to the ribosomes
-Each mRNA has a sequence of nucleotides complementary to that of gene
-Each triplet codes for one amino acid
-mRNA codons specify the order in which amino acids are sequenced to form a polypeptide
What is the role of tRNA in protein synthesis?
tRNA:
-The CCA site at 3' end allows for attachment of an amino acid
-tRNA carries amino acid to ribosome
-Each tRNA molecule is specific—has specific anticodon, and carries corresponding amino acid
-Every codon on mRNA has a corresponding anticodon on tRNA, allows for correct sequencing of amino acids in polypeptide
What is the role of rRNA in protein synthesis?
rRNA:
-surrounds part of mRNA during protein synthesis
-holds mRNA, amino acid-tRNA complex & enzymes in precise orientation
What is the role of ribosomes in protein synthesis?
Ribosomes
-Important in translation
-Small subunit binds to mRNA
-Large subunit has 2 sites:
*'P' site for recognition of start codon, initiation of chain formation, and for formation of peptide bonds
*'A' site for holding amino acid-tRNA complex next in sequence
-Catalytic site on 60S catalyses formation of peptide bond b/w amino acids
-Many ribosomes may move along Ribosomes
-Important in translation
-Small subunit binds to mRNA
-Large subunit has 2 sites:
*'P' site for recognition of start codon, initiation of chain formation, and for formation of peptide bonds
*'A' site for holding amino acid-tRNA complex next in sequence
-Catalytic site on 60S catalyses formation of peptide bond b/w amino acids
-Many ribosomes may move along mRNA at same time to increase rate of translation