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Cell Developmental Biology > Lecture 5-Translation > Flashcards

Lecture 5-Translation Flashcards

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1
Q

In which direction is the mRNA strand read? And how is the polypeptide chain synthesized?

A
  • mRNA strand is read from the 5’ to 3’ direction.

- Amino acids are synthesized from the amino to carboxy terminus

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2
Q

What are the N-terminal and C-terminal, where are they located? Are they part of the amino acid polypeptide?
What is structural polarity mean?

A
  • The N-terminal is usually on the left side of the polypeptide strand (NH2).
  • The C-terminal strand is found on the right side of the amino acid polypeptide strand (COOH).
  • Each polypeptide has structural polarity where the N-terminal end is positive (+) while the C-terminal end is negative (-).
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3
Q

What is the beginning and end of the polypeptide chains called?

A
  • The beginning of the peptide chain is the N-terminus while the end of the chain is the C-terminal.
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4
Q

What is the adaptor hypothesis and who invented it?

A
  • The adaptor hypothesis by Francis Crick what used to explain how information from nucleic acids was able to translate into a specific amino acid sequence.
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5
Q

How does tRNA play a role in translation? Codon and Anticodon?

A
  • tRNA uses its 3 base pair anti-codon sequence which is complementary to the 3 base pair codon on the mRNA strand to create polypeptide strands.
  • The anti-codon codes for a specific amino acid.
  • In conjunction, these amino acids form polypeptide strands.
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6
Q

What molecule pairs and binds an amino acid to its tRNA?What is the tRNA/amino acid complex called?

A
  • Aminoacyl- tRNA Synthetases makes sure the correct amino acid is bound to its tRNA.
  • This is called a charged tRNA.
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7
Q

Is the genetic code universal? Do multiple codons code for a single amino acid?

A
  • The genetic code is pretty much universal and there are many codons that code for a single amino acid.
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8
Q

What is wobble base pairing?

A
  • Wobble base pairing is a pair between nucleotide bases that do not follow the original complementary rule.
    Ex. G-U or I-C
  • This base pairing usually occurs in the 3rd positional base in the codon.
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9
Q

What is the structure of the ribosome in Eukaryotes? What is the ribosome considered? Which subunit is each one?

A
  • The ribosome in eukaryotes is made from 2/3 rRNA (large subunit) and 1/3 protein (small subunit).
  • The ribosome is considered a ribozyme.
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10
Q

What are the three areas of the ribosome? Where are they relatively located?

A
  1. ) Polypeptide chain exit tunnel- found at the top of the ribosome complex.
  2. ) Peptidyl Transferase Center- Site where amino acid gets bonded to the polypeptide chain. - found in the P/A sites.
  3. ) Decoding site- Monitors the interaction between the anti-codon and codon- found where these two sites bind in the ribosome.
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11
Q

Where is the ribosome bind to?

A
  • The translation start site.
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12
Q

What dictates the reading frame of mRNA? And usually hoe many possible reading frames are there?

A
  • The translation start site sequence determines the reading frame.
  • There is always a possibility of three reading frames.
    Ex.) CUC or CU or C
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13
Q

In prokaryotes, can transcription and translation occur simultaneously? How many amino acids are translated per second? Do they occur in the same direction?

A
  • Yes, prokaryotes can transcribe and translate simultaneously and they translate about 20 amino acids per second.
  • They occur in the same direction because transcription occurs from 5’ to 3’ mRNA while translation is read from the 5’ to 3’ direction.
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14
Q

In prokaryotes, how does the ribosome know where to bind? Which subunit is complementary to this site?

A
  • The Shine-Dalgarno Sequence is where the start codon for the ribosome to bind to is located.
  • This sequence is complementary to the small subunit on the ribosome. The small subunit binds here. This allows the mRNA and ribosome to bind.
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15
Q

In which site does the first tRNA bind to, to start the polypeptide chain?

A
  • The first tRNA binds to the P-site in the ribosome.
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16
Q

Which organisms mRNA is monocistronic vs. polycistronic? What do these 2 things mean?

A
  • Eukaryotic mRNA is monocistronic while prokaryotes have polycistronic mRNA.
  • Monocistronic mRNA means that the mRNA strand can only code for 1 protein -> it only has one gene.
  • Polycistronic means the mRNA strand can code for multiple proteins -> it has multiple genes.
17
Q

How does transcription initiation occur in Eukaryotes?

A
  1. ) Translation initiation factor binds to the small subunit of the ribosome.
  2. ) This complex then binds to the mRNA strand and starts searching for the start codon (5’ -> 3’) direction.
  3. ) Once the start codon is found, the translation initiation factor disassociates and the large ribosomal subunit binds forming the ribosome.
  4. ) First charged tRNA binds to the P-site
  5. ) The second tRNA then binds to the A-site and the first amino acid bond is formed.
18
Q

What is aminoacyl-tRNA and what is another name for it? What is its function?

A
  • Aminoacyl-tRNA is a charged t-RNA which carries the amino acid to the ribosome for binding.
19
Q

Where is the polypeptide strand held and where does it move to? P/A site?

A
  • The polypeptide strand is held in the P-site but transferred to bind with the amino acid in the A-site until the ribosome moves to the right and now the polypeptide strand is in the P-site again.
20
Q

From which terminal is the polypeptide strand grow to and from?

A
  • The polypeptide strand has an open C-terminal, so the charge t-RNAs amino acid uses its N-terminal to bind the C-terminal of the growing polypeptide strand.
21
Q

How does the ribosome move along the mRNA strand? Think subunits.

A
  • First, the large subunit translocated down the mRNA strand.
  • Then the small subunit translocates down the mRNA strand.
22
Q

How does translation stop? Describe the process.

A
  • Translation stops when a stop codon is found in the A-site of the ribosome.
  • No tRNA can bind to the stop codon so a release factor binds to this codon, which releases the polypeptide chain and then the ribosome dissociates.
23
Q

What are polyribosomes?

A
  • Polyribosomes are mRNA with multiple ribosomes translating the strand simultaneously.

Cell Developmental Biology (5 decks)

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