Unit 15: Transcription and RNA Processing

Question 1

___ is first ________ to ___, then _____ is _______ to _______.

Answer 1

DNA is first transcribed to RNA, then RNA is translated to protein.

Question 2

What is DNA?

Answer 2

Stores genetic information, and transfers information to daughter cells.

Question 3

What is RNA?

Answer 3

Carries protein-encoding information, and helps to make proteins.

Question 4

What are the differences in strands between DNA and RNA?

Answer 4

DNA is generally double-stranded, while RNA is generally single-stranded.

Question 5

What are the different types of sugars in DNA versus RNA?

Answer 5

In DNA, deoxyribose is the sugar. In RNA, ribose is the sugar.

Question 6

What are the differences in bases used in DNA versus RNA?

Answer 6

DNA uses Thymine, Cytosine, Adenine, and Guanine. RNA uses Uracil, Cytosine, Adenine, and Guanine.

Question 7

What are three different types of RNA?

Answer 7

1. Messenger RNA (mRNA)
2. Ribosomal RNA (rRNA)
3. Transfer RNA (tRNA)

Question 8

What is messenger RNA (mRNA)?

Answer 8

Encodes amino acid sequence.

Question 9

What is ribosomal RNA (rRNA)?

Answer 9

Associates with proteins to form ribosomes, which catalyze protein synthesis.

Question 10

What is transfer RNA (tRNA)?

Answer 10

Transports specific amino acids to the ribosome for protein synthesis.

Question 11

In what direction is the template strand run? In what direction does it make RNA?

Answer 11

RNA polymerase reads the template strand which runs (3’→5’) to make RNA in the 5’→3’ direction.

Question 12

What is the template strand of DNA?

Answer 12

The template strand of DNA is the one that is transcribed into RNA.

Question 13

Write the sequence for the mRNA transcribed from the following template DNA sequence:
3’- A C A G T A A G C C -5’

Answer 13

5’ – U G U C A U U C G G -3’

Question 14

The ________ uses the ________ _____ of the DNA to assemble a ____________, _________ strand of
ribonucleotides

Answer 14

The polymerase uses the template strand of the DNA to assemble a complementary, antiparallel strand of
ribonucleotides

Question 15

What is the coding strand? What direction does it run in?

Answer 15

The coding strand is the side of the DNA that has the same sequence as the RNA (except it has T instead of U). Runs in the 5’ to 3’ direction.

Question 16

Transcribe the following DNA sequence on the coding strand:
5’-TTAGCGA-3’

A. 5’-AAUCGCU-3’
B. 5’-UCGCUAA-3’
C. 5’-AAUGCGU-3’
D. 5’-UUAGCGA-3’

Answer 16

D. 5’-UUAGCGA-3’
*Coding strand is complementary to the template strand and is therefore the same as the RNA strand (except Thymine changes to Uracil)

Question 17

Transcribe the following DNA
sequence on the template strand:
5’-TTAGCGA-3’

A. 5’-AAUCGCU-3’
B. 5’-UCGCUAA-3’
C. 5’-AAUCGCU-3’
D. 5’-UUAGCGA-3’

Answer 17

B. 5’-UCGCUAA-3’
Explanation- You need to reverse (flip) a DNA strand when you’re given the template strand written in the 5’ → 3’ direction, because
The template needs to be read 3’ → 5’ by RNA polymerase to build RNA in the correct direction.

Question 18

What are the four stages of bacterial transcription?

Answer 18

1. Promoter recognition
2. Transcription initiation
3. Chain elongation
4. Chain termination

Question 19

What is the +1 nucleotide?

Answer 19

The start of transcription is called the +1 nucleotide.

Question 20

Where is the promoter located in transcription?

Answer 20

The promoter is immediately upstream (5’) to the start of transcription.

Question 21

What does the promoter control?

Answer 21

The promoter controls the access of RNA polymerase to the gene.

Question 22

What does the coding region of the gene contain?

Answer 22

The coding region of the gene is the portion that contains the information needed to synthesize the protein product.

Question 23

What does the termination region of the gene regulate?

Answer 23

The termination region of the gene regulations the ending of transcription.

Question 24

Where is the termination region located?

Answer 24

The termination region is immediately downstream (3’) to the coding segment of the gene.

Question 25

What is bacterial promoter recognition?

Answer 25

It's how RNA polymerase finds and binds to the promoter region of DNA to start transcription.

Question 26

How does RNA polymerase attracted to promoters?

Answer 26

RNA polymerase is attracted to promoters by the presence of consensus sequence (common DNA sequences found on promoters).

Question 27

In bacteria, where are the two consensus sequence positions?

Answer 27

1. At the -10 position is the -10 consensus sequence. 2. At -35 is a 6-bp region, the -35 consensus sequence.

Question 28

In bacteria, RNA polymerase binds to ___ and ___ sequences and occupies the space between and around them.

Answer 28

In bacteria, RNA polymerase binds to −10 and −35 sequences and occupies the space between and around them

Question 29

If a mutation occurred at -35 in the following sequence for the lac gene decreasing the binding affinity of polymerase to the DNA, predict the effect on the rate of transcription. A. Rate of transcription would likely decrease B. Rate of transcription would likely increase C. Rate of transcription would likely stay the same D. Rate of transcription may increase or decrease

Answer 29

A. Rate of transcription would likely decrease

Question 30

What are the two steps of bacterial transcript initiation?

Answer 30

1. The RNA polymerase core enzyme and sigma subunit bind to -10 and -35 promoter consensus sequences. 2. DNA unwinds near the transcription start site to form the open promoter complex.

Question 31

What are the two steps of bacterial transcription elongation?

Answer 31

1. RNA polymerase initiates RNA synthesis. Sigma subunit dissociates after transcription initiation, core enzyme continues transcription. 2. This continues until core enzyme reaches termination sequence. DNA duplex unwinds to allow template strand direct RNA assembly but closes following synthesis.

Question 32

What are the three steps to termination of transcription?

Answer 32

Transcription terminates at the termination sequence, and the core enzyme and RNA transcript are released.

Question 33

Eukaryotic transcription compared to eukaryotic transcription: _______ ______ _______ in eukaryotes are more diverse than those in E. coli.

Answer 33

Promoter consensus sequences in eukaryotes are more diverse than those in E. coli

Question 34

Eukaryotic transcription compared to eukaryotic transcription: Eukaryotes have ______ different ___ __________ that recognize different ________ and produce different types of ____.

Answer 34

Eukaryotes have three different RNA polymerases that recognize different promoters and produce different types of RNAs.

Question 35

Eukaryotic transcription compared to eukaryotic transcription: The _________ ________ that assembles to initiate and elongate ___________ is more ________ in __________ than in bacteria.

Answer 35

The molecular machinery that assembles to initiate and elongate transcription is more complex in eukaryotes than in bacteria.

Question 36

__________ genes carry _______ and ____, and require processing to remove ______ and add caps to the ______.

Answer 36

Eukaryotic genes carry introns and exons, and require processing to remove introns and add caps to the transcript.

Question 37

Eukaryote DNA is associated with proteins to form _________; the _________ compaction affects ___________ rates.

Answer 37

Eukaryote DNA is associated with proteins to form chromatin; the chromatin compaction affects transcription rates.

Question 38

What is RNA polymerase I (RNA pol I) in eukaryotic polymerases?

Answer 38

Transcribes several ribosomal RNA genes.

Question 39

What is RNA polymerase II (RNA pol II) in eukaryotic polymerases?

Answer 39

Transcribes protein coding genes and most small nuclear RNA genes.

Question 40

What is RNA polymerase III (RNA pol III) in eukaryotic polymerases?

Answer 40

Transcribes tRNA genes, one small nuclear RNA gene, and one ribosomal RNA gene.

Question 41

What is the TATA box of eukaryotic promoter elements?

Answer 41

The most common eukaryotic promoter consensus sequence is the TATA box located at about position −25.

Question 42

What is the CAAT box of eukaryotic promoter elements?

Answer 42

A CAAT box is often found near the −80 position.

Question 43

What is the GC-rich box of eukaryotic promoter elements?

Answer 43

A GC-rich box may be located at −90, or further upstream.

Question 44

__________ ________ display a high degree of variability in type, number, and location of _________ ________ elements.

Answer 44

Eukaryotic promoters display a high degree of variability in type, number, and location of consensus sequence elements.

Question 45

The ____ box is most common, whereas the ____ box and ______ box are more variable.

Answer 45

The TATA box is most common, whereas the CAAT box and GC-rich box are more variable.

Question 46

___________ _________ elements are important for ________ of _________ factors.

Answer 46

Consensus sequence elements are important for binding of transcription factors.

Question 47

One of the functions of the 5' cap is the _________ of ______ from rapid ____________.

Answer 47

One of the functions of the 5' cap is the protection of mRNA from rapid degradation

Question 48

The second function of the 5' cap is ________ _______ of _____ out of the ________.

Answer 48

The second function of the 5' cap is facilitating transport of mRNA out of the nucleus.

Question 49

The third function of the 5' cap is facilitating subsequent ______ ______.

Answer 49

The third function of the 5' cap is facilitating subsequent intron splicing.

Question 50

The fourth function of the 5' cap is enhancing _________ efficiency by orienting the _______ on the ____.

Answer 50

The fourth function of the 5' cap is enhancing translation efficiency by orienting the ribosome on the mRNA.

Question 51

One of the functions of Poly-A Tail is facilitating _______ of mature _____ across the ______ ________ to the _______.

Answer 51

One of the functions of Poly-A Tail is facilitating transport of mature mRNA across the nuclear membrane to the cytoplasm.

Question 52

The second function of the Poly-A Tail is ________ the _____ from ___________.

Answer 52

The second function of the Poly-A Tail is protecting the mRNA from degradation

Question 53

The third function of Poly-A Tail is enhancing _________ by enabling the _______ _______ of _____.

Answer 53

The third function of Poly-A Tail is enhancing translation by enabling the ribosomal recognition of mRNA.

Question 54

The fourth function of Poly-A Tail is _______ ______.

Answer 54

The fourth function of Poly-A Tail is transcription termination.

Question 55

What is the difference between introns and extrons?

Answer 55

Exons become part of mature mRNA and encode protein segments while introns are intervening segments that are removed from pre-mRNA

Question 56

What is the purpose of tRNA?

Answer 56

tRNA binds to the complementary mRNA codon and adds the amino acid to the growing protein chain.