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Flashcards in Genetic Expression Deck (42)
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1

Define/Explain the steps of Central Dogma

Flow of information in the cell
DNA->*transcription*->mRNA->*translation*->protein

2

What is the promotor

DNA sequence that directs/regulates transciption
site of RNA polymerase
-35 to -10

3

What direction do you read the template strand

3' -> 5'

4

How many nucleotides form a protein

three

5

DNA is read (transcription occurs) in the _' to _' end

3' to 5' (making RNA 5' to 3')

6

What direction does the template run away from the promotor

3' to 5'

7

Transcription changes _____ into ______

DNA into RNA

8

What is RNA polymerase

Enzyme of transcription
-binds double stranded DNA at promotor
-unwinds double helix, create transcription bubble
-initiate transcription at +1
-aligns first two ribonucleotides (5' end of new mRNA)

9

How is the template strand chosen

Based on direction of promotor

10

What happens at termination of transcription

RNA sequence that signal the end (terminators), RNA polymerase dissociates (falls off)

11

Where does transcription happen, where does translation happen (in eukaryotes)

transcription: in nucleus
translation: in cytoplasm

12

Post-transcriptional processing only happens in _________ because ________________________.

1. eukaryotes
2. transcription occurs in the nucleus, translation occurs in cytoplasm (time btw end of transcription and start of translation)

13

What modifications occur in post-transcriptional processing? Why?

1. Addition of methyl guanosine cap at 5' end: "hides" the 5' end from exonuclease digestion
2. Addition of 100-200 adenosines to 3' end (poly-A tail): prevent and delay exonuclease digestion, aids in translation initiation

14

What is RNA splicing

removal of introns

15

What are introns and exons

Introns (remove): non amino acid coding regions (intervening sequences) found on genes DNA but not mature RNA
Exons (leave): amino acid coding regions

16

What is the spliceosome

Enzyme, complex of snRNPs, recognize sequence at intron/exon boundaries

17

Steps of RNA splicing

1) SnRNPs bind intron/exon boundaries and loop out the intron
2) intron cut out by cutting at 5' end of intron
3) excised intron in lariat shape (created by 5'-2' linkage of RNA)
4) exons ligated together

18

Why splice?

remove interrupting sequences, alternative splicing (mix and match of exons makes similar but not identical proteins from same gene. Ex. neuron vs muscular protein)

19

Translation changes _____ into ______.

RNA into protein

20

What signals start and stop of translation

start and stop codons

21

mRNA vs tRNA

mRNA: codon
tRNA: anticodon (antiparallel and complementary to mRNA)

22

Function of tRNA

carry appropriate amino acid to ribosome

23

Function of Aminoacyl tRNA synthetases

"the translator"
pairs correct amino acid based on anticodon sequence, covalently links amino acid to tRNA in sequence dependent manner

24

proteins are synthesized in what direction

N->C by reading mRNA 5'->3'

25

Large vs small ribosomal subunits in prokaryote vs eukaryotes

Prokaryotes: 70s=30s(small)+50s(large)
Eukaryotes: 80s=40s(small)+60s(large)

26

The large ribosomal subunit contains _____ and its function is ______. The small ribosomal subunit contains _______ and is involved in _________________.

rRNA, catalytic, rRNA, recognition of mRNA

27

The three sites of the large subunit

A:approach
P:polymerization
E:exit

28

What is the ribosomal binding site

small ribosomal subunit in prokaryotes, sequence in mRNA that is recognized by base pairing with rRNA

29

What are the three steps in translation (in prokaryotes)

Initiation, elongation, termination

30

Briefly explain initiation phase in translation

ribosomal binding site positions the small subunit such that AUG sits in P-site, the large subunit then associates such that F-met tRNA sits in P-site
"harmburger"