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MCAT Biochem > Transcription > Flashcards

Flashcards in Transcription Deck (23)
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1

Helicase and topoisomerase:

unwind the DNA double helix

2

RNA polymerase 2

binds to the TATA box within the promoter region of the gene (25 base pairs upstream from first transcribed base)

3

hnRNA

synthesized from the DNA template (antisense) strand

4

Posttranscritional modifications include:

- a 7 - methylguanylate triphosphate cap is aded to the 5' end
- a polyadenosyl (PolyA) tail is added to the 3' end

5

Splicing

is done by snRNA and snRNPs in the spliceosome; introns are removed in a lariat structure, and eons are ligated together

6

Prokaryotic cells can increase WHAT?

the variability of gene products from one transcript through POLYCISTRONIC GENES (starting transcription in different sites within the gene leads to different gene products)

7

Eukaryotic cells can increase WHAT?

the variability of gene products through alternative splicing (combining different eons in a modular fashion to acquire different gene products)

8

generating a protein is done where?

in the cytoplasm

9

transcription

the creation of mRNA from a DNA template

10

RNA polymerase I

located in the nucleus and synthesizes rRNA

11

RNA polymerase II

located in the nucleus and synthesizes horn (preprocessed mRNA) and some small nuclear RNA (snRNA)

12

RNA polymerase III

located in the nucleus and synthesizes tRNA and some rRNA

13

In what direction does the RNA polymerase travel?

3' --> 5'

14

RNA polymerase

does not proofread its work

15

coding strand (sense strand)

not used as a template during transcription
complementary to the template strand

16

Where does the RNA polymerase II bind?

the TATA box

17

heterogenous nuclear RNA (hnRNA)

The primary transcript that is formed when the DNA double helix reforms.
mRNA is derived from horn via post transcriptional modifications

18

Maturation of the horn includes:

splicing of the transcript to remove noncoding sequences (introns) and ligate coding sequences (exons) together

19

Splicing is accomplished by the

spliceosome

20

In the spliceosome,

small nuclear RNA (snRNA) molecules couple with proteins known as small nuclear ribonucleoprotines (snRNPS or "snurps"). The snRNP/snRNA complex recognizes both he 5' and 3' splice sits of the introns. These noncoding sequences are excised in the form of a lariat (lasso - shaped structure) and then degraded

21

7 - methylguanylate triphosphate cap

this is added at the 5' end of the hnRNA molecule.
This cap is added during the process of transcription and is recognized by the ribosome as the binding site. It also protects the mRNA from degradation in the cytoplasm

22

3' Poly - A Tail

A poly A tail is added to the 3' end of the mRNA transcript and protects the message against rapid degradation.

23

alternative splicing

occurs in eukaryotic cells
the primary transcript of hnRNA may be spliced together in different ways to produce multiple variants of proteins encoded by the same original gene.

the function in the regulation of gene expression, in addition to generating protein diversity.