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genetics > lecture 24 > Flashcards

lecture 24 Flashcards

transcription and intron processing

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Biology 101 flashcards
1
Q

what is the central dogma?

A

DNA(genotype) -> mRNA(intermediate) -> protein(phenotype)

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2
Q

where does transcription occur in eukaryotic cells?

A

nucleus

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3
Q

when does transcription occur?

A

in waves either at G1/S or G2/M

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4
Q

what is the DNA strand that mRNA is built from?

A

template strand

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5
Q

what is the exact same sequence of nucleotides in the mRNA except T, i.e., the DNA strand that is not being transcribed?

A

coding strand

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6
Q

what direction does transcription occur in?

A

5’ to 3’

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7
Q

what end are nucleotides added to?

A

3’ growing tip

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8
Q

what form must DNA be in for transcription to occur?

A

euchromatin

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9
Q

how does DNA become euchromatin from a heterochromatic state?

A

the histone cores are de-acetylated thereby reducing the positive charge of the core and loosening the wrapped DNA

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10
Q

what occurs during the recognition step of transcription?

A

a large complex of proteins form at the TATA box(promotor region) including TATA binding protein

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11
Q

what occurs during the initiation step of transcription?

A

other transcription factors bind to promotor region at TATA box and a mediator complex including ATPase and helicase unwind DNA, forming transcription bubble; unphosphorylated RNA Polymerase II binds to template strand via active site

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12
Q

what occurs during the elongation step of transcription?

A

RNA Polymerase II is phosphorylated at its carboxyl end by the mediator complex, allowing it to traverse the template strand and make an RNA copy; reads 3’ to 5’

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13
Q

what occurs during the termination stage of transcription?

A

two protein complexes(CPSF and CSTF) recognize poly A signal; strand is cleaved

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14
Q

what are the function of the 5’ guanine cap?

A
  • regulation of transport out of nucleus through pore
  • allows for translation as it helps the ribosome recognize the message
  • prevention of mRNA degradation in the cytoplasm
  • intron splicing
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15
Q

when is the 5’ guanine cap added?

A

once the RNA transcript is ~30 nucleotides long

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16
Q

where does ribonuclease cleave the nascent RNA?

A

downstream of the conserved AAUAAA site

17
Q

what are the functions of the 3’ poly A tail?

A
  • enhances stability of RNA molecule
  • regulates transport to the cytoplasm
18
Q

what is he mechanism by
which introns are removed?

A

splicing

19
Q

what is the protein/RNA complex that
directs and insures proper RNA splicing?

A

spliceosome

20
Q

what is hnRNA?

A

aka pre-mRNA, immature single-stranded mRNA that is present in the nucleus that contains introns

21
Q

what is snRNP?

A

small nuclear RNA molecules
associated with specific ribonuclear
proteins playing essential role in splicing

22
Q

what removes introns in tRNA genes?

A

proteins

23
Q

what type of intron catalyzes its own removal from mRNA, tRNA, and rRNA precursors using guanosine‐5’‐
triphosphate (GTP), or another nucleotide cofactor – Ribozymes?

A

self-splicing introns (group 1)

24
Q

how do group 2 self-splicing introns differ from group 1?

A

group 2 does not require GTP to remove themselves like group 1 does, instead group 2 requires the assistance of proteins

25
Q

what are the parts of an intron?

A
  • GU nucleotide sequence at the 5’ splice site (donor site)
  • AG nucleotide sequence at the 3’ splice site (acceptor site)
  • Polypyrimidine Tract (PPT) just upstream of the 3’ splice site that promotes the assembly of the spliceosome
  • ranch Point Sequence (UACUAAC) – binding site for snRNP‐U2
26
Q

what is a regulated process that results in a single gene coding for multiple proteins?

A

alternative splicing

27
Q

what type of factors involved in alternative splicing are usually proteins that control gene expression?

A

trans-acting factors

28
Q

what type of factors involved in alternative splicing DNA sequences in the vicinity of a gene
required for gene expression?

A

cis-acting factors

29
Q

where does transcription occur in plants?

A

mitochondria or chloroplasts

genetics (30 decks)

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