BIOL 2030 Lecture Notes - Lecture 13: Small Interfering Rna, Microrna, Gene Expression

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3 May 2018

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Prokaryotic and Eukaryotic Transcription

February 22, 2016

Gene Expression and the “Central Dogma”

• Transcription + translation = expression

• Gene expression is simpler in prokaryotes ** no RNA processing

• mRNA = protein coding RNA

Overview of Transcription

• all RNA is transcribed from DNA

• Eukaryotes only – pre-mRNA, snRNA, sno,RNA, miRNA, siRNA, piRNA

• Prokaryotes only – crRNA

• Both – mRNA, rRNA, tRNA

• Involves the selective synthesis of RNA

• Not all DNA is transcribed in a given cell

• Synthesis is complementary and antiparallel to the DNA template strand

Transcription

• A single strand of the double helix is used as a template

• Template is read from 3’ to 5’

• Chain synthesis begins de novo

• Ribonucleotides are added to 3’ OH group of growing RNA

• RNA is synthesized from 5’ to 3’

• Numerous RNA molecules are transcribed simultaneously from each DNA strand

Replication

• Both strands

• Whole genome

• Only once

• New nucleotide chain grows from 5’  3’

• Requires upstream 3’ OH to start

Transcription

• 1 strand

• selected sequences

• many times/cycles

• new nucleotide chain from 5’  3’

• no requirement for 3’ OH

Requirements for Transcription

• RNA nucleotides

• DNA template

• RNA polymerase

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Document Summary

Gene expression and the central dogma : transcription + translation = expression, gene expression is simpler in prokaryotes ** no rna processing, mrna = protein coding rna. Replication: both strands, whole genome, only once, new nucleotide chain grows from 5" 3", requires upstream 3" oh to start. Transcription: 1 strand, selected sequences, many times/cycles, new nucleotide chain from 5" 3", no requirement for 3" oh. Requirements for transcription: rna nucleotides, dna template, rna polymerase. Up and down mutations of promoters: down mutation weakens (-35, up mutation strengthens (-10, the more similar the actual sequence is to the consensus, the stronger the promter should be. Prokaryotic rna polymerase: sigma factor help in the recognition of multiple classes of promoters, holoenzyme = complete enzyme complex composed of core rna polymerase and sigma factor, without sigma, core enzyme initiates transcription randomly. Initiation and elongation: synthesized from 5" to 3". Transcription ends after the terminator sequence is transcribed.

Related Questions

Which type of RNA is unique to eukaryotes?

		mRNA
		rRNA
		tRNA
		snRNA
		Its a trick, all cells have all four types of RNA.

1 points

QUESTION 2

The region of DNA to which RNA polymerase binds to initiate transcription is the:

		origin
		promoter
		enhancer
		none of the above are correct

1 points

QUESTION 3

Holoenzyme:

		is RNA polymerase core enzyme.
		is sigma factor.
		is core plus sigma factor.
		none of the above are correct.

1 points

QUESTION 4

Which of these is formed FIRST when RNA polymerase binds to a promoter?

		The closed promoter complex
		The open promoter complex
		A rho-independent terminator
		none of the above are correct.

1 points

QUESTION 5

A hairpin loop followed by a run of Us:

		is the sequence formed in the sense strand of a gene using a rho-independent terminator.
		is the sequence recognized by the rho protein.
		is the structure formed in RNA that causes rho-independent termination.
		is formed immediately after the open promoter complex is formed.

1 points

QUESTION 6

RNA polymerase:

		reads the template strand of the DNA in the 3' to 5' direction.
		synthesizes the RNA in the 5' to 3' direction.
		can begin transcription without a primer.
		all of the above are correct.

1 points

QUESTION 7

Which of the following statements is FALSE?

		Bacteria like E. coli have only one type of sigma factor.
		RNA polymerase has no proofreading activity.
		The promoter of a gene is upstream of the RNA-coding region.
		Bacterial transcriptional terminators are copied into RNA to cause termination.

1 points

QUESTION 8

If the template strand of a gene has the sequence 5' ATGCGAT 3', then:

		the RNA produced will have the sequence 5' AUGCGAU 3'.
		the RNA produced will have the sequence 5' UAGCGUA 3'.
		the RNA produced will have the sequence 5' AUCGCAU 3'.
		None of the above are correct.

1 points

QUESTION 9

The sense strand:

		is the lagging strand
		is also the template strand.
		always goes left to right.
		none of the above are correct.

1 points

QUESTION 10

Which of these is transcribed but not translated?

		mRNA
		tRNA
		rRNA
		all of the above
		tRNA and rRNA are transcribed but not translated.

please help i am a bit confused

BIOCHEM QUESTIONS:

Question 1) (1.5 points) True or false: The initial native DNA is usually in an overwound state, making the initial strand separation during replication energetically favorable, with continued strand separation at the replication fork resulting in underwound DNA that is then fixed by DNA gyrase.

Question 2) (1.5 points) True or false: UV based DNA damage largely causes dimerization of C and T bases that are fixed by the NER DNA repair pathway.

Question 3) (1.5 points) True or false: There is no enzyme within humans that has a reverse transcriptase activity.

Question 4) (1.5 points) True or false: One reason why uracil is not observed in DNA is that deamination of cytosine would result in Uracil and therefore potentially changing a GC base bp to an AT bp after a couple of rounds of replication.

Question #5: (1 point) Which of these statements is correct about the RNA polymerase? a) It makes tRNA, mRNA and rRNA b) It uses an RNA template c) It uses ATP, CTP, GTP and TTP d) It requires a primer

Question #6: (1 point) RNA polymerase grows the RNA chain in the 3â to 5â direction. a) True b) False

Question #7: (1 point) The mRNA is copied from the template strand. The mRNA has the exact same nucleotide sequence of the non-template strand except for U instead of T. a) True b) False

Question #8: (1 point) Only a limited portion of the DNA strand is copied by RNA polymerase, and there are initiation and termination signals for transcription. a) True b) False

Question #9: (1 point) The hairpin loop is the only way to conduct transcription termination in Prokaryotes. a) True b) False

pinkkangaroo550

1. What reaction is catalyzed by reverse transcriptase and used in the laboratory to generate cDNA?

a. transcription of RNA to DNA

b. transcription of DNA to RNA

c. conversion of ribonucleotides into deoxyribonucleotides

d. translation of RNA to DNA

e. conversion of a ribonucleotide to a DNA double helix

2. In eukaryotic cells, _________determine the amount of mRNA arising from a particular gene.

a. transcriptional-level controls

b. RNA processing-level controls

c. translational-level controls

d. replication-level controls

e. b and c

3. In eukaryotic cells, _________determine how a primary transcript is converted to mature mRNA

a. transcriptional-level controls

b. RNA processing-level controls

c. translational-level controls

d. replication-level controls

e. a and d

4. In eukaryotic cells, _________determine when a particular mRNA is actually used in protein synthesis.

a. transcriptional-level controls

b. RNA processing-level controls

c. translational-level controls

d. replication-level controls

e. None of the above because protein synthesis takes place immediately

5. Under what circumstances do cells selectively activate and suppress their genes?

a. at different stages of embryonic development

b. in different tissues

c. exposure to different types of stimuli

d. No such circumstances exist in natureâcells express all their genes throughout life.

e. a, b and c

6. Which statement about the control of gene expression is FALSE?

a. A single gene may be controlled by different transcription factors.

b. A single transcription factor may be necessary for the expression of different genes.

c. Each cell type has a characteristic pattern of gene transcription, which is determined by the particular complement of transcription factors contained in that cell.

d. Expression of protein genes is primarily controlled in nucleoli

e. Control of gene transcription is complex and influenced by various circumstances.

7. What is thought to maintain X chromosome inactivation in females?

a. DNA acetylation

b. DNA methylation

c. RNA inactivation

d. Histone methylation

e. None of the above because both X chromosomes are active in females and males.

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BIOL 2030 Lecture Notes - Lecture 13: Small Interfering Rna, Microrna, Gene Expression

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