BLG 143 Study Guide - Final Guide: Precursor Mrna, Spliceosome, Phosphodiester Bond

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16.2 RNA Processing in Eukaryotes

The information in DNA is not directly converted to mRNA.

When a eukaryotic gene is transcribed, the product is an immature primary RNA transcript.

Before primary transcripts can be translated, they have to be processed in a complex series

of steps.

Exons  regions of eukaryotic genes that’re part of the final mRNA

Introns  sections of primary transcript in mRNA; the reason why eukaryotic genes are

much longer than their corresponding mature RNA transcripts

RNA Splicing

The transcription of eukaryotic genes by RNA polymerase generates a primary RNA

transcript that contains both the exon and intro regions.

As transcription proceeds, the introns are removed from the growing RNA strand by

splicing.

Pieces of the primary transcript are removed and the remaining segments are jointed

together.

The molecule passes through into mediate stages called precursor mRNA.

When the molecule contains only exons, it’s called a mature mRNA or just mRNA.

Splicing is catalyzed by complexes of proteins and specialized RNAs called small nuclear

RNAs. These proteins-plus-RNA complexes are known as small nuclear ribonucleoproteins.

1. Begins when snRNPs bind to the 5’ exon-intron boundary and to a key adenine

ribonucleotide near the end of the intron

2. When snRNPs are in place, other snRNPs arrive to form a multi part complex called

a spliceosome. The spliceosome are the most complex molecular machines known

(in humans, 145 different proteins and RNAs)

3. Intron forms a loop when the 5’ end is covalently attached to a key adenine at its

connecting point

4. Loop is cut out and a phosphodiester bond links the exons on either side making a

contiguous coding sequence

The excised intron is degraded to ribonucleotide monophosphates.

Adding Caps and Tails to Transcripts

1. As soon as the 5’ end of a eukaryotic RNA emerges from RNA polymerase, enzymes

add 5’ cap. The cap consists of 7-methylguanylate and 3 phosphate groups.

2. An enzyme cleaves the ’ end of most RNAs once transcription is complete, and

another enzyme adds a long row of 100-250 adenine nucleotides, not encoded on

the DNA template strand, known as the poly(A) tail.

With the addition of the cap and tail and completion of splicing, processing of the primary

RNA transcript is complete. The product is a mature mRNA.

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Document Summary

The information in dna is not directly converted to mrna. When a eukaryotic gene is transcribed, the product is an immature primary rna transcript. Before primary transcripts can be translated, they have to be processed in a complex series of steps. Exons regions of eukaryotic genes that"re part of the final mrna. Introns sections of primary transcript in mrna; the reason why eukaryotic genes are much longer than their corresponding mature rna transcripts. The transcription of eukaryotic genes by rna polymerase generates a primary rna transcript that contains both the exon and intro regions. As transcription proceeds, the introns are removed from the growing rna strand by splicing. Pieces of the primary transcript are removed and the remaining segments are jointed together. The molecule passes through into mediate stages called precursor mrna. Splicing is catalyzed by complexes of proteins and specialized rnas called small nuclear. These proteins-plus-rna complexes are known as small nuclear ribonucleoproteins.

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The function of tRNA is to

Select one:

a. provide a site for polypeptide synthesis

b. transport amino acids to the ribosome

c. transcribe DNA

d. transform DNA

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The lipid bi-layer is

Select one:

a. hydrophilic

b. hydrophobic

c. hydrophilic and hydrophobic

d. depends on the surrounding medium

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Which of the following statements is FALSE?

Select one:

a. carbohydrates are generally hydrophilic molecules.

b. living things use carbohydrates for structure and for energy storage.

c. carbohydrates are composed principally of carbon, hydrogen, and oxygen.

d. none of the above â they are all true

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Which of the following terms correctly describes a compound featuring more than one double bond?

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a. saturated

b. polyunsaturated

c. monounsaturated

d. disaturated

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Eukaryotic mRNA transcripts are protected from modification by

Select one:

a. 5' caps

b. 5' poly-A caps

c. 3' caps

d. 5'-3' poly tails

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The methods of membrane transport that don't require protein channels or carriers are

Select one:

a. osmosis

b. diffusion

c. phagocytosis

d. exocytosis

e. all of the above

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Complete the following sentences: "Primary active transport is dependent on __________. Secondary active transport is dependent on __________ created by __________.

Select one:

a. channel proteins, electrochemical gradient, carrier proteins

b. electrochemical gradient, ATP, mitochondria

c. electrochemical gradient, ATP, primary active transport

d. ATP, electrochemical gradient, primary active transport

e. carrier proteins, electrochemical gradient, channel protein

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Which of the following is a reduced compound?

Select one:

a. CO2

b. O2

c. N2

d. NAD +

e. NADH

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Gel electrophoresis separates DNA fragments according to their:

Select one:

a. base sequence

b. size

c. percentage of labelled nucleotides

d. electrical charge

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G0 is:

Select one:

a. part of interphase

b. the phase of the cell cycle where DNA replication occurs

c. the phase of the cell cycle where two identical daughter cells are created

d. a special "resting" phase in which cells are in a non cycling state

e. a special phase where the number of chromosomes in a parent cell is reduced by half such that each daughter cell contains only one member of a pair of homologous chromosomes

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At which pH will the concentration of hydrogen ions be equal to the concentration of hydroxide ions?

Select one:

a. pH 1

b. pH 5

c. pH 7

d. pH 9

e. pH 14

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Which of the following enzymes has proofreading activity?

Select one:

a. Ligase

b. Helicase

c. Topoisomerase

d. DNA polymerase

e. Peptidyl transferase

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The process of _______________ cuts introns from the primary transcript and the final "processed" mRNA is produced.

Select one:

a. RNA cleaving

b. RNA translocation

c. RNA elongation

d. RNA splicing

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Transcription is initiated when RNA polymerase binds to

Select one:

a. a promoter

b. an initiator

c. a transciptor

d. a codon

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Complete the following sentences: "__________ connect the extracellular matrix with microfilaments. __________ connect intermediate filaments from adjacent cells."

Select one:

a. Cadherins, Integrins

b. Connexins, Cadherins

c. Integrins, Cadherins

d. Integrins, Connexins

e. Connexins, Integrins

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Which of the following regions of RNAs are translated?

Select one:

a. 5' UTR

b. exons

c. introns

d. 3' UTR

e. poly-A

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Control of gene expression in eukaryotic cells occurs at which level(s)?

Select one:

a. only the transcriptional level

b. epigenetic and transcriptional levels

c. epigenetic, transcriptional, and translational levels

d. epigenetic, transcriptional, posttranscriptional, translational, and posttranslational levels

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Cellular organelles containing hydrolytic enzymes are called:

Select one:

a. peroxisomes

b. lysosomes

c. ribosomes

d. mesosomes

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______ are chemicals or combinations of chemicals that take up excess hydrogen ions or hydroxide ions in order to keep the pH constant.

Select one:

a. acids

b. bases

c. salts

d. buffers

e. carbohydrates

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Which of the following proteins appear in some stages of the cell cycle and are degraded at other stages?

Select one:

a. kinases

b. cyclins

c. nucleotides

d. phosphatases

e. none of the above

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Which of the following correctly matches an organelle with its function?

Select one:

a. mitochondrion photosynthesis

b. nucleus cellular respiration

c. ribosome manufacture of lipids

d. lysosome movement

e. central vacuole storage

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What is the sequence corresponding to the following electropherogram obtained by Sanger sequencing (green: A; red:T; black: G; blue: C)?

Select one:

a. CCGTTATGAAC

b. GGCTTATGAAG

c. CAACTATTGCC

d. GGCAATAGTTG

e. CCGTTATCAAC

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Which of the following statement is true

Select one:

a. the two DNA strands are parallel and complementary

b. the two DNA strands are anti parallel and non-complementary

c. the two DNA strands are anti-parallel and complementary

d. none of these

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The energy-requiring process by which small molecules are joined to form larger molecules is specifically called

Select one:

a. metabolism

b. anabolism

c. catabolism

d. enzymatic reactions

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When DNA replication starts

Select one:

a. the phosphodiester bonds between the adjacent nucleotides break

b. the bonds between the nitrogen base and deoxyribose sugar break

c. the leading strand produces Okazaki fragments

d. the hydrogen bonds between the nucleotides of two strand break

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A(n)_______ is the movement of a segment of a chromosome from one chromosome to another nonhomologous chromosome

Select one:

a. inversion

b. translocation

c. deletion

d. duplication

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Complete the following sentences: "Replication forks from the same origin of replication extend __________. __________ DNA strand is used as template for the leading strand at one fork and for the lagging strand at the second fork. New DNA is synthesized from 5' to 3' on the __________."

Select one:

a. unidirectionally, A different, both the leading and lagging strands

b. bidirectionally, The same, leading strand

c. bidirectionally, The same, lagging strand

d. unidirectionally, A different, leading strand

e. bidirectionally, The same, both the leading and lagging strands

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Manufacturing recombinant DNA molecules involves cutting a gene from its normal location, inserting it into a circular piece of DNA from a bacterial cell, and then transferring the circle of DNA to cells of another species. Which of the below describe the circular piece of DNA?

Select one:

a. restriction enzyme

b. plasmid

c. bacteriophage

d. transposon

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Complete the following chemical equation to make it balanced: glycerol + ___ ? triacylglycerol + ___

Select one:

a. 3 fatty acid, 3 H2O

b. fatty acid, H2O

c. 3 OH-, 3 H+

d. 3 H2O, 3 fatty acid

e. fatty acid, 3 H2O

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Which structure is found in plant cells but not animal cells? Check all that apply.

Select one or more:

a. Cell wall

b. Chloroplast

c. Plastid

d. Central vacuole

e. Lysosomes

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BLG 143 Study Guide - Final Guide: Precursor Mrna, Spliceosome, Phosphodiester Bond

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