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Biology > Chapter 17 - Expression of Genes > Flashcards

Chapter 17 - Expression of Genes Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

functional RNA

A

tRNA, rRNA

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2
Q

central dogma

A

explanation of the flow of genetic material:
DNA => RNA => protein

transcription & translation

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3
Q

Beadle and Tatum’s experiment

A
  • bombarded red bread mold with X-rays
  • analyzed relationship between metabolic pathway of arginine biosynthesis and mutated genes

-explained the “one gene one enzyme” hypothesis

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4
Q

degeneracy/redundancy of codons

A

many-to-one structure-function relationship
e.g. more than one codons (synonymous codons) code for a particular amino acid

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5
Q

Sense strand

A

(non transcribing strand)
-DNA strand that is not used for mRNA transcription

  • directed in 5’-3’ direction
  • contains same sequence as mRNA (except T)
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6
Q

Antisense strand

A

(template strand)
-template used for transcription to make mRNA

-antisense because its direction is 3’-5’ as the mRNA needs to be transcribed in 5’-3’ direction

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7
Q

Start codon

A

AUG - methionine

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8
Q

Stop codon

A

UAA / UAG /UGA

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9
Q

Site of transcription

A

eukaryotes - in the nucleus
prokaryotes - in the cytoplasm (nucleoid region)

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10
Q

RNA polymerase (II)

A
  • enzyme for transcription
  • binds to promoter region on DNA
  • acts like helicase: unwinds DNA double helix
  • acts like DNA polymerase III: adds RNA nucleotides to 3’ OH end of transcript
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11
Q

Transcription factors

A

mediate binding of RNA polymerase

+

initiation of transcription

1) general TF - responsible for all transcriptions in every cell
2) specific TF - works specifically at specific time in a specific cell

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12
Q

Stages of transcription

A

1) Initiation
- formation of transcription initiation complex

a) RNA polymerase (II) on promotor
b) general, specific transcription factors
c) transcription unit - DNA region downstream of promotor

2) Elongation
- RNA polym II moves along template strand and adds complementary RNA nucleotides to 3’ OH end of transcript

3) Termination
a) in prokaryotes: terminator sequence transcribed, RNA polymerase detaches from DNA template
b) in eukaryotes: polyadenylation signal recognized by nuclease which cleave mRNA from RNA polymerase II

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13
Q

RNA processing in eukaryotes

A

1) 5’ capping
- adding modified guanine to 5’ end of pre-mRNA

2) 3’ poly A tail
- adding 50-250 adenine nucleotides to 3’ OH end of pre-mRNA

3) RNA splicing
last step of RNA processing

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14
Q

Intron

A

INTervening RegiON
-non-coding segments

  • removed during RNA splicing
  • increases probability of crossing over
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15
Q

Exon

A

Expressed regiON
-coding segments

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16
Q

5’ capping

A

method of RNA processing in eukaryotes
-adding modified guanine to 5’ end of pre-mRNA

-role: protect mRNA from nuclease, promote export of mRNA through nuclear pore

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17
Q

3’ poly A tail

A

method of RNA processing in eukaryotes
-adding 50-250 adenine nucleotides to 3’ OH end of pre-mRNA

-role: protect mRNA from nuclease, promote export of mRNA through nuclear pore

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18
Q

RNA splicing

A

last step of RNA processing in eukaryotes
(occurs in spliceosome - complex of protein & DNA)

  • ribozyme removes introns in pre-mRNA
  • keeps axons
19
Q

Alternative RNA splicing

A
  • 2+ final mRNA produced from single mRNA
  • depends on which segments are treated as exon/intron

-increase genetic diversity

20
Q

Large scale mutation

A

1) alteration in chromosome number
a) aneuploidy (2n+1, 2n-1)

b) polyploidy (3n, 4n etc.)

2) Alteration in structure of chromosome
a) deletion
b) duplication
c) inversion
d) translocation - fragments of one chromosome exchanged with non-homologous chromosome

21
Q

Small scale mutation

A 
point mutation (changes in one/few nucleotide pairs) 
1) nucleotide pair substitution (during DNA rep and DNA repair)

a) silent - no effect (change to synonymous codon)
b) missense - original codon changed to different codon, different amino acid formed
e.g. wild type beta- globin (glutamine) to sickle cell beta globin (valine)
c) nonsense - original codon changed to stop codon
(UAA, UAG, UGA), produced premature polypeptide

2) nucleotide pair insertion/deletion
- causes frameshift

22
Q

tRNA

A
  • functional RNA
  • contains anticodon
  • transfer amino acid from cytoplasmic pool to ribosome
  • clover shaped (2D), L shaped (3D)
  • approximately 20 different tRNAs

1) empty (uncharged) tRNA - no amino acid on 3’ end
2) charged (aminoacyl) tRNA - amino acid attached to 3’ end
3) peptide tRNA - many amino acids attached to 3’ end

23
Q

aminoacyl tRNA synthetase

A

covalently bonds tRNA with corresponding amino acid
-amino acid and uncharged tRNA enters active site

-forms aminoacyl (charged) tRNA

24
Q

ribosome for translation

A

-composed of rRNA and protein

a) large subunit
- EPA sites
b) small subunit

25
Q

Translation process

A

1) initiation
- forms translation initiation complex (mature mRNA, initiator tRNA (methionine), ribosome)

  • small ribosomal subunit binds to mRNA
  • large ribosomal subunit binds
  • hydrolysis of GTP provides energy for assembly
  • initiator tRNA bonds to start codon

2) elongation
a) codon recognition
b) peptide bond formation between amino acids
c) translocation of ribosome

3) termination
- occurs when stop codon (UAA, UAG, UGA) reaches A site of ribosome
- releasing factor binds to A site and promotes hydrolysis of initiation complex

26
Q

Role of GTP during translation

A

hydrolysis of GTP provides energy for assembly of initiation complex

(mature mRNA, initiator tRNA (methionine), ribosome)

27
Q

polyribosome

A

simultaneous translation - where several ribosome are attached to single mRNA

28
Q

When does gene expression occur?

A

Usually in the G1 and G2 phase of the cell cycle

29
Q

Triplet code

A

four nucleotides (ATGC) 4^3 =64 possible codes to code for amino acids

30
Q

Where does translation occur?

A

In both bound and free ribosomes

31
Q

Central dogma location

A

Transcription - nucleus
RNA processing - nucleus
Translation - ribosome (free and bound) in cytoplasm

32
Q

Exceptions to universality of codon table

A

Mitochondrial and chloroplast DNA - use their own codon table
-explained by endosymbiotic theory

33
Q

Wobble theory

A

61 (64 - 3 stop codons) make 20 different amino acids

  • explained by redundancy of genetic codon
  • flexible base pairing for 3rd codon of mRNA
34
Q

enzyme required for transcription

A

RNA polymerase (II)

35
Q

TATA box

A

Part of promoter, initiates transcription

36
Q

Transcription factors

A

-help the binding of RNA polymerase II to promoter

1) General transcription factor
- responsible for all transcriptions in all cells
2) Specific transcription factor
- works specifically at specific time and in specific cell

37
Q

tRNA shape

A

2D - clover shaped
3D - L-shaped

38
Q

Aneuploidy

A

Abnormal number of particular chromosome (2n+1, 2n-1)

39
Q

Polyploidy

A

Abnormal extra set of chromosome

(3n, 6n)

40
Q

Alteration in structure of chromosome

A

1) deletion - removal of fragment
2) duplication - segments existing more than once on same chromosome
3) inversion
4) translocation - exchange of fragments

41
Q

Point mutation

A

1) nucleotide pair substitution
- replacement of one nucleotide and its partner with another pair of nucleotides
- during DNA replication and DNA repair
a) silent mutation - change codon to synonymous codon
b) missense mutation - change codon to different codon
c) nonsense mutation - change to stop codons

2) nucleotide pair insertion/deletion
- alteration of reading frame

42
Q

silent mutation

A

type of nucleotide pair substitution (point mutation)

  • change of codon to synonymous codon
  • due to wobble theory, no changes in phenotype
43
Q

missense mutation

A

type of nucleotide pair substitution (point mutation)

  • change codon to different codon
  • formation of different amino acid
    e. g. sickle cell anemia (change glutamine to valine)
44
Q

nonsense mutation

A

type of nucleotide pair substitution (point mutation)

  • change codon to stop codon
  • production of premature polypeptide

Biology (25 decks)

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