Genetics Chapter 18

Non-coding RNAs (ncRNAs)

RNA molecules not translated into proteins.

Abundance of ncRNAs

More abundant than mRNAs in most cell types.

Transcription distribution

80% of transcription produces ncRNAs.

Scaffold function

ncRNA binds multiple proteins together.

Guide function

ncRNA directs proteins to specific cellular sites.

Alteration of protein function

ncRNA changes protein structure or stability.

Ribozyme

RNA with catalytic activity.

Blocker function

ncRNA prevents a cellular process.

Decoy function

ncRNA sequesters another ncRNA.

Long non-coding RNAs (lncRNAs)

ncRNAs longer than 200 nucleotides.

Small regulatory RNAs

ncRNAs shorter than 200 nucleotides.

MicroRNAs (miRNAs)

Small regulatory RNAs, typically 20-25 nucleotides.

Protobiont

Precursor to living cells with boundary.

RNA World

Period when RNA was primary macromolecule.

Information storage in RNA

RNA stores information in nucleotide sequences.

Self-replication of RNA

RNA replicates using itself as a template.

Catalytic activity of RNA

RNA synthesizes polypeptides and organic molecules.

Reverse transcription

RNA template used to synthesize DNA.

MicroRNA regulation

transcribed from endogenous eukaryotic genes, regulate gene expression, 60% of human genes regulated

Small interfering RNAs (siRNAs)

originate from exogenous sources, viruses or experimentally injected by researchers

RNA interference

Found in eukaryotes, mediated by miRNAs and siRNAs

Drosha and DGCR8

Complex that processes pri-miRNA.

Dicer

Enzyme that cuts pre-miRNA into siRNAs.

RNA-Induced Silencing Complex (RISC)

Complex that regulates gene expression via RNA.

Double-stranded RNA

RNA molecule 20-25 bp long from pre-miRNAs.

Processing body (P-body)

Cellular structure where RISC-mRNA complex resides.

Argonaute

Protein that cleaves mRNA in RISC complex.

siRNA

Small interfering RNA that perfectly matches mRNA.

miRNA

MicroRNA that partially complements target mRNA.

CRISPR-Cas system

Bacterial defense mechanism against bacteriophages.

CRISPR locus

Chromosomal site containing repeated sequences.

Spacer sequences

Unique DNA segments interspersed in CRISPR locus.

Cas proteins

Proteins involved in CRISPR-Cas defense mechanism.

Adaptation phase

also called spacer acquisition. Phase where spacers from bacteriophage DNA are acquired.

Expression phase

Phase where CRISPR genes are transcribed and processed.

Interference phase

Phase where crRNA guides Cas9 to target DNA.

sgRNA

Single guide RNA combining tracrRNA and crRNA.

Nonhomologous end joining (NHEJ)

Repair mechanism causing small deletions post-Cas9 cut.

Homologous recombination repair (HRR)

Repair using donor DNA to introduce mutations.

Gene editing

Experimental alteration of gene sequences.

PIWI-interacting RNA

ncRNA that inhibits transposable element movement.

Transposable elements

DNA sequences that can change position within genome.

Bacteriophages

Viruses that infect bacteria.

Mutagens

Agents that induce mutations in DNA.

Gene inactivation

Process of disabling a specific gene's function.

Point mutation

Change in a single nucleotide in DNA.

CRISPR technology applications

Used for gene editing in various organisms.

Francisco Mojica

Scientist who contributed to CRISPR-Cas discovery.

Philippe Horvath

Demonstrated CRISPR-Cas system's defense role experimentally.

Clororaphenicol

Blocks elongation by acting as competitive inhibitor of peptidyl transferase.

Erythromycin

Binds to the 23S RNA and blocks elongation by interfering with the translocation step.

Puromycin

Binds to the A site and causes premature release of the

polypeptide. This early termination of translation results in

polypeptides that are shorter than normal

Tetracycline

Blocks elongation by inhibiting the binding of aminoacyl-tRNAs to
the ribosome.

the ribosome.

Streptomycin

Interferes with normal pairing between aminoacyl-tRNAs and
codons. This causes misreading, thereby producing abnormal
polypeptides.

codons. This causes misreading, thereby producing abnormal

polypeptides.