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Cell and Molec > Lecture 5 > Flashcards

Lecture 5 Flashcards

1
Q

Recall the CENTRAL DOGMA

A

DNA -> RNA (transcription) -> protein (translation)

ALL cells use this

In Eukaryotes:
-DNA undergoes transcription, pre-mRNA undergoes 5’ capping, RNA splicing, 3’ polyA tail in NUCLEUS; mRNA is exported out of nucleus, translated to protein outside nucleus

In Prokaryotes:
-DNA undergoes transcription - mRNA - translated to protein; NO nucleus

EVERY cell processes information like this

Information processing (how a cell goes from DNA to protein)

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2
Q

RNA processing

A

RNA splicing
5’ cap
3’ PolyA tail
ONLY in eukaryotes

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3
Q

Eukaryotes vs Prokaryotes

A

Eukaryotes are LARGER, possess introns/exons, RNA processing, and nucleus (prokaryotes don’t have those)

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4
Q

Product of a gene is NOT always turned into a protein

A

Cells can regulate how much is made into protein (usuallly at transcription)

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5
Q

A cell can express different genes at

A

Different rates

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6
Q

Gene expression

A

1st step is transcription

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7
Q

What determines where RNA polymerase starts transcribing DNA?

A

Transcription of a gene produces an RNA complementary to one strand of DNA

The promoter

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8
Q

Transcription proceeds in a 5’ to 3’ direction using a

A

3’ to 5’ template

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9
Q

Bacterial promoters and terminators have specific

A

Nucleotide sequences that are recognized by RNA polymerase

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10
Q

Transcription in Bacteria

A

starts on a sequecnce call the Promoter: It is NOT a continuous strand of bases, occurs in segments (UNLIKE replication origin)

Transcription starts at the +1 (this is where the first nucleotide is added

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11
Q

In eukaryotes, the promoter is NOT in

A

RNA

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12
Q

Signals in the nucleotide sequence of a gene tell bacterial RNA polymerase

A

Where to start and stop transcription

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13
Q

Sigma Factor

A

Transcription factor that helps the RNA polymerase (one of the main differences between prokaryotic and eukaryotic)

Recognizes the Promoter

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14
Q

Terminator

A

Where transcription stops

Ends up in molecule of RNA (promoter does NOT)

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15
Q

Eukaryotic promoters

A

Contain sequences that promote the bindings of the general transcription factors

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16
Q

TBP binds to the TATA box and bends

A

The DNA molecule

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17
Q

General transcription Factors

A

found in EVERY single cell and initiate transcription

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18
Q

Regulatory Transcription factors

A

Regulate transcription (activators, repressors)

Vary on cell type

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19
Q

Some genes are transcribed using one DNA strand as a template, and others are transcribed from

A

The other DNA strand

20
Q

How does RNA polymerase differ from DNA polymerase?

A

DNA is transcribed into RNA by the enzymes RNA POLYMERASE

-Helicase opens the helix in RNA, too; opens as it goes, closes behind it; NO primer for transcription of RNA

21
Q

How do RNA and DNA differ from each other?

A

The chemical structure of RNA differs slightly from that of DNA
-RNA uses ribose (has one more OH), DNA uses deoxyribose (one less OH)

RNA uses uracil (one less methyl)

DNA uses thymine (one more methyl)

uracil forms a base pair with adenine

22
Q

Messenger RNAs

A

mRNA

Code for proteins

NOT translated to proteins

23
Q

Ribosomal RNAs

A

rRNAs

Form the core of the ribosome’s structure and catalyze protein synthesis

24
Q

MicroRNAs

A

miRNAs

Regulate gene expression by associated with RISC complex then binding to certain mRNA that it carries a message for and destroys that mRNA

25
Q

TransferRNAs

A

tRNAs

Serve as adaptors between mRNA and amino acids during protein synthesis

26
Q

Other noncoding RNAs

A

Used in RNA splicing, gene regulation, telomere maintenance, and many other processes

27
Q

RNA can fold into structures that are held together by

A

H bonds

28
Q

How does transcription Proceed?

A

TO begin transcription, eukaryotic RNA polymerase II requires a set of general transcription factors:

  • TATA and TFIID recognize promoter
  • Recruit TFIIB
  • TFIIB binds, recruits TFIIE and TFIIH and RNA polymerase II
  • TFIIH breaks H-bonds and acts as a helicase (does NOT stay the whole time like helicase does in DNA)
  • DNA melts, transcription factors dissociate
29
Q

RNA polymerase I

A

most rRNA genes

30
Q

RNA polymerase II

A

All protein-coding genes, miRNA, plus genes for other noncoding RNAs (e.g. those of teh spliceosomes)

31
Q

RNA polymerase III

A

tRNA genes, 5S rRNA gene, genes for many other small RNAs

32
Q

Eukaryotic vs. Prokaryotic Initiation

A

Eukaryotic
-TATA, TBP, TFIID recognize promoter, recruit TFIIB, binds to promoter, recruits TFIIE, TFIIH, polymerase II, TFIIH unwinds helix (closes right behind), DNA melts, transcription factors dissacoiate

Prokaryotic:
-Sigma factor binds to RNA polymerase, RNA polymerase binds to promoter at start site, begins RNA synthesis, sigma factor is released, polymerase calmps firmly on DNA, RNA synthesis terminated at stop site, polymerase and completed RNA released

33
Q

Phosphorylation of the tail of RNA polymerase II allows RNA-processing proteins to

A

Assemble

34
Q

TFIIH functions

A

1) Helicase

2) Phosphorylation
- Melt DNA, open up, phosphorylate

Phosphorylation acts as a docking site

ONLY RNA polymerase II does this (other proteins not made by RNA polymerase II do NOT have a cap)

35
Q

Eukaryotic mRNA molecules are modified by capping and polyadenylation

A

Capping: Occurs on 5’ ends, message is capped BEFORE trancription is even done

Tail: Poly-A tail is added at the EN of transcription (after message is completed)

36
Q

Major function of PolyA tail and 5’ cap

A

1) Stabilizes message/prevents being eaten by nucleases

2) Translate; helps DNA to realize that these are processed and don’t need to be destroyed

37
Q

There is ALWAYS s string of sequences at BOTH ends that are

A

NOncoding (start codon is NEVER right at the end)

38
Q

Special nucleotide sequences in a premRNA transcript signal the beginning and the end of an intron

A

pre-mRNA hasn’t been fully processed

There are very soncerved sequences that tell us where these sections are

Start codon is NEVER at the end, always separated by UTR

39
Q

An intron in a pre-mRNA molecule forms a branched structure during RNA splicing

A

Red “A” 100% conserved base; any mutations are fatal

3’ ydroxyl group attacks 5’ end

Lariat (bundle of introns that results from 3’ hydroxyl attacking 5’ end) will be degraded so you can reuse the bases

40
Q

Splicing is carried out by a collection of RNA-protein complexes called

A

snRNPs

RNA portion of snRNP base-pairs with sequences that signal splicing

It is the RNA that recognizes sequences in the introns

Active site created by two things (U2 and U6)

Excised intron in the form of a lariat

Exon junction complex

41
Q

Small nuclear ribonucleic proteins:

A

RNA protein complexes

42
Q

Spliceosome

A

One of largest complexes in cell

Binds at ends to bring together

43
Q

Some pre-mRNAs undergo alternative splicing to produce different mRNAs and proteins from the same

A

Gene

We can alternatively splice messages (splice 2 out, get completely different protein)

90% of proteins are alternatively spliced

Mix and match

44
Q

Most protein-coding human genes are broken into multiple

A

Exons and introns

Prokaryotes do NOT have introns and exons

Drosophila gene: 38000 different genes (record for alternative splicing)

45
Q

Eukaryotic and bacterial genes are organized

A

Differently

46
Q

A specialized set of RNA binding proteins signals that a complete mRNA is ready for export to the

A

Cytosol

Ribosomes are out in the cytoplasm

Will bind to proteins (proteins tell the cell message hass been processed)

Transport through nuclear pore => protein exchange (switch out for translation initiation factors)

47
Q

When a message is processed, it associates with a bunch of proteins that tell the cell if the information has been processed

A

Transported through nuclear pore

Protein exchange in nuclear pore

Cell and Molec (9 decks)

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