Genetics Exam 3

Post-translational regulatory level

Controls protein function, activity, localization, and stability after translation has occurred

Translational regulatory level

Controls how efficiently and rapidly cellular messenger RNAs (mRNAs) are translated into proteins

RNA processing regulatory level

a critical post-transcriptional regulatory level that determines how pre-mRNA is converted into mature, functional mRNA before translation

Transcriptional regulatory level

the control of the conversion of DNA into RNA determining when, where, and how much of a specific gene product is made

Epigenetic regulatory level

controls gene expression and cellular function without changing the underlying DNA sequence through reversible chemical modifications and structural changes in chromatin

Dicer

ribonuclease enzyme that cuts long double-stranded RNA and pre-microRNA into short RNA fragments

Argonaute

Protein that acts as the catalytic engine of RNA interference and microRNA pathways in eukaryotes, and functions as nucleic acid-guided endonucleases in prokaryotes

RISC complex

RNA-induced silencing complex that regulates gene expression and silences gene post-transcriptionally using small single-stranded RNA molecules

miRNA

small, single-stranded, non-coding RNA molecule that regulates gene expression after transcription

siRNA

double-stranded, non-coding RNA molecules that silences specific gene expression by degrading complementary mRNA

RNA interference

Where small RNA molecules neutralize target mRNA to silence or reduce the expression of specific genes

Alternative Splicing

regulated cellular process during gene expression where exons from the same pre-mRNA are joined in different combinations, allowing a single gene to encode multiple protein variants

Poly-A tail

A long chain of adenine nucleotides added to the 3’ end of a mRNA molecule during RNA processing that makes the mRNA more stable and precents its degradation

Splicing

molecular process where non-coding RNA segments (introns) and removed from a pre-mRNA transcript and coding segments (exons) are joined together to form mature mRNA

Introns

non-coding nucleotide sequence within a gene that’s transcribed into pre-mRNA but is removed by splicing

Exons

nucleotide coding sequence in a gene that remains in the final mature mRNA after transcription and splicing

5’ Cap

specially altered guanine nucleotide added to the 5’ end of a eukaryotic mRNA shortly after transcription begins that protects eukaryotic mRNA from degradation and helps ribosomes start protein synthesis

combinatorial control

regulatory principle in molecular biology where multiple factors work together to control the expression of a single gene

DNA looping

biological process where a protein or protein complex binds to two separate sites on a DNA molecule at the same time, causing the intervening strand of DNA to bow out into a loop

insulators

specific DNA sequence elements that act as genomic boundary markers; they organize the 3D structure of chromatin and ensure that genes are regulated independently from one another

enhancers

short region of DNA that increase the likelihood of transcription for a specific target gene

promoters

specific region of DNA located upstream of a gene that acts as a landing site for RNA polymerase and regulatory proteins to initiate transcription

DNA methylation

epigenetic mechanism that adds a chemical tag called a methyl group to DNA without changing the underlying the genetic sequence that regulates gene expression by recruiting proteins involved in gene repression or by inhibiting the binding of transcription

histone acetylation

A reversable epigenetic modification that adds a acetyl group to lysine residues on histone tails, neutralizes their positive charge, and relaxes chromatin structure to increase gene transcription

condensed chromatin

tightly packed form of DNA and histone proteins found within the cell nucleus

open chromatin

loosely packed state of DNA and histone proteins that allows cellular machinery, transcription factors, and regulatory proteins to access the genetic code

What does RNA polymerase II do?

transcribes eukaryotic protein-coding genes into mRNA and produces specific non-coding RNAs including most snRNA and miRNA

termination

final step of transcription or translation where the process stops and the newly synthesized molecule (RNA) is released

elongation

stage in DNA replication, transcription, or translation where building blocks are continuously added to a growing nucleic acid or polypeptide chain

initiation

first step of transcription or translation

chromatin access

they physical degree to which nuclear macromolecules (such as transcription factors) can contact genomic DNA

What are some differences between bacterial vs eukaryotic transcription?

Like literally everything. Cellular location, enzymes involved, and how the resulting RNA is processed

attenuation

regulatory mechanism in bacteria that causes premature termination of transcription, preventing unnecessary gene expression

How does the Lactose effect lac operon expression?

It’s absence makes expression very low

How does the Glucose effect lac operon expression?

High glucose makes expression low

How does the Repressor effect lac operon expression?

a bound repressor makes expression very low

How does the CAP-cAMP effect lac operon expression?

low CAP-cAMP makes expression low

corepressor

molecule or protein that helps turn down or shut off gene expression

trp operon

cluster of genes in bacteria that codes for enzymes needed to synthesize the amino acid tryptophan

lac Operon

set of genes in enteric bacteria that work together to transport and break down lactose

CAP-cAMP regulation

example of positive gene control in bacteria, allowing the cell to switch from using glucose to alternative energy sources (like lactose) only when glucose is scarce

allolactose

disaccharide and the inducer of the lac operon

Inducible system

molecular genetic system that is normally off and turned by the presence of a specific molecule

Repressible system

molecular genetic system that is normally on and is turned off by the accumulation of a specific molecule

regulator gene

gene that codes for a product (like a transcription factor) that controls the expression of other genes

structural genes

a DNA sequence that encodes a protein or non-coding RNA responsible for cellular structures, metabolic enzymes, or functional traits, rather than controlling the expression of other genes

operator

a regulatory DNA sequence in an Operon where a transcription factor binds to control the transcription of nearby genes

promoter

a specific region of DNA located upstream of a gene that acts as a landing site for RNA polymerase and regulatory proteins to initiate transcription

operon

functioning until of DNA in prokaryotes that contains a cluster of related genes under the control of a single promoter

rho-dependent termination

a bacterial transcription termination mechanism that requires the action of the Rho protein, an ATP-dependent hexametric RNA helicase/translocatse

rho-independent termination

a mechanism that stops bacterial RNA transcription without the help of the Rho protein, instead making a loop that eventually detaches from the DNA template

-10 promoter region

promoter region in bacteria that’s 10 base pairs upstream of the starting point

— 35 promoter region

promoter region in bacteria that’s 35 base pairs upstream of the starting point

sigma factor

protein subunit needed for the initiation of transcription in bacteria and plant chloroplasts

RNA polymerase

a core enzyme that synthesizes an RNA strand from a DNA template during transcription

transcription directionality

transcription always proceeds in a 5’ to 3’ direction for the newly synthesized RNA strand

terminator

a DNA sequence that stops transcription

template strand

the single strand of a DNA double helix that RNA polymerase uses as a guide to build a complementary RNA transcript during transcription

coding strand

the strand of DNA whose nucleotide sequence corresponds directly to the sequence of the RNA transcript (but T—> U)

RNA-coding region

The portion of a mRNA molecule that directly translates into a protein

promoter

A specific region of DNA located upstream of a gene that acts as a landing pad and “on-switch” to initiate the transcription of that gene into RNA

transcription

the first step in gene expression, where the genetic code in a DNA sequence is copied into a complementary RNA molecule by RNA polymerase

mRNA

messenger RNA, a single stranded molecule that carries genetic instructions from DNA in the cell nucleus to the cytoplasm

rRNA

type of non-coding RNA that serves as the primary structural and catalytic component of ribosomes, the protein-building factories of all living cells

tRNA

small RNA molecule that acts as an adaptor during protein synthesis, linking mRNA codons to their corresponding amino acids

snRNA

Small nuclear RNA; a class of small non-coding RNA molecules found within the nucleus of eukaryotic cells that forms the structural and catalytic core of the spliceosome to remove non-coding introns from pre-mRNA

pre-mRNA

the initial, unprocessed single-stranded RNA transcript produced by DNA transcription in the nucleus of eukaryotic cells

What are the differences between miRNA and siRNA

miRNA is Endogenous, single-stranded, its sequence complementarity is only partly required, and it inhibits translation while siRNA can be Exo or Endogenous, is double stranded, its sequence complementarity is fully required, and it inhibits cleavage