transcription

Question 1

define transcription

Answer 1

process that makes RNA from DNA

Question 2

why is the process of transcription called it?

Answer 2

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

Question 3

where does transcription take place?

Answer 3

nucelus

Question 4

genes are transcribed to what?

Answer 4

mRNA

Question 5

how is the process of pre-mRNA initiated?

Answer 5

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

Question 6

what is elongation?

Answer 6

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

Question 7

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

Answer 7

true

Question 8

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

Answer 8

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.

Question 9

what is termination?

Answer 9

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

Question 10

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

Answer 10

true

Question 11

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

Answer 11

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.

Question 12

what is the 5’ cap?

Answer 12

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

Question 13

what does the 3’ tail consist of?

Answer 13

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

Question 14

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

Answer 14

exonucleases

Question 15

what are the “non-sense” sequences?

Answer 15

introns

Question 16

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

Answer 16

exons

Question 17

what is splicing?

Answer 17

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

Question 18

what does a spliceosome consist of?

Answer 18

short nuclear RNAs and some associated proteins

Question 19

describe the process of how a spliceosome is formed

Answer 19

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

Question 20

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

Answer 20

intervening intron forced into a loop

Question 21

what happens as the spliceosome tightens?

Answer 21

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

Question 22

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

Answer 22

because it lacks a cap or polyA tail

Question 23

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

Answer 23

subsequent reactions

Question 24

describe the process of alternative splicing

Answer 24

• 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.

Question 25

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

Answer 25

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

Question 26

why are exons called exons?

Answer 26

exit the nucleus where they can be expressed.

Question 27

summary:

Answer 27

, 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!).

Question 28

true or false: transcription is DNA -> mRNA

Answer 28

true

Question 29

where do RNA polymerase attach to?

Answer 29

promoter sequence

Question 30

what happens after RNA polymerase attaches?

Answer 30

it separates the strands and then codes for RNA

Question 31

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

Answer 31

3'

Question 32

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

Answer 32

true

Question 33

which side is the RNA polymerase interacting with?

Answer 33

template strand

Question 34

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

Answer 34

ribosome