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Genes: Organisation and Function > Lecture 13 > Flashcards

Lecture 13 Flashcards

1
Q

Eukaryotes:

A
  • very varied, include fungi, insects, alga, protozoan, flowers, animals
  • multicellular, different sets of expressed genes depending on the cell type
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2
Q

Prokaryotic cell:

A
  • Cell membrane, cell wall, flagellum, ribosomes, DNA in a nucleoide structure
  • Genes expressed according to the signals recieved
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3
Q

Eukaryotic cell:

A
  • Larger size than prokaryotic cell
  • Their DNA is located in a nuclear envelope within a Nucleus. They have a lot more DNA.
  • A nucleolus is where the ribosomes are created
  • Gene regulation is easy due to selection of transcription factors and entry to the nucleus
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4
Q

Chromosomes in the nucleus of eukaryotic cells:

A
  • Metaphase chromosomes are highly structured, as genes aren’t being transcribed
  • Interphase chromosomes are slightly less structured
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5
Q

DNA packaging in eukaryotes:

A
  • Chromatin packages DNA into histone proteins (DNA double helix, chromatin, nucleosomes, condensed section of chromatin)
  • This is dynamic as DNA moves in response to the cell cycles and in response to what genes are being turned on and off in the nucleus.
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6
Q

Nuclear localisation:

A
  • A region of non-transcribed genes is found around the outside of the nucleus. Genes found here are usually silenced
  • Genes that are transcribed are at the centre of the nucleus.
  • This happens in response to signals from the external environment
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7
Q

Factors influencing genome size:

A
  • Gene density (intergenic regions)
  • Introns (size and number)
  • Repeats
  • Gene size between eu- and pro- karyotes are pretty similar, but the genome size varies due to each gene having their own regulating sequences.
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8
Q

Eukaryotic RNA polymerases:

A
  • 3 DNA dependent RNA polymerases
  • ## beta and beta’, alpha, and additional enzyme specific subunits.
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9
Q

RNAPI:

A
  • Ribosomal RNAs
  • 5.8s
  • 18s
  • 28srRNA genes
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10
Q

RNAPII:

A
  • all protein coding genes, plus snoRNA genes, miRNA genes, siRNA enes, and most snRNA genes
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11
Q

RNAPIII:

A
  • tRNA genes, 5S rRNA gnes, some snRNA genes and genes for other small RNAs
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12
Q

Eukaryotic RNAs:

A
  • Lots of types!
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13
Q

mRNA:

A
  • messenger RNA

- code for proteins

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14
Q

rRNA:

A
  • Ribosomal RNA

- Form the basic structure of the ribosome and catalyse protein synthesis

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15
Q

tRNA:

A
  • Transfer RNAs

- Central to protein synthesis as adaptors between mRNA and amino acids

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16
Q

snRNAs:

A
  • Small nuclear RNAs

- Function in a variety of nuclear processes, including the splicing of pre-mRNA

17
Q

snoRNAs:

A
  • Small nucloelar RNAs

- Used to process and chemically modify rRNAs

18
Q

scaRNAs:

A
  • Small cajal RNAs

- Used to modify snoRNAs and snRNAs

19
Q

miRNAs:

A

Micro RNAs

- Regulate gene expression typically by blocking translation of selective mRNAs

20
Q

siRNAs:

A
  • Small interfering RNAs
  • Turn off gene expression by directing degradation of selective mRNAs and the establishment of compact chromatin structures
21
Q

3’ modifications:

A
  • Run of Adenines As
  • Important for stability and regulation of translation
  • Ribosomal endonucleases can’t degrade it
22
Q

5’ cap:

A
  • Protects from degradation

- Involved in when the RNA is expressed/translated

23
Q

Gene organisation in the Drosophila Adh region:

A
  • osp (outspread wings) mutations mapped to both sides of the Adh genes, as it is within an intron of the Adh gene
  • Adh, Adhr, two other genes within introns of osp!
  • Multiple start sites, multiple poly(A) sites and different splicing
24
Q

Initiation of transcription:

A
  • RNAPII is involved in protein coding genes
  • Steps in transcription at Class II (RNAPII) promoters:
    1. Formation of the pre-initiation complex
    2. Separation of the 2 DNA strands
    3. Initiation
    4. Promoter clearance
    5. Elongation
    6. Termination
25
Q

Transcription complexes involve these things:

A
  • Transcription initiation (RNAP starts)
  • Transcription termination (RNAP falls off)
  • 5-methyl guanine cap
  • PolyA tail at 5’ end
26
Q

A TATA box is:

A
  • A consensus sequence found in genes that codes for the promoter
  • The RNAP recognises the TATA box
  • A sigma factor or GTF recognises the promoter allowing RNAP to bind and transcribe
27
Q

Transcription Factor TFIID:

A
  • TATA binding protein
  • TBP associated factors
  • Binds core promoter elements and initiates assembly of the pre-initiation complex on the promoter
  • Different TFs recognise different sequences so different genes are transcribed by RNAP
28
Q

Phosphorylation steps on the 3’ tail after transcription:

A
  • Determine capping, intron splicing, polyadenylation and intron splicing
  • Important for what happens next for that particular transcript

Genes: Organisation and Function (33 decks)

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