OIA1003 NUCLEIC ACIDS II

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Description and Tags

38 Terms

1

Transcription

The process of synthesizing RNA from a DNA template.

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2

Central Dogma of Molecular Biology

DNA → RNA → Protein, illustrating genetic information flow.

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3

RNA Polymerase

The enzyme responsible for RNA synthesis from a DNA template.

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4

Messenger RNA (mRNA)

Carries genetic instructions from DNA to ribosomes for protein synthesis.

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5

Ribosomal RNA (rRNA)

Forms the structural and functional components of ribosomes.

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6

Transfer RNA (tRNA)

Delivers amino acids to the ribosome during translation.

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7

Small Nuclear RNA (snRNA)

Involved in RNA splicing.

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8

MicroRNA (miRNA)

Regulates gene expression via RNA interference (RNAi).

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9

Template Strand

The DNA strand used by RNA polymerase for RNA synthesis.

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10

Coding (Sense) Strand

The non-template DNA strand, which has the same sequence as mRNA (except T → U substitution).

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11

Promoter Region

A specific DNA sequence where RNA polymerase binds to initiate transcription.

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12

Consensus Sequences

Conserved promoter regions:

Prokaryotes: -35 sequence (TTGACA) & Pribnow box (-10, TATAAT).

Eukaryotes: TATA box (-25), CAAT box (-75), GC box.

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13

Prokaryotic RNA Polymerase

A single RNA polymerase transcribes all RNA types.

Holoenzyme = Core enzyme + Sigma factor.

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14

Eukaryotic RNA Polymerases

RNA Pol I: rRNA synthesis (28S, 18S, 5.8S).

RNA Pol II: mRNA, snRNA, miRNA synthesis.

RNA Pol III: 5S rRNA and all tRNA synthesis.

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15

Sigma Factor (σ)

Prokaryotic transcription initiation factor, helps RNA polymerase bind to the promoter.

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16

Initiation

RNA polymerase binds to promoter, forms a transcription bubble, and starts RNA synthesis.

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17

Elongation

RNA polymerase adds ribonucleotides (NTPs) in the 5’ → 3’ direction.

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18

Termination

RNA synthesis stops when RNA polymerase reaches a termination signal.

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19

Rho-Independent Termination

RNA forms a GC-rich hairpin loop followed by a UUU sequence, causing RNA polymerase to dissociate.

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20

Rho-Dependent Termination

The Rho protein (ATP-dependent helicase) binds RNA, moves toward RNA polymerase, and separates the RNA-DNA hybrid.

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21

5’ Capping

Addition of 7-methylguanosine (m7G) to the 5’ end of mRNA for stability and ribosome recognition.

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22

3’ Polyadenylation (Poly-A Tail)

Poly(A) polymerase adds 100-200 adenine residues at the 3’ end to protect mRNA from degradation.

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23

RNA Splicing

Introns (non-coding) are removed and exons (coding) are joined by spliceosomes (snRNPs).

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24

Alternative Splicing

Allows a single gene to encode multiple proteins.

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25

RNA Editing

Modification of mRNA bases (e.g., A → I by adenosine deaminase).

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26

Nuclear Export

Mature mRNA is exported from the nucleus to the cytoplasm for translation.

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27

mRNA Stability

Poly-A tail and 5’ cap prevent degradation.

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28

Prokaryotes

Transcription occurs in the cytoplasm.

No introns, no mRNA modifications.

Polycistronic mRNA (multiple genes in one mRNA).

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29

Eukaryotes

Transcription occurs in the nucleus.

Introns must be spliced out.

Monocistronic mRNA (one gene per mRNA).

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30

Rifampin (Rifampicin)

Inhibits bacterial RNA polymerase, used for tuberculosis treatment.

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31

Actinomycin D (Dactinomycin)

Intercalates DNA, blocking transcription

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32

α-Amanitin (Toxin from Death Cap Mushroom)

Inhibits eukaryotic RNA polymerase II, causing severe hepatotoxicity.

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33

Cordycepin (3'-Deoxyadenosine)

Terminates RNA chain elongation.

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34

RNA Virus Mutations

RNA viruses mutate more frequently than DNA viruses due to lack of proofreading

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35

Examples of RNA Viruses

Ebola, Rabies, Hepatitis C, Polio, Measles, SARS-CoV-2.

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36

Ribozymes

RNA molecules with enzymatic activity, e.g., self-splicing introns.

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37

Long Non-Coding RNAs (lncRNAs)

Regulate gene expression without coding for proteins.

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38

siRNA & miRNA (RNA Interference - RNAi)

siRNA (small interfering RNA): Targets mRNA for degradation.

miRNA (microRNA): Suppresses gene expression post-transcriptionally.

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