The Nucleus and DNA Replication

A set of 60 vocabulary flashcards covering key concepts related to the structure of the nucleus, DNA replication, and associated processes.

Nuclear Envelope

The double layered membrane that surrounds the nucleus and is contiguous with the endoplasmic reticulum.

Nucleolus

The most prominent structural element of the nucleus, responsible for ribosome synthesis and assembly.

Euchromatin

Less compacted, active form of chromatin where DNA is accessible for transcription.

Heterochromatin

Highly compacted form of chromatin that is generally inactive in terms of transcription.

Nuclear Pore Complex (NPC)

Structures that traverse the nuclear envelope allowing selective transport of molecules between the nucleus and cytoplasm.

DNA Replication

The process by which DNA is copied, resulting in two identical DNA molecules.

Semiconservative Replication

Each new DNA molecule consists of one old strand and one new strand.

Leading Strand

The strand of DNA that is synthesized continuously during DNA replication.

Lagging Strand

The strand of DNA that is synthesized discontinuously, creating Okazaki fragments.

Okazaki Fragments

Short DNA fragments that are synthesized on the lagging strand during DNA replication.

Primase

An enzyme that synthesizes a short RNA primer needed for DNA polymerase to initiate DNA synthesis.

DNA Polymerase

The enzyme responsible for synthesizing new DNA strands by adding nucleotides.

Telomeres

Repeated DNA sequences at the ends of eukaryotic chromosomes that protect against degradation.

Telomerase

An enzyme that lengthens telomeres, allowing for continued cell division.

Ran G-protein

A protein that plays a key role in nuclear transport by forming a gradient between the nucleus and cytoplasm.

Histones

Proteins that package and order DNA into structural units called nucleosomes.

Nucleosome

A structural unit of chromatin formed by DNA coiling around a histone octamer.

Chromatin

The complex of DNA and proteins that forms chromosomes within the nucleus.

Transcription Factors

Proteins that help regulate the transcription of DNA into RNA by binding to specific DNA sequences.

RNA Primer

A short strand of RNA that serves as a starting point for DNA synthesis.

DNA Methylation

The addition of a methyl group to DNA, which can affect gene expression.

Unwinding

The process where the double helix of DNA separates to allow replication.

Gyrase

An enzyme that alleviates the tension ahead of the replication fork during DNA unwinding.

Ligation

The process of joining two DNA strands together, sealing nicks in the sugar-phosphate backbone.

Helicase

An enzyme that unwinds the DNA double helix during DNA replication.

Nuclear Pore

Channel that allows transport of molecules in and out of the nucleus.

Nuclear Lamina

A meshwork of protein fibers that provides mechanical support to the nuclear envelope.

Cytoplasm

The substance within a cell, excluding the nucleus, that contains organelles and cytosol.

Ribosomal RNA (rRNA)

A type of RNA that, together with proteins, makes up the structure of ribosomes.

Messenger RNA (mRNA)

RNA that serves as a template for protein synthesis.

Transfer RNA (tRNA)

RNA that brings amino acids to the ribosome during protein synthesis.

Karyopherins

Proteins that mediate the transport of nuclear proteins across the nuclear envelope.

Importins

A type of karyopherin that transports proteins into the nucleus.

Exportins

A type of karyopherin that transports proteins out of the nucleus.

Origin of Replication

The specific location where DNA replication begins.

Replication Fork

The point at which the two strands of DNA are separated to allow replication to occur.

Centromere

The region of a chromosome where sister chromatids are joined together.

Telomere Erosion

The progressive shortening of telomeres during DNA replication.

Nuclear Basket

Structural components of the nuclear pore complex that help in selective transport.

Cytoskeleton

The network of fibers in the cytoplasm that helps to maintain cell shape and structural integrity.

Nuclear Transport Signal

A signal that directs the transport of proteins into or out of the nucleus.

Guanine Exchange Factor (GEF)

A protein that facilitates the exchange of GDP for GTP on G-proteins, activating them.

GTPase Activating Protein (GAP)

A protein that stimulates the hydrolysis of GTP to GDP, inactivating G-proteins.

Epigenetics

The study of changes in gene expression that do not involve alterations to the underlying DNA sequence.

Hydroxyl Group

A functional group consisting of an oxygen atom bonded to a hydrogen atom, often involved in the structure of RNA.

Allele

A variant form of a gene that can exist at a specific locus on a chromosome.

Centrosome

An organelle that serves as the main organizing center for microtubules; involved in the cell cycle.

Phenotype

The observable physical or biochemical characteristics of an organism, determined by both genetic and environmental influences.

Genotype

The genetic constitution of an individual organism.

Aging

The gradual decline in biological function and ability that occurs over time.

Stem Cells

Undifferentiated cells with the potential to develop into many different cell types.

Cell Senescence

The process by which cells stop dividing and enter a state of permanent growth arrest.

Proteins

Large biomolecules composed of amino acids that perform a variety of functions in organisms.

Biochemical Activity

The chemical processes and transformations that occur within a living organism.

Disease

An abnormal condition of a living organism that impairs bodily functions, often due to infection, genetic defect, or environmental stress.

Tumor Suppressor

A gene that protects a cell from one step on the path to cancer.