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Genetics > Chapter 12 > Flashcards

Chapter 12 Flashcards

1
Q

Transcription definition

A

The copying of DNA sequence into RNA sequence

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2
Q

Protein-encoding genes (structural genes)

A

encode aa sequence of polypeptide

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3
Q

messenger RNA (mRNA)

A

made by transcription of protein-coding gene, mRNA base sequence determines aa sequence of polypeptide during translation

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4
Q

Translation definition

A

produces polypeptide using info in mRNA

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5
Q

DNA replication

A

makes DNA copies that are transmitted from cell to cell and parent to offspring

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6
Q

Gene expression

A

overall process by which info within gene is used to produce functional product which can determine trait (with help of environment)

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7
Q

Regulatory sequences

A

site for binding of regulatory proteins, influences the rate of transcription (usually found upstream)

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8
Q

Promoter

A

site for RNA polymerase binding, signals beginning of transcription

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9
Q

Terminator

A

signals end of transcription

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10
Q

Ribosome-binding site

A

site for ribosome binding to mRNA in bacteria (translation begins near this site in mRNA

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11
Q

In eukaryotes, the ribosome binds to the _________ in the mRNA, and the ribosome scans the RNA for a ______ codon.

A

7-methylguanosine cap, start

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12
Q

What is the start codon in eukaryotes vs. bacteria?

A

Eukaryotes —> methionine
Bacteria —-> formylmethionine

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13
Q

Polycistronic

A

bacterial mRNA that encodes for two or more polypeptides

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14
Q

Template strand

A

DNA strand that’s actually used as a template/guide to be transcribed into mRNA

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15
Q

Coding strand/sense strand/nontemplate strand

A

Strand opposite to the coding strand (identical to base sequence in mRNA made from template strand)

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16
Q

Transcription factors

A

recognize promoter and regulatory sequences to control transcription

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17
Q

3 stages of transcription

A

initiation (start), elongation (grow), termination (stop)

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18
Q

Initiation

A

Promoter is recognition site for transcription factors, which enable RNA polymerase to bind to promoter. DNA is then denatured into bubble known as open complex.

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19
Q

Elongation/synthesis of RNA transcript

A

RNA polymerase slides along DNA in open complex to synthesize RNA

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20
Q

Where do promoters vary?

A

at -35 and -10 sequences

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21
Q

Most common sequence in promoter

A

consensus sequence - likely to result in high level of transcription, sequences that deviate from consensus sequence typically result in lower levels of transcription

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22
Q

What’s in the RNA polymerase holoenzyme? What’s it do?

A

Core enzyme (five subunits) and sigma factor (one subunit). Holoenzyme binds to DNA, scans along until it encounters promotor. When it does, sigma factor recognizes -35 and -10 sequences.

23
Q

Helix-turn-helix structure in sigma factor

A

involved in tighter binding to DNA

24
Q

Closed complex

A

binding of RNA polymerase to promoter

25
Q

Open complex

A

formed when TATAAT box in the -10 sequence is unwound, a short RNA strand is made within open complex (sigma factor released at this point, marking end of initiation)

26
Q

RNA polymerase directionality

A

RNA polymerase slides along template strand in 3’ to 5’ direction, RNA synthesized in 5’ to 3’ direction using nucleoside triphosphates (NTPs) as precursors

27
Q

Location of _____ determines template strand and therefore direction of transcription.

A

promoter

28
Q

2 different mechanisms of termination in E. coli

A

rho-dependent and rho-independent (facilitated by uracil-rich sequence at 3’ of RNA and stem-loop upstream) (both mechanisms have hairpin structure)

29
Q

3 different RNA polymerases that transcribe Nuclear DNA

A

RNA pol I - transcribes all rRNA genes (except 5S rRNA)
RNA pol II - transcribes all protein-encoding genes (synthesizes mRNAs) and some snRNA genes for splicing
RNA pol III - transcribes all tRNA genes, 5S rRNA gene, microRNA genes

30
Q

Conserved sequences

A

usually upregulated, an example is the TATA box

31
Q

Basal transcription

A

basal=general, baseline amount of transcription factors needed for RNA pol to function

32
Q

Regulatory elements (name 2 types)

A

short DNA sequences that affect binding of RNA pol to core promoter
1. Enhancers - stimulate transcription
2. Silencers - inhibit transcription

33
Q

cis-acting elements that regulate gene transcription

A

DNA sequences that exert their effect only over particular gene (ex: TATA box, enhancers, silencers)

34
Q

trans-acting factors that regulate gene transcription

A

regulatory proteins that bind to such DNA sequences

35
Q

3 categories of proteins required for basal transcription to occur at promoter

A

RNA pol II, 5 different proteins called general transcription factors (GTFs), protein complex called mediator

36
Q

2 models of termination

A

Allosteric model - “do nothing” model, RNA pol II destabilized & dissociates from DNA
Torpedo model - exonuclease binds to 5’ end of RNA and degrades it in 5’ to 3’ direction, catches up to pol and causes termination

37
Q

Colinearity of gene expression

A

sequence of DNA in the coding strand corresponds to the sequence of nucleotides in the mRNA

38
Q

Does RNA modification occur in eukaryotes or prokaryotes?

A

eukaryotes

39
Q

Exons vs. introns

A

exons = coding sequences, introns don’t code for anything and are spliced out

40
Q

4 ways to modify RNA

A
  1. Splicing
  2. Processing of rRNA and tRNA transcripts to smaller functional pieces
  3. 5’ Capping
  4. 3’ polyA tailing of mRNA transcripts
41
Q

RNA processing

A

larger RNA transcripts cleaved into smaller functional pieces (ex: rRNAs and tRNAs)

42
Q

RNA processing - transfer RNAs

A

also made as large precursors, cleaved at both 5’ and 3’ ends to produce mature, functional tRNAs

43
Q

RNaseP

A

an endonuclease, also a ribozyme (catalyst composed of RNA)

44
Q

3 splicing mechanisms (all 3 involve removal of intron RNA and covalent linkage of exon RNA fragments)

A

Group I intron splicing (self-splicing)
Group II intron splicing (self-splicing)
Spliceosome (pre-mRNA)
(slide 52 chart)

45
Q

Self-splicing

A

can occur in vitro w/out proteins, not aided with additional enzyme, instead the RNA itself functions as its own ribozyme

46
Q

Maturases

A

protein that enhances rate of splicing

47
Q

What is the spliceosome made of?

A

several subunits called snRNPs (small nuclear RNA and a set of proteins = combo of active RNA and proteins, displays active RNA), pulls back pieces we don’t need & they dip somehow

48
Q

Functions of spliceosome subunits

A

bind to intron sequence and recognize intron-exon boundaries, hold pre-mRNA in correct configuration, catalyze rxns that remove introns and covalently link exons (occurs via metalloribozyme)

49
Q

Alternative splicing

A

pre-mRNA with multiple introns can be spliced in different ways, two or more polypeptides can be derived from a single gene

50
Q

Constitutive vs. alternative exons

A

constitutive - always exons
alternative - sometimes bits of info (sometimes cut out like introns if not used)

51
Q

Uses of 5’ cap (7-methyl-guanosine)

A

protect poly-A tail from degradation, protects from breakage while free floating, protect against enzymes,
important for exiting nucleus

52
Q

RNA editing

A

can occur by changing one type of base to another, modifying (not pulling old out and putting new in)

53
Q

Important table on slides ____

A

77 & 78

54
Q

FuG

A

gUh

Genetics (14 decks)

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