L19- Gene expression: Transcription.

Question 1

what is the central dogma of life?

Answer 1

the flow of information from the DNA to RNA is named central dogma

Question 2

what are the 5 requirements of transcription?

Answer 2

1) DNA template
2) RNA nucleotides
3) RNA polymerase
4) transcriptional factors
5) requires energy

Question 3

what are the functions of the transcriptional factors?

Answer 3

1) recognizes the promoter
2) recruits the RNA polymerase to the promoter
3) initiates transcription

Question 4

what are exons and introns?

Answer 4

eons are segments of DNA that code for amino acids while introns do not code for amino acids

Question 5

what are promoters? and give 2 examples.

Answer 5

they are molecular tags found upstream of the gene and they are recognized by RNA polymerase and binds with it and with transcriptional factors.
TATA BOX: 25 BASEPAIRS UPSTREAM THE GENE
CAAT BOX: 75 BASEPAIRS UPSTREAM THE GENE

Question 6

what are enhancers and silencers?

Answer 6

they are sequence of bases that bind with transcriptional factors, upon binding they increase the chance of RNA polymerase binding with promoter and silencers have the opposite effect.

Question 7

what are activators and repressors?

Answer 7

they are proteins that bind with enhancers and silencers that increase or decrease the rate of transcription.

Question 8

describe the binding stage

Answer 8

the RNA polymerase unwinds a small segment of the DNA creating a small bubble and only 1 strand is used as a template.(antisense-noncoding)

Question 9

describe the process of initiation

Answer 9

RNA polymerase does not require primer. the first base of mRNA is always purine and the second nucleotide is added and a phosphodiester bond is formed between them.

Question 10

describe the process elongation.

Answer 10

RNA polymerase transcribes the mRNA form the 5 prime end to the 3 prime.

Question 11

poisons mushrooms?

Answer 11

the contain alpha amanatin that bind with and inhabit RNA polymerase disturbing transcription.

Question 12

describe the process of termination

Answer 12

when termination signal is reached mRNA is released and called primary transcript and require further processing

Question 13

types of RNA polymerase?

Answer 13

mRNA———-> RNA polymerase II
rRNA ———–> RNA polymerase I
tRNA ———–> RNA polymerase III
small nuclear RNA ————> combines with protein and forms spliceosome that helps in maturation of mRNA

Question 14

messenger RNA processing

Answer 14

1) capping
2) polyadenylation
3) splicing

Question 15

describe the process of capping

Answer 15

the primary transcript is capped by a modified 7-methylguanosine nucleotide this protects mRNA from nucleases and plays a role in correct assembly of mRNA with ribosome

Question 16

describe the process of polyadenylation

Answer 16

the primary transcript is trimmed by an endonuclease and another enzymes named poly a polymerase adds multiple Adenine bases at the 3 prime end. this extends the half life of the mRNA and protect against exonuclease.

Question 17

describe the process of splicing

Answer 17

the spliceosome removes the introns form the mRNA and become 1 strand of only amino acid coding segments