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A.P. BIO > Steps of Transcription and Translation > Flashcards

Steps of Transcription and Translation Flashcards

1
Q

Three steps of transcription

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

When does transcription begin?

A
  • RNA polymerase molecules attach to a promoter region of DNA
    *Promoter regions upstream of the desired gene to transcribe
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3
Q

Eukaryotes transcription

A

-Promoter region is called TATA box
-Transcription factors help RNA polymerase bind

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4
Q

Prokaryotes transcription

A

-RNA polymerase can bind directly to the promoter

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5
Q

1st step DNA elongation transcription

A

RNA polymerase opens the DNA and reads the triplet code of the template strand
*moves in the 3’ to 5’ direction
*mRNA transcript elongates 5’ to 3’

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6
Q

2nd step DNA elongation transcription

A

*RNA polymerase moves downstream, only opens small sections of DNA at a time
*Growing mRNA strand peels away from the DNA template strand. DNA double helix then reforms
*Single gene can be transcribed simultaneously by several RNA polymerase molecules
-Helps increase the amount of mRNA synthesized
-Increases protein production.

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7
Q

Termination in prokaryotes

A

-Transcription proceeds through a termination sequence
-Causes termination signal
-RNA polymerase detaches
-mRNA transcript is released and proceeds to translation
-mRNA does not need modifications

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8
Q

modifications for pre-mRNA before translation

A
  1. 5’ Cap
  2. Poly-A-tail
  3. RNA splicing
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9
Q

5’ cap (GTP)

A

5’ end of pre-mRNA receives a modified guanine nucleotide “cap”

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10
Q

poly-A-tail

A

3’ end of the pre-mRNA receives 50-250 adenine nucleotides

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11
Q

Poly-A-tail and 5’ cap function to:

A
  1. Help the mature mRNA leave the nucleus
  2. Help protect the mRNA from degradation
  3. Help ribosomes attach to the 5’ end of the mRNA when it reaches the cytoplasm
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12
Q

RNA splicing

A

Sections of the pre-mRNA, called introns, are removed and then exons are joined together

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13
Q

Introns

A

intervening sequence, don’t code for amino acids

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14
Q

Exons

A

expressed sections, code for amino acids

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15
Q

Why does splicing occur?

A

a single gene can code for more than one kind of polypeptide , known as alternative splicing

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16
Q

Translation

A
  1. The synthesis of polypeptides using info from the mRNA
  2. Occurs in the ribosome
  3. Nucleotide sequence becomes an amino acid sequence
  4. tRNA is a key player in translating mRNA to an amino acid sequence
17
Q

Transfer RNA

A
  1. tRNA has an anticodon region-complementary and antiparallel to mRNA
  2. tRNA carries the amino acid that the mRNA codon codes for
  3. Enzyme aminoacyl-tRNA synthetase responsible for attaching amino acids to tRNA
    -when a tRNA carries an amino acid its “charged”
18
Q

Ribosomes and translation

A

-Translation occurs at the ribosome
-ribosomes have two subunits: small and large
-Prokaryotic and eukaryotic ribosomal subunits differ in size

19
Q

The large subunit has three sites

A

A site: amino acid site, holds the next tRNA carrying an amino acid
P site: polypeptide site
-holds the tRNA carrying the growing polypeptide chain
E site: Exit site

20
Q

How does the tRNA interact with the mRNA?

A

anticodon and codon interactions

21
Q

Translation 3 steps

A
  1. Initiation
  2. Elongation
  3. Termination
22
Q

Elongation translation

A

-The next tRNA comes into the A site
-mRNA moved through ribosome and its codons are read
-each mRNA codon codes for a specific amino acid

23
Q

When does translation begin? (initiation)

A

When the small ribosomal subunit binds to the mRNA and a charged tRNA binds to the start codon, AUG, on the mRNA
-tRNA carries methione
-next the large subunit binds

24
Q

Elongation translation steps

A
  1. Codon recognition- appropriate anticodon of the next tRNA goes to the A-site
  2. Peptide bond formation-Peptide bonds are formed that transfer the polypeptide to the A-site
  3. Translocation- tRNA in A site moves to the P and then to the E site.
25
Q

Since all organisms use the same genetic code, it supports the idea of

A

common ancestry

26
Q

Termination in translation

A

-occurs when a stop codon in the mRNA reaches the A site of the ribosome
-Stop codon signals for a release factor
*hydrolyzes the bond that holds the polypeptide to the P site
*polypeptide releases
*all translational units disassemble

27
Q

Protein folding

A

-Genes determine the primary structure which determines the final shape
-Some proteins require chaperone proteins or modification before it can be functional in the cell.

28
Q

Retroviruses

A

-HIV exception to the standard flow of genetic information
-Info flows from RNA to DNA

A.P. BIO (28 decks)

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