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Biology 107 - Intro to Cell Biology > Lecture 12 - Gene Expression > Flashcards

Lecture 12 - Gene Expression Flashcards

1
Q

Where is DNA stored in eukaryotes?

A

nucleus

- flow into the cell is undirectional

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2
Q

What is a gene?

A
  • a region of DNA that directs the synthesis of an RNA molecule
  • unit of heredity
  • encode for proteins
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3
Q

What is a promoter?

A
  • a DNA sequence that directs/regulates transcription
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4
Q

What is transcription (DNA-RNA)?

A
  • encoding DNA to RNA
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5
Q

What is a template?

A
  • strand of DNA that is used in transcription
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6
Q

What direction is RNA made?

A
  • made 5’ - 3’

- antiparallel and complementary to the template

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7
Q

What is the coding strand?

A
  • complementary and antiparallel to the template

- not used in transcription

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8
Q

What is the transcript?

A
  • RNA product of transcription
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9
Q

What does RNA polymerase do?

A
  • catalyzes phosphodiester bonds between RNA nucleotides
  • RNA pol synthesizes 5’ - 3’
  • does not require a primer
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10
Q

Where do transcription and translation occur in eukaryotes?

A 
transcription = nucleus 
translation = cytoplasm
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11
Q

What are the three modifications in the nucleus?

A
  1. addition of a methyl-guanosine cap at the 5’ end
  2. addition of 100-200 adenosines to the 3’ end, poly-A tail
  3. RNA splicing (removal of introns)
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12
Q

What is translation?

A
  • process in which the genetic code carried by a mRNA directs the synthesis of proteins from amino acids
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13
Q

What is the genetic code?

A
  • 3 nucleotides = one amino acid
  • 3 “letter” word = codon
  • universal
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14
Q

What was the Nirenberg Experiment?

A
  • synthesized an artificial mRNA with repeating UUU codons using translation
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15
Q

What is the codon table?

A
  • 64 possible codons
  • 61 encode amino acids
  • 3 are non-associated
  • start codon (AUG)
  • stop codons (UAA, UGA, UAG)
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16
Q

What is tRNA?

A

transfer RNA

  • has a.a binding region and mRNA base-pairing region
  • not translated but functions in translation
17
Q

What is Aminoacyl tRNA synthetase?

A

-pairs correct a.a based on anticodon sequence (covalently link a.a to tRNA in the sequence-dependent matter)

18
Q

What are ribosomes?

A
  • catalyze peptide bonds
  • consists of three important sites (A,P,E)
  • proteins are synthesized from N-C by reading mRNA 5’-3’
19
Q

What are the large and small subunits of ribosomes?

A
  • large = contains rRNA and is catalytic

- small = contains rRNA and is recognition

20
Q

What are the steps in translation?

A
  • initiation
  • elongation
  • termination
21
Q

What happens in the initiation phase?

A
  • ribosomal binding site positions the small subunit such that AUG sits in the P site
  • mRNA associates with ribosome vis base pairing with mRNA and rRNA = specificity
22
Q

What happens in the elongation phase?

A
  • bind = tRNA a.a approaches A site and binds to the mRNA
  • bond = peptide bond forms between #1 tRNA and #2tRNA and the growing chain moves to tRNA in A site
  • shift = ribosome shifts down mRNA (to 3’ end) in a one codon step
23
Q

What happens in the termination phase?

A
  • STOP codons
  • when the ribosome encounters a stop codon in A site the ribosome stalls unless a release factor enters
  • ribosome components dismantle and are recycled
24
Q

What transcription and translation coupling?

A
  • prokaryote only

- translation occurs at the same place, therefore can occur at the same time

25
Q

What are mutations?

A
  • heritable changes in base sequences that modify the information content of DNA
26
Q

What are substitutions?

A
  • base-pair substitutions in the replacement of one nucleotide and its partner with another pair
27
Q

What are silent mutations?

A
  • because of redundancy in the genetic code

- no change in the primary sequence

28
Q

What are missense mutations?

A
  • encode wrong amino acid
  • change in the primary sequence
  • may affect protein function
29
Q

What are nonsense mutations?

A
  • premature stop codon
  • shortened protein
  • may affect protein function
30
Q

What are frameshift mutations?

A
  • single bp addition or deletion that changes the reading frame of a protein
31
Q

What is the difference between spontaneous and induced mutations?

A
  • spontaneous = errors in DNA replication

- induced = caused by mutagens

Biology 107 - Intro to Cell Biology (12 decks)

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