Unit 3 - Transcription (DNA and RNA synthesis)

Question 1

Transcription 3 process

Answer 1

1) initiation
2) elongation
3) termination
-occurs in nucleus + DNA is chemically rewritten as an RNA code

Question 2

simple Initation

Answer 2

RNA polymerase binds to the DNA and unwind it

Question 3

Elongation simple

Answer 3

RNA polymerase creat a complementary mRAN strand. it + on ribonucleotides in 5’ to 3’ direction

Question 4

Termination simple

Answer 4

translation ceases, and the mRNA is relesed

Question 5

STRAND terms

Answer 5

template strand = used as a template
coding stand = not used as a template

Question 6

Initiation in depth

Answer 6

RNA polymerase enzyme used to synthesize an RNA stran while using DNA as a template and needs no primer

Question 7

RNA polymerase

Answer 7

• binds to the promoter region located upstream of the gene
• and unzips the double strand in order to expose the bases

Question 8

Promoter

Answer 8

a nucleotide sequence that lies just before a gene and allows for the binding of RNA polymerase
- high inn A=T bp
- only two H-bonds = easy to break needing less energy needed

Question 9

TATA Box

Answer 9

a section of DNA with a high % of T and A bases, which recognized by RNA polymerase
Eukaryotes = TATA
Prokaryotes = TATAAT

Question 10

two steps of initation

Answer 10

1) binding to promoter
2) unzipping the DNA

Question 11

Elongation in depth

Answer 11

builds mRNA strand
- incorporates ribonucleotides that r complementary to template DNA (catalyzes the formation of phosphodiester bonds)
- no primer
- 5’ to 3’
- promoter does not get transcribed

Question 12

where r mRNA found(+)

Answer 12

at 3’ end

Question 13

which enzyme initiates transciption

Answer 13

RNA polymerase

Question 14

RNA is synthesized from strand of DNA

Answer 14

DNA template strand

Question 15

Termination in depth

Answer 15

• The terminator sequence is located at the end of the gene
• recognizes the terminator sequence (AAUAA) + releases mRNA strand
• transcription stops (DNA rewinds itself)

Question 16

After transcription

Answer 16

• mRNA will exit nucleus
• transcription of mRNA = protein in cytoplasm

Question 17

post transcriptional modification

Answer 17

• newly built mRNA but must be modified bf leaving the nucleus
• remove non-coding regions
• • Protect the mRNA from cytoplasmic nucleases and phosphates

Question 18

3 modifications

Answer 18

1) splicing
2) add 5’ cap
3) add poly-A tail

Question 19

Splicing

Answer 19

removal of non coding regions (introns) in the transcript
a) excise the introns
b) ligate exons
c) degraded in the nucleus

Question 20

3 splicing steps

Answer 20

1) small nuclear RiboNucleoProteins bond together to from splicesome

2) splicesome loops the intron bringing the exon close together

3) intron is cute and removed

Question 21

5’ cap

Answer 21

made of 7-methyl guanosine
- protects mRNA from digestion by enzymes
- ribosomes recognizes this site as initial attachment

Question 22

Poly (A) tail

Answer 22

• 200 A nucleotides r added to 3’ end of mRNA
• catalyzed by poly-a-polymerase
• prevent degradation
• aids in export from nucleus

Question 23

quality control

Answer 23

• no proofreading mechanisms
• more errors in transcription than replication
• redundancy of the genetic code

Question 24

first major step in transcription

Answer 24

recognition of the promoter sites

Question 25

T or F
during initiation of transcription, RNA polymerase binds to the promoter region

Answer 25

T

Question 26

T or F
RNA polymerase transcribes both strands of DNA at the same time

Answer 26

F

Question 27

what is added to the 3’ end of mRNA

Answer 27

a poly-A-tail