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BIOLOGY 130 > Unit 5 - Gene Expression > Flashcards

Unit 5 - Gene Expression Flashcards

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1
Q

Central Dogma of Molecular Biology

A

DNA is transcribed into mRNA, which is then translated to amino acids which synthesis to form a protein (polypeptide chain)

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2
Q

mRNA

A

codes for proteins

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3
Q

rRNA

A

forms core of ribosome and catalyzes protein synthesis

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4
Q

miRNA

A

regulates gene expression

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5
Q

tRNA

A

serves as adapter between mRNA and amino acids during protein synthesis

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6
Q

template strand

A

strand of DNA which is transcribed

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7
Q

coding strand

A

matches RNA, except U of RNA is T of DNA

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8
Q

RNApol (prokaryotic)

A
  • large, globular enzyme with several channels running through it
  • active site at intersection of channels
  • holoenzyme with core enzyme (synthesizes RNA) and regulatory subunit (sigma factor)
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9
Q

Sigma Factor

A
  • recognizes promoter sequence
  • most bacteria have several types of sigma proteins
  • each sigma binds to promoters with slightly different sequences
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10
Q

Initiation of Transcription in Prokaryotes

A
  • initiated at promoters, regions on non-template strand:
    1. -10 box 2. -35 box
  • transcription begins when sigma identifies and binds to promoters
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11
Q

Termination of Transcription in Prokaryotes

A
  • RNApol reaches transcription termination signal in DNA template
  • codes for RNA that folds back on itself, forms hairpin structure
  • hairpin disrupts transcription complex
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12
Q

RNApol 1

A

transcribes most rRNA genes

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13
Q

RNApol 2

A

transcribes protein-coding genes, miRNA genes, genes of small RNAs

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14
Q

RNApol 3

A

transcribes tRNAs

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15
Q

Start of Transcription in Eukaryotes

A
  • TATA binding protein (TBP) recognizes promoter sequence

- TBP+TFIID distort helix, allows other factors to pile and form the ‘transcription initiation complex’

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16
Q

mRNA processing

A
  • 5’ cap
  • 3’ poly (A) tail
  • 5’ cap and 3’ tail are marked by proteins
  • Exon junction complexes (EJC) bind to properly spliced mRNAs and transport them out of the nuclus
17
Q

spliceosomes

A
  • 5 small nuclear ribonucleic particles (snRNPs)

- catalytic activity provided by RNA component –> ribozymes

18
Q

How are introns spliced out?

A
  1. Branch point A attacks 5’ splice cite and cuts the sugar-phosphate backbone
  2. cut end forms a covalent bond with the ribose sugar group
  3. lariat structure is degraded
19
Q

Advantage of RNA splicing

A

-creates different proteins from same gene/same primary mRNA transcript depending on cell type

20
Q

Disadvantages of RNA splicing

A
  1. more steps = more work

2. more opportunity for error

21
Q

Genetic code exception

A

-assigning some of STOP codons to amino acids instead, usually in mitochondria

22
Q

aminoacyl tRNA

A

-formed from tRNA, amino acid, and aminoacyl tRNA synthetase

23
Q

tRNA

A
  • carries specific amino acid

- CCA sequence at 3’ end which binds amino acids

24
Q

Wobble Hypothesis

A
  • proposed by Francis Crick

- anticodon of tRNAs can still bind successfully to codon whose 3rd position requires non-standard base pairing

25
Q

A site

A

-acceptor site

26
Q

P site

A

-peptidyl site, where peptide bond forms that adds amino acid to polypeptide chain

27
Q

E site

A

-exit site

28
Q

Translation (4 steps)

A
  1. aminoacyl tRNA diffuses into A site, anticodon binds to codon on MRA
  2. Peptide bond forms between amino acid on aminoacyl tRNA (A site) and growing polypeptide on tRNA (P site)
    3/4. Ribosome moves along 3 bases and all 3 tRNAs move down one position
  3. New aminoacyl tRNA moves in A site
29
Q

What initiates translation?

A

-tRNA loaded with Met

30
Q

What terminates translation?

A
  • presence of one STOP codon, not recognizes by tRNA

- STOP codon binds to release factor which alters catalytic activity

31
Q

Polyribosomes/Polysomes

A
  • many ribosomes attach to one strand of mRNA

- makes protein quicker

32
Q

Molecular Chaperones

A
  • help proteins fold

- bind to ribosomes near ‘tunnel’ where the growing peptide exits

33
Q

Post-Translational Modifications (PTMs)

A
  • chemical modifications of protein structure
  • generally involve addition of functional groups/small molecules to protein
  • has major effect of charge, shape, & function

BIOLOGY 130 (11 decks)

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