lecture 20 Flashcards by Jillian Kucey

how might someone know that it was a pre mRNA vs a mature mRNA

pre mRNA still has introns

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what is a lariat

the intron loop that got created through splicing

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what happens to a lariat

it gets degraded in the nucleus

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what end of mRNA interacts with start of next exon

free 3’ -OH end

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what carries out splicing

spliceosomes

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what are spliceosomes

snRNAs and ribonucleoproteins (snRNPs)

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which spliceosomes recognize the intron sequences on either end ?

U1 and U2

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what spliceosome binds to the same sequence as U1, making sure that U1 was correct?

U6 replaces it

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what spliceosomes create the active site to splice introns

U2 and U6

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what joins the 2 exons together and signals that no more work is needed by spliceosomes

exon junction complex

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what does lots of random chromatin signal about a cell

that its a non dividing cell

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what is the inner surface of the nuclear envelope lined by

nuclear lamina

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what is the nuclear lamina composed of

laminin

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what is laminin

intermediate filaments

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what is the nuclear pore complex composed of

~30 proteins called nucleoporins

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is the nuclear pore complex static

nope - replaced often

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what is a nuclear localization signal

a small protein with a positively charged amino acid sequence on it that acts as a tag to show it should be let IN to the nucleus

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whats the direction of an importin

cytoplasm -> nucleus

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whats the direction of an exportin

nucleus -> cytoplasm

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what are the 4 translational controls

initiation of translation
cytoplasmic localization of mRNA
mRNA stability
Regulatory RNAs

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what is initiation of translation mediated by

protein intercations with untranslated regions of mRNA

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what the most studied example of initiation of translation

Ferritin stores iron in cells.
if there’s low iron, we dont need to make anything, so Iron regulatory protein binds to region. if there’s high iron, iron inhibits the binding

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what can block the ribosome binding site in mRNA to repress translation? what translational control is that from?

translation repressor protein

initiation of translation

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what establishes anterior-posterior axis

mRNA localization

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what is cytoplasmic localization of mRNA

dispersed and separated mRNA to select which genes are transcribed/translated

what does biscoid mRNA on a fruit fly determine

anterior (head/thorax)

why is actin mRNA localized to leading edge of cell

for locomotion

what is mRNA stability impacted by (3)

with the 3' end poly A tail: length (gets shorter the longer its in cytoplasm) AU regions make it less stable protein interactions with the tail

what do miRNA do

degrade or repress mRNA to regulate gene expression and only produce the proper protein for that region

if the complimentary target mRNA is an extensive match to the RISC complex, what happens

the mRNA is rapidly degraded by nucleases within RISC complex

if it is a less extensive match of target mRNA for the RISC complex, then what happens

it gets knocked out to the cytosol where it is then degraded by nucleases in the cytosol (the risk protein isn't sure so it doesn't want to do it)

what makes up the RISC complex ? what does it create

RISC proteins double stranded RNA intermediate creates a single stranded miRNA

what does RISC stand for

RNA-induced silencing complex

what type of RNA plays a key role in development

miRNA

what cleaves double stranded foreign DNA

Dicer

what do siRNA do

involved In a silencing pathway to degrade foreign DNA

what is RNA interference (RNAi)

process that silences gene expression by degrading mRNA or blocking its translation

what does RNA interference target

complimentary RNA to siRNA

what happens to complimentary foreign RNA

it gets degraded

what complex is involved in transcriptional silencing

RITS complex

where is transcriptional silencing found

plants, animals, fungi

how does transcriptional silencing work

it does heterochromatin formation to reduce transcription

what is the single type of 4. post translational control

protein stability

what do we believe protein stability to be

we believe that it may be determined by the amino acids on the N terminus

where does degredation of proteins occur

within hollow cylindrical proteosomes

what do proteosomes recognize on proteins

if they are linked to ubiquitin

what transfers ubiquitin to proteins to be degraded

ubiquitin ligases

what happens to proteins after they've been degraded

released back into the cytosol

define cell division

process by which new cells arise from other living cells

what are the two types of cell cycles in eukaryotes

mitosis meiosis

what does mitosis generate

two identical daughter cells to the parent

what does meiosis generate

cells with half the genetic code of the parents

what is meiosis also known as

its the basis for producing new sexually reproducing organisms

whats the majority of the cell cycle

interphase

what are the 3 phases of interphase

G1, S, G2

where does synthesis happen in interphase

S phase

what are the 2 phases of the M phase

mitosis cytokinesis

what is cytokinesis

cell division

what is G0

resting phase/preparing phase (a part of G1)

what triggers the onset of G1

external signals

what is G1 phase

end of mitosis -> DNA replication

what is the S phase

synthesis phase Dna replication

what is the G2 phase

end of S phase -> beginning of mitosis

5 stages of mitosis

prophase prometaphase metaphase anaphase telophase

what are the 4 major checkpoints in cell cycle

G1 checkpoint S checkpoint G2 checkpoint M checkpoint

if conditions are not favourable at G1 checkpoint, what happens

it goes back to G0

why is G1 checkpoint a restriction point in mammalian cells

because once its past there, the cell is committed to cell division

what is the S checkpoint

checks for DNA damage during replication

how many checkpoints does interphase have

what is the G2 checkpoint

entry into mitosis checks for DNA damage and ensures duplication

where is the M checkpoint

at the entry to anaphase

what does the M checkpoint do

ensures chromosomes aligned and attached to spindle

are cyclin dependent protein kinases (Cdks) levels the same throughout the cell cycle

yes

whats used to regulate Cdks

cyclin

do cyclin levels remain the same through cell cycle

what does Cdk regulatory protein dip

activate kinase activity

is cyclin and Cdk pairing specific

yes

without cyclin there would be no _______

activity

how many Cdk proteins are in budding yeast ? what is it called

there is 1 called Cdk1

what are the 2 checkpoints in budding yeast

START (between G1 and S) G2-M transition

how many Cdks in eukaryotes

many (doesn't specify)

what are the 3 cyclins in eukaryotes

G1/S cyclin S cyclin M cyclin