Bio test 3: Genes, Genetics, and Cell Division

Activator

A regulatory protein that increases gene transcription by helping RNA polymerase bind to DNA or initiate transcription.

Alternative Splicing

The process of combining different combinations of exons from the same primary RNA transcript to produce different mRNAs and proteins from one gene.

cAMP (Cyclic AMP):

A small signaling molecule that activates the catabolite activator protein (CAP), helping stimulate transcription of the lac operon when glucose levels are low.

Chemical Modification of Proteins

The addition or removal of chemical groups or molecules from proteins to change their activity, location, stability, or function.

Chromatin Remodeling Complex

A protein complex that uses energy to reposition or remove nucleosomes, changing DNA accessibility and influencing gene transcription.

Coding Region

The portion of a gene's DNA sequence that specifies the amino acid sequence of a protein, corresponding to the translated region of its mRNA

DNA-Binding Motifs

Specific structural regions of proteins that allow them to recognize and bind particular DNA sequences, helping regulate gene expression.

Double-Stranded RNA (dsRNA):

An RNA molecule consisting of two complementary strands that can trigger RNA interference and lead to the silencing of specific genes.

Enhancers

DNA sequences that bind specific transcription factors and increase transcription, sometimes from far away from a gene's promoter.

Exons

Regions of a gene that remain in the mature RNA after splicing. They generally contain protein-coding sequences, although some exons include untranslated regions.

Export Inhibition

A form of gene regulation in which a cell prevents RNA from leaving the nucleus, stopping it from being translated in the cytoplasm.

Gene

A segment of DNA containing the information needed to produce a functional product, such as a protein or functional RNA.

General Transcription Factors:

Proteins required for transcription initiation that help RNA polymerase bind to the promoter and begin transcribing a gene.

Histones

Proteins around which DNA wraps to form nucleosomes, helping package DNA and regulate access to genes.

Histone Acetylation

The addition of acetyl groups to histone proteins, usually loosening chromatin structure and making DNA more accessible for transcription.

Induction

The activation or increase of gene expression in response to a signal, often when a molecule causes a repressor to stop blocking transcription.

Initiation Complex:

The group of proteins, including RNA polymerase and transcription factors, assembled at a promoter to begin transcription.

Iac Operon

A group of bacterial genes involved in lactose metabolism that are regulated by lactose availability and glucose levels.

mRNA Editing

The alteration of an RNA molecule's nucleotide sequence after transcription, potentially changing the protein produced from it.

miRNA (MicroRNA)

A small, noncoding RNA that binds to complementary sequences in target mRNAs and reduces gene expression by inhibiting translation or promoting mRNA degradation.

Negative Control

A type of gene regulation in which a regulatory protein, usually a repressor, decreases transcription by preventing RNA polymerase from transcribing a gene.

Nucleosomes

Structures consisting of DNA wrapped around a core of histone proteins; they are the basic units of chromatin.

Operator

A regulatory DNA sequence in an operon where a repressor can bind to block transcription.

Operon

A group of bacterial genes controlled by a shared promoter and regulatory region, allowing the genes to be transcribed together into one mRNA molecule.

Positive Control

A type of gene regulation in which an activator protein increases transcription by helping RNA polymerase initiate transcription.

Post-Transcriptional Gene Regulation

The control of gene expression after RNA has been transcribed from DNA but before or during its use in protein production.

Post-Translational Gene Regulation

The regulation of protein activity or abundance after translation through processes such as protein modification, activation, or degradation.

Primary Transcript:

The initial RNA molecule produced during transcription before processing, such as splicing and modification, produces mature RNA.

Promoter

A DNA sequence where RNA polymerase and associated transcription factors bind to initiate transcription.

Proteasome

A large protein complex that breaks down proteins tagged for degradation, helping regulate protein levels and remove damaged or unnecessary proteins.

Repression

The reduction or prevention of gene expression, often when a repressor protein binds DNA and blocks transcription.

Repressor

A regulatory protein that decreases transcription by binding to a regulatory DNA sequence, such as an operator, and interfering with transcription.

RNA Polymerase

An enzyme that synthesizes RNA using a DNA template during transcription.

RNA Interference (RNAi)

A gene-silencing mechanism in which small RNAs guide cellular machinery to target mRNAs for degradation or inhibit their translation.

RNA Splicing

The process of removing introns from a primary RNA transcript and joining exons to produce mature RNA.

siRNA (Small Interfering RNA)

A short RNA molecule that guides the RNA-induced silencing complex (RISC) to complementary mRNA, often causing the mRNA to be degraded.

Small RNAs

Short RNA molecules that regulate gene expression or perform other cellular functions without being translated into proteins. Examples include miRNAs and siRNAs.

Spliceosomes

Complexes made of proteins and small nuclear RNAs (snRNAs) that remove introns from pre-mRNA and join exons together.

Specific Transcription Factors

Regulatory proteins that bind particular DNA sequences and increase or decrease transcription of specific genes in response to cellular signals.

Transcriptional Gene Regulation

The control of gene expression by regulating whether and how frequently a gene is transcribed into RNA.

Transcription Complex

The collection of RNA polymerase and associated proteins assembled at a gene's promoter to carry out transcription.

Transcription Factors

Proteins that bind DNA or interact with other transcription machinery to regulate the transcription of genes. They can act as activators or repressors.

trp Operon

A bacterial operon that contains genes needed to synthesize tryptophan. It is typically switched off when tryptophan is abundant because tryptophan activates its repressor.

Ubiquitin

A small protein that can attach to other proteins and mark them for degradation or alter their location or activity.

Ubiquitination

The process of attaching ubiquitin to a target protein. Adding a chain of ubiquitin molecules often marks a protein for degradation by the proteasome.

UTR (Untranslated Region)

A region of mRNA that is not translated into protein but can regulate mRNA stability, localization, and translation. The 5′ UTR is before the coding region, and the 3′ UTR is after it.

Daughter Cell

A new cell produced when a parent cell divides. In mitosis, two genetically similar daughter cells are typically produced.

Binary Fission

A form of asexual reproduction in prokaryotes in which a cell replicates its DNA and divides into two daughter cells.

Septum

A dividing wall that forms between two daughter cells during bacterial binary fission.

Mitosis

The process of nuclear division in eukaryotic cells that separates duplicated chromosomes into two genetically similar nuclei.

Cytokinesis

The division of the cytoplasm to form two separate daughter cells, usually following mitosis.

Contractile Ring

A ring of actin and myosin proteins that contracts to form a cleavage furrow during cytokinesis in animal cells.

Cell Plate

A structure that forms between two daughter nuclei during cytokinesis in plant cells and develops into a new cell wall separating the daughter cells.

Karyotype

An organized display of an individual's chromosomes arranged in homologous pairs according to size, shape, and banding pattern.

Haploid

A cell containing one complete set of chromosomes, represented by n. Human gametes are haploid and contain 23 chromosomes.

Diploid

A cell containing two complete sets of chromosomes, represented by 2n, with one set inherited from each parent. Most human body cells are diploid and contain 46 chromosomes.

Homologous Chromosomes

A pair of chromosomes that carry the same genes at corresponding locations but may contain different alleles. One chromosome comes from each parent.

Homolog

One member of a homologous chromosome pair.

Centromere

The chromosome region where sister chromatids are held together and where the kinetochore forms.

Kinetochore

A protein structure that assembles at the centromere and attaches chromosomes to spindle microtubules during cell division.

Sister Chromatids

Two identical copies of a replicated chromosome that remain attached until they separate during cell division.

Cohesin Proteins

Proteins that hold sister chromatids together after DNA replication until their separation during cell division.

Chromatin

The complex of DNA and associated proteins that makes up eukaryotic chromosomes.

Euchromatin

A loosely packed form of chromatin that is generally more accessible to transcription machinery and more likely to contain actively expressed genes.

Heterochromatin

A tightly packed form of chromatin that is generally less accessible to transcription machinery and associated with reduced gene expression.

Nucleosome

The basic unit of chromatin, consisting of DNA wrapped around a core of histone proteins.

Histones

Proteins around which DNA wraps to form nucleosomes, allowing DNA to be packaged and helping regulate gene expression.

10-nm Fiber

A relatively thin chromatin structure formed by nucleosomes connected by stretches of DNA, often described as a beads-on-a-string arrangement.

Solenoid

A proposed coiled arrangement of nucleosomes that describes one model of higher-order chromatin packing.

30-nm Fiber

A historically described, more compact chromatin structure formed by coiling nucleosomes. Its existence as a regular structure throughout living cells is debated.

G1 Phase

The first growth phase of the cell cycle, during which the cell grows, performs normal functions, and synthesizes proteins and organelles.

S Phase (Synthesis Phase)

The phase of the cell cycle during which DNA replication occurs, producing duplicated chromosomes consisting of sister chromatids.

G2 Phase

The growth phase after DNA replication in which the cell prepares for mitosis and checks that DNA replication has been completed correctly.

M Phase (Mitotic Phase)

The phase of the cell cycle during which mitosis and usually cytokinesis occur, producing two daughter cells.

Interphase

The portion of the cell cycle consisting of G1, S, and G2, during which the cell grows, performs normal functions, and replicates its DNA.

Centrosome

A major microtubule-organizing center in animal cells that helps organize the mitotic spindle during cell division.

Prophase

The stage of mitosis during which chromosomes condense, the mitotic spindle begins to form, and the nucleolus disappears. In many descriptions, nuclear envelope breakdown begins during late prophase or prometaphase.

Metaphase

The stage of mitosis during which duplicated chromosomes align at the middle of the cell.

Spindle Equator (Metaphase Plate)

An imaginary plane near the middle of the cell where chromosomes align during metaphase.

Anaphase

The stage of mitosis during which sister chromatids separate and move toward opposite poles of the cell.

Telophase

The stage of mitosis during which chromosomes arrive at opposite poles, begin to decondense, and new nuclear envelopes form around each set.

Cleavage Furrow

An indentation in an animal cell's plasma membrane that forms as the contractile ring tightens during cytokinesis, eventually separating the daughter cells.

Checkpoint

A regulatory control point in the cell cycle where the cell assesses conditions and determines whether it can safely proceed to the next stage.

G1/S Checkpoint

A checkpoint that determines whether the cell is large enough, has sufficient resources, and has sufficiently undamaged DNA to begin DNA replication.

G2/M Checkpoint

A checkpoint that verifies DNA replication is complete and checks for DNA damage before the cell enters mitosis.

Metaphase or Spindle Checkpoint

A checkpoint that ensures chromosomes are properly attached to spindle microtubules before sister chromatids separate during anaphase.

Growth Factor

A signaling molecule that stimulates cell growth and division by activating specific cellular signaling pathways.

Proto-oncogene

A normal gene that promotes cell growth or division when appropriately activated. Mutations or excessive expression can turn it into an oncogene.

Oncogene

A gene that promotes uncontrolled cell growth and division when abnormally activated, potentially contributing to cancer.

Tumor Suppressor Gene

A gene whose normal product helps prevent uncontrolled cell division, repair DNA damage, or trigger cell death when necessary. Loss of its function can contribute to cancer.

Meiosis

A type of cell division that reduces the chromosome number by half and produces four genetically different haploid cells from one diploid cell.

Sexual Reproduction

Reproduction involving the fusion of gametes, typically combining genetic material from two parents to produce genetically unique offspring.

Gametes

Haploid reproductive cells, such as sperm and eggs, that fuse during fertilization.

Fertilization

The fusion of two haploid gametes to form a diploid zygote.

Zygote

The diploid cell formed when two haploid gametes fuse during fertilization.

Meiosis I

The first meiotic division, during which homologous chromosomes separate, reducing the chromosome number by half.

Meiosis II

The second meiotic division, during which sister chromatids separate, producing haploid cells.

Synapsis

The pairing of homologous chromosomes during prophase I of meiosis.

Prophase I

The stage of meiosis when homologous chromosomes pair, crossing over occurs, and chromosomes condense.

Synaptonemal Complex

A protein structure that forms between homologous chromosomes during prophase I and helps hold them together during synapsis.