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Biology 311C > Transcription & Translation (4) > Flashcards

Transcription & Translation (4) Flashcards

1
Q

gene

A

linear segment of dna that contains the information needed to synthesize or “express” a particular gene product (rna or protein)
- made up of dna
- codes for rna and proteins

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2
Q

What are the two steps of protein expression?

A
  1. transcription of mRNA from DNA
  2. translation of mRNA to produce a polypeptide chain
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3
Q

Transcription relies on …

A

complementary base-pairing to copy the nucleotide sequence information present in one strand of the double helix

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4
Q

Messenger RNAs are processed prior to translation …

A

in eukaaryotic cells this involves the removal or splicing of introns

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5
Q

Where does translation take place?

A

In ribosomes, and relies upon a highly conserved genetic code

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6
Q

What are mutations?

A
  • changes in the genetic information encoded in dna
  • can change the sequence of amino acids in the protein formed from the mutated gene
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7
Q

Central dogma proposed by Francis Crick

A

DNA (transcription) RNA (translation) Protein

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8
Q

What direction is RNA synthesized in?

A

5’ to 3’ direction

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9
Q

How is RNA synthesized?

A

By an RNA polymerase from a DNA template

needs
- nucleoside triphophates (NTP)
- Mg at suitable conditions

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10
Q

Does RNA polymerase need a primer?

A

No

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11
Q

RNA polymerase works with …

A
  • other proteins called trans-acting factors/transcription factors
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12
Q

Transcription factors recognize …

A
  • cis-acting elements (specific sequences on theDNA)
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13
Q

What do cis-acting elements include and what can they do?

A
  • promoter
  • suppresor
  • enhancer

they can affect the amount, rate, and accuracy of the transcription

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14
Q

The promoter in eukaryotes affects the …

A

accuraty and amount of transcription

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15
Q

What the enhancers and suppresors called and what do they do?

A
  • Regulatory regions
  • when bound by transcription factors result in more active or less active transcription
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16
Q

What happens when the RNA polymerase and ____ bind to the promoter?

A
  • transcription factors
  • open the double helix and start transcribing RNA by incorporating NTPs (C U A G) complimentary to the template RNA strand.
  • the opposite strand is not transcribed
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17
Q

Where does transcription stop?

A

the transcription stop site

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18
Q

What the the transcription stop site denoted by in eukaryotes?

A

the sequence AATAAA

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19
Q

What does RNA polymerase I transcribe?

A

ribosomal RNA (rRNA)

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20
Q

What does RNA polymerase II transcribe?

A

messenger RNA (mRNA)

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21
Q

What does RNA polymerase III transcribe?

A

transfer RNA (tRNA) and one type of rRNA

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22
Q

Where is eukaryotic RNA processed and translated?

A

processed in the nucleous, translated in the cytoplasm

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23
Q

Major type of processing 1: Capping & Polyadenylation

A

Capping happens and at the 3’ end a stretch of poly-As (adenines) is added by an enzyme poly(A) polymerase

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24
Q

Capping process

A

the phosphate group of a modified form of guanosine triphosphate (GTP) is added to the 5’ end of RNA

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25
Q

What does capping do?

A
  • protects mRNA
  • marks the 5’ ends as the starting point for translation
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26
Q

What RNAs are capped and polyadenylated?

A

only mRNA, to increase their stability

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27
Q

polyA+RNA is …

A

not found in prokayotes

28
Q

RNA processing: Splicing

A

During splicing introns are removed and exons are are joined together

almost all eukaryotic RNA undergo splicing and other processing, except genes that lack introns

29
Q

Introns:

A

intervining sequences that do not code for a protein

30
Q

Exons:

A

expressed regions coding for a protein or a segment of a protein

31
Q

What does NTR refer to?

A

non-translated regions present in processed RNA at 5’ and 3’ ends, that do not code for a protein

32
Q

Autocatalytic RNA

A

rna that splice themselves

33
Q

Splicesome

A

in some RNA splicing occurs in this complex, made up of small nuclear RNAs, small nuclear ribonucleproteins, and other proteins

34
Q

George Beadle and Edward Tatum

A

generated mutations of a fungus so it could not grow on a minimum medium

  • one enzyme is coded by one gene
  • any mutations is a gene will result in a mutated enzyme
35
Q

one gene …

A

one enzyme or one polypeptide

36
Q

How is information communicated from DNA to protein

A
  • dna is first transcribed into mRNA which is translated into proteins using adapters (tRNA) using a coding system (codons)
37
Q

Why are codons used?

A

Codons/coding systems are used because DNA and RNA only have 4 bases, but protein has 20 amino acids

38
Q

___ bases code for ___ amino acid(s)

A

3 bases code for 1 amino acid, so 64 amino acids are possible

39
Q

Start codon (starts polypeptides)

A

AUG

40
Q

Stop codons

A

UGA, UAG, UAA

41
Q

degeneracy

A

multiplicity or redundancy of codons coding for one amino acid

  • some amino acids were coded by more than one codon
42
Q

What are the three types of mutations?

A
  • point mutations
  • insertions or deletions
  • inversion or translocation
43
Q

Point mutations

A
  • single base paire is changed or substituded with another
  • if this mutation results in a different amino acid it is called a missense mutation
  • if the change resulted in in the protein sequence stopping it is called a nonsense mutation
44
Q

Insertions or Deletions

A
  • one or more bases are inserted or deleted resulting in a frameshift mutations
  • can happen at the chromosomal level
45
Q

Inversion and Translocation

A
  • two segments of a chromosome can be inverted or translocated
46
Q

Mutagenesis; what can cause mutations?

A
  • natural
  • chemical mutagens
  • physical mutagens
47
Q

Where does protein synthesis occur in eukaryotic cells?

A

in the cytoplasm

48
Q

Transfer RNA

A
  • acts as an adapter between mRNA and ribosomes during protein synthesis
  • different types specific to the amino acids
  • amino acids are activated and attached at the 3’ region
  • have an anticodon complementary to the codon in mRNA
49
Q

Inosine:

A

sometimes the third base in tRNA, can recognize A, U, or C on mRNA

modified form of Guanine

50
Q

Wobble

A

flexibility of the third base to bond with more than one codon

51
Q

rRNA

A
  • major component of ribosomes
  • most abundant RNA
  • couple the mRNA and tRNA carrying various amino acids
  • make peptide bonds between amino acids to make proteins
52
Q

mRNA

A
  • carries message from the gene to be translated into protein
  • has a poly(A) tail and travels cytoplasm to be translated
  • processed mRNA carry regions that are recognized by ribosomes to start to protein synthesis
  • translation starts with the AUG codon
53
Q

Amino Acid Activation

A
  • ## amino acids must be activated and attached to the 3’-OH group of tRNA to transfer to the elongating polypeptide
54
Q

Enzymes in Amino Acid Activation

A
  • aminoacyl-tRNA synthetases
  1. binds to right amino acid at its -COOH terminus and attached an AMP by hydrolyzing ATP
  2. the enzyme recognizes the tRNA by its secondary structure and anticodon
  3. it then transfers the amino acid to the 3-OH group of the correct tRNA and the AMP is detached. then it releases the aminoacyl-tRNA
55
Q

What are the three stages of protein synthesis?

A

Initiation, elongation, and termination

56
Q

Initiation

A
  • subunit of ribosomes recognize the ribosome binding site at the 5’ NTR
  • special tRNA binds to the P-site
  • 3 initiation factors (proteins) and GTP bind to form initiation complex
  • large subunit joins with the small subunit and initiation complex
  • GTP is hydrolyzed in this step
57
Q

What are the three steps of elongation?

A
  1. Codon recognition
  2. Peptide bond formation
  3. Translocation
58
Q

Codon recognition

A

Elongation factor [EF (proteins)] brings aminoacyl tRNA and places it on the A site. GTA attached to EF is hydrolyzed

59
Q

Peptide bond formation

A
  • peptidyl transferase activity of ribosomes transfers methionine (growing polypeptide) from P-site tRNA to A-site and makes a peptide bond between the carboxyl terminus of previous amino acid and amino terminus of incoming amino acid
  • tRNA at P-site moves from P-site to E-site (exit) and leaves ribosome
60
Q

Translocation

A

-tRNA at A-site translocated to to P-site, another GTA is hydrolyzed
- mRNA codons and corresponding tRNA are H-bonded
- now the next codon moves to the A-site

61
Q

Termination

A
  • polypeptide elongation continues until the stop codon on mRNA reaches the A-site
  • release factor protein binds to stop codon and makes peptidyl transfease add H2O to growing polypeptide chain
  • releases completed polypeptide from tRNA at P-site and from the ribosome
  • ribosome subunits separate and go on to start another polypeptide synthesis
62
Q

Polysome

A

one mRNA can be translated simultaneously by several ribosomes making several polypeptides from one template

63
Q

What are the examples of protein processing?

A
  • zymogen activation
  • disulfide bonds
  • hydroxylation
  • glycosylation and myristylation
64
Q

Zymogen activation

A

inactive protein that becomes active after processing

65
Q

Disulfide bonds

A

formed between two cysteines

66
Q

Hydroxylation

A

some amino acid chains are chemically modified

67
Q

Glycosylation and myristylation

A

.. of some residuals on the protein occur in the golgi apparatus

Biology 311C (10 decks)

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