Biology Exam 4

transcription

The process where the genetic information in DNA is copied into messenger RNA (mRNA) for protein synthesis. The process by which a cell makes an RNA copy of a piece of DNA. This RNA copy, called messenger RNA (mRNA), carries the genetic information needed to make proteins in a cell.

protein

Large, complex molecules made up of amino acids that perform various functions in living organisms. Made by transcription and translation.

DNA

The molecule that carries genetic instructions for the development, functioning, growth, and reproduction of all known organisms and many viruses, consisting of two strands that coil around each other to form a double helix.

RNA

Used for protein synthesis! A nucleic acid that plays a crucial role in coding, decoding, regulation, and expression of genes, and is essential for protein synthesis.

Uracil

A nitrogenous base found in RNA that pairs with adenine and replaces thymine found in DNA.

RNA polymerase

An enzyme that synthesizes RNA from a DNA template during the transcription process.

Transcription factor

Proteins that help regulate the expression of genes by binding to specific DNA sequences. They play a critical role in initiating and regulating the transcription of RNA.

General Transcription Factor

A protein that assists RNA polymerase in binding to the promoter region of a gene to initiate transcription.

Euchromatin

A less condensed form of chromatin that is accessible for transcription and often associated with actively expressed genes.

Heterochromatin

A tightly packed form of chromatin that is typically transcriptionally inactive and often associated with gene silencing.

Histone

A protein that helps package DNA into structural units called nucleosomes, playing a crucial role in chromatin structure and regulation of gene expression.

Chromatin

The complex of DNA and proteins found in the nucleus of eukaryotic cells, which exists in two forms: euchromatin and heterochromatin, influencing gene expression and DNA replication.

Template strand

The DNA strand that serves as a guide for RNA polymerase during transcription, providing the necessary sequence for complementary RNA synthesis.

Sigma factor

A protein needed for the initiation of transcription in bacteria, it binds to RNA polymerase to form a holoenzyme that recognizes and binds to specific promoter regions on the DNA.

Template strand

The strand of DNA that is used as a template for RNA synthesis during transcription, providing the sequence for complementary RNA nucleotides.

Non-template strand

The DNA strand that is not used for RNA synthesis during transcription; it has the same sequence as the RNA transcript, except for thymine being replaced by uracil.

Antiparallel

Referring to the orientation of DNA strands, where one strand runs in the 5' to 3' direction and the complementary strand runs in the 3' to 5' direction.

Complementary base pairing

The matching of nucleotide bases in DNA or RNA, where adenine pairs with thymine (or uracil in RNA) and cytosine pairs with guanine, ensuring accurate replication and transcription.

Promoter

A specific DNA sequence located upstream of a gene that provides a binding site for RNA polymerase and initiates transcription.

Intron

Non-coding sequence of DNA that is removed during RNA processing. Introns are found between exons and are not translated into protein.

Exon

A coding sequence of DNA that is retained in the final mRNA after RNA processing. Exons are expressed in the protein synthesis process.

Splicing

The process of removing introns from pre-mRNA and joining exons together to form a mature mRNA molecule.

PolyA tail

A stretch of adenine nucleotides added to the 3' end of mRNA that protects it from degradation and facilitates export from the nucleus.

5’ cap

A modified guanine nucleotide added to the 5' end of mRNA, important for mRNA stability and initiation of translation.

tRNA

Transfer RNA that carries amino acids to the ribosome during protein synthesis, matching anticodons with codons on mRNA.

rRNA

A type of RNA that, together with proteins, makes up the ribosomes, which are the sites of protein synthesis.

codon

A sequence of three nucleotides on mRNA that codes for a specific amino acid or signals the end of translation.

anticodon

A sequence of three nucleotides in transfer RNA that pairs with a complementary codon in messenger RNA during protein synthesis.

What are the 6 properties of the genetic code?

Triplet, degenerate/redundant, non-overlapping, punctuated, unambiguous, and universal

Triplet

A set of three nucleotides in DNA or RNA that codes for an amino acid or stops signal in protein synthesis.

Degenerate/redundant

Refers to the genetic code's property where multiple codons can encode the same amino acid.

Non-overlapping

The genetic code's property where each nucleotide is part of only one codon, ensuring distinct and separate codons.

Punctuated

Refers to the genetic code's organization where sequences are clearly defined and separated by non-coding regions, allowing for distinct reading frames.

Unambigous

The characteristic of the genetic code whereby each codon specifies only one amino acid, eliminating confusion in translation.

Universal

The property of the genetic code that indicates it is the same across all known life forms, suggesting a common evolutionary origin.

Genetic code

The set of rules that define how sequences of nucleotides in DNA and RNA are translated into the corresponding amino acid sequences in proteins. It comprises codons and is fundamental to cellular function and heredity.

Release factor

A protein that binds to the ribosome during translation termination, triggering the release of the newly synthesized polypeptide chain from the tRNA.

Silent point mutation

A type of point mutation where a change in a DNA sequence does not alter the resulting amino acid sequence of the protein, due to the redundancy of the genetic code

Conservative missense point mutation

A type of point mutation where a single nucleotide change results in a codon that codes for a different amino acid, but the substituted amino acid has similar properties to the original, leading to a potentially minimal impact on protein function

Non-conservative missense point mutation

a type of mutation where a single nucleotide change results in a different amino acid being encoded. New amino acid properties are significantly different then what it was supposed to be. Can cause a change in protein function.

Nonsense point mutation

A type of point mutation that results in a premature stop codon in the amino acid sequence, leading to a truncated/shortened protein that is usually nonfunctional.

Frameshift point mutation

Occurs when insertions or deletions of nucleotides (not in multiples of three) disrupt the reading frame of a DNA sequence, leading to a completely altered protein sequence downstream of the mutation

Inducer

A molecule that triggers the expression of a gene or operon by binding to and inactivating a repressor, or by activating an activator protein, which in turn allows for the transcription of the gene

Repressor

A repressor is a protein that binds to a specific DNA sequence called the operator, which is located near the gene it regulates. By binding to the operator, the repressor prevents RNA polymerase (the enzyme that transcribes DNA into RNA) from binding to the promoter, thus preventing the transcription

Activator

A molecule or protein that increases the rate of transcription of a specific gene by binding to an enhancer or promoter region in the DNA, thus promoting gene expression

Constitutive mutants

A mutant organism where a gene product is produced continuously, meaning its expression is no longer under regulatory control, and the protein is always expressed, regardless of the presence or absence of an inducer

Lac operon

a group of genes in E. coli that are transcribed together and regulate the metabolism of lactose

operator

a DNA sequence within an operon, a unit of genetic function, that serves as a binding site for a repressor protein, thereby controlling the transcription of adjacent genes

Operon

a functional unit of genomic DNA containing a cluster of genes under the control of a single promoter, primarily found in prokaryotes, that are transcribed together into a single mRNA molecule, encoding multiple proteins with related function (aka a unit of genetic function)

allosteric regulation

a process where a molecule binds to a protein at a site other than the active site, causing a conformational change that alters the protein's activity, either enhancing or inhibiting it. (Inducers=allosteric activators, Repressors=allosteric effector)

trp operon

a group of genes that encode biosynthetic enzymes for the amino acid tryptophan. The trp operon is expressed (turned "on") when tryptophan levels are low and repressed (turned "off") when they are high. The trp operon is regulated by the trp repressor

Co-repressor

a small molecule that, when bound to a repressor protein, enhances the repressor's ability to inhibit gene transcription, effectively switching off the expression of specific genes

Chromatin

DNA and proteins, primarily histones, that makes up the structure of chromosomes within the nucleus of eukaryotic cells

Differential gene expression

biochemical process that determinates which genes respond to which signals or triggers depending on the conditions.

chromatin

a complex of DNA and proteins, primarily histones, found in the nucleus of eukaryotic cells, that condenses to form chromosomes during cell division

heterochromatin

a tightly packed, transcriptionally inactive form of DNA, often found in regions with repetitive sequences like centromeres and telomeres, that plays a crucial role in silencing genes and maintaining genome integrity

euchromatin

the less condensed, genetically active form of chromatin, containing most of the cell's functional genes and allowing for easy access for transcription

histone

fundamental proteins that package and organize DNA within the nucleus of eukaryotic cells

nucleosome

the fundamental structural unit of chromatin, the material that makes up chromosomes, consisting of DNA wrapped around a core of histone proteins

acetylation

a chemical reaction where an acetyl group (CH3CO-) is added to a molecule, often a protein or a compound

methylation

a chemical reaction that adds a methyl group to molecules, which can affect how those molecules function

core promoter

the minimal DNA sequence required for the accurate initiation of transcription by RNA polymerase II, serving as a foundational platform for gene regulation by binding transcription factors and RNA polymerase

promoter proximal elements

regulatory DNA sequences located close to the core promoter region (within a few hundred base pairs upstream of the transcriptional start site) that bind specific transcription factors, influencing gene expression

Distal regulatory regions

including enhancers, insulators, and locus control regions, are DNA sequences located far from the genes they regulate, playing a crucial role in gene expression and development

transcription factors

proteins that regulate gene expression by binding to specific DNA sequences, either promoting or inhibiting the transcription of DNA into RNA

GTFs

general transcription factors (GTFs) are proteins that, along with RNA polymerase, form the basic transcriptional apparatus, facilitating the binding of RNA polymerase to the promoter region of DNA and initiating the transcription process

mediator

a large protein complex that serves as a molecular bridge between gene-specific transcription factors bound at enhancers, and RNA polymerase II (RNA pol II).

enhancer

a DNA sequence that, when bound by specific proteins called transcription factors, increases the transcription (and therefore expression) of a gene, acting independently of orientation and distance from the gene's promote

silencer

a class of DNA elements that recruit proteins to repress transcription

insulator

a DNA sequence element that acts as a barrier, protecting genes from inappropriate signals

alternative splicing

a process where a single gene can produce multiple different mRNA transcripts, and subsequently different proteins, by combining exons in various ways, increasing the diversity of proteins from a limited number of genes

introns

non-coding DNA sequences within genes that are transcribed into RNA but are removed before the RNA is translated into a protein

exons

a sequence of DNA that is transcribed into RNA and subsequently translated into a protein

microRNAs

small, non-coding RNA molecules that regulate gene expression post-transcriptionally, typically by binding to messenger RNA (mRNA) and either inhibiting translation or causing mRNA degradation