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Clinically Based Concepts II > transcription > Flashcards

transcription Flashcards

1
Q

define transcription

A

process that makes RNA from DNA

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2
Q

why is the process of transcription called it?

A

the information in a specific region of DNA is being transcribed into the slightly different language of RNA (uracil has replaced thymine)

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3
Q

where does transcription take place?

A

nucelus

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4
Q

genes are transcribed to what?

A

mRNA

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5
Q

how is the process of pre-mRNA initiated?

A

unwinding a specific portion of the DNA double-helix and the binding of RNA polymerase to a sequence at the start of the gene called the promoter region

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6
Q

what is elongation?

A

RNA polymerase adds the appropriate nucleotides (adenine, uracil, guanine, and cytosine) to elongate the pre-mRNA

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7
Q

true or false: RNA nucleotides are only added in the 5’-3’ direction

A

true

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8
Q

what is the result of RNA nucleotides added in the 5’-3’ direction?

A

the pre-mRNA that is produced has the same nucleotide sequence as the complementary strand of DNA, except that each thymine will be replaced by uracil.

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9
Q

what is termination?

A

RNA polymerase reaches the terminator sequence and the pre-mRNA is released from the DNA

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10
Q

true or false: in bacterial cells, the pre-mRNA is ready to leave the nucleus

A

true

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11
Q

what 3 things must occur before non-bacterial cells’ pre-mrna can leave the nucleus?

A

1) a special cap has to be added to the 5’ end 2) a tail has to be added to the 3’ end
3) RNA sequences that aren’t going to be included in the final version of the protein made in the cytoplasm have to be removed.

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12
Q

what is the 5’ cap?

A

a modified guanine nucleotide that is involved in getting the mRNA out of the nucleus

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13
Q

what does the 3’ tail consist of?

A

a series of adenine nucleotides and is called a poly-A tail

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14
Q

what does the cap and tail protect the ends of the mRNA from?

A

exonucleases

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15
Q

what are the “non-sense” sequences?

A

introns

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16
Q

what are the sequences that are important for making the protein?

A

exons

17
Q

what is splicing?

A

processes responsible for removing the introns from pre-mRNA to yield mRNA

18
Q

what does a spliceosome consist of?

A

short nuclear RNAs and some associated proteins

19
Q

describe the process of how a spliceosome is formed

A

The short nuclear RNAs attach to the ends of the exons on either side of an intron and then move together

20
Q

what happens to the introns when the formation of a spliceosome forms?

A

intervening intron forced into a loop

21
Q

what happens as the spliceosome tightens?

A

the ends of the exons are linked together and the intron is released

22
Q

why can the introns be rapidly degraded by the nuclear exonucleases?

A

because it lacks a cap or polyA tail

23
Q

what are the nucleotides in the introns released and used for?

A

subsequent reactions

24
Q

describe the process of alternative splicing

A
  • the short nuclear RNAs attach to the ends of exons separated by more than one intron.
  • As the spliceosome forms, this simultaneously results in the excision of both introns and exons.
  • the sequence of nucleotides in the mRNA that leaves the nucleus results in the production of a different protein than if just introns had been removed.
25
Q

what is the advantage to genes if alternative splicing is used?

A

allows the genes to be more flexible and adaptable when it comes to the proteins the cell produces

26
Q

why are exons called exons?

A

exit the nucleus where they can be expressed.

27
Q

summary:

A

, the first arrow, transcription, consists of three phases: initiation, elongation and termination. The end result is a pre-mRNA transcript whose nucleotide sequence was determined by the nucleotide sequence in the specific region of DNA from which it was transcribed. So, if part of the DNA sequence was AGACGA, the corresponding part of the mRNA will have the following sequence UCUGCU; a U for every A, and a C for every G. The pre-mRNA then is processed, either by the ‘normal’ splicing approach or the alternative splicing approach, depending on the needs of the organism (i.e., you!).

28
Q

true or false: transcription is DNA -> mRNA

A

true

29
Q

where do RNA polymerase attach to?

A

promoter sequence

30
Q

what happens after RNA polymerase attaches?

A

it separates the strands and then codes for RNA

31
Q

what is the only end that RNA polymerase can add nucleotides too?

A

3’

32
Q

true or false: RNA polymerase only adds information or codes complementary information to one side

A

true

33
Q

which side is the RNA polymerase interacting with?

A

template strand

34
Q

when the mRNA migrates out of the nucleus, where does it go to be translated?

A

ribosome

Clinically Based Concepts II (15 decks)

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