Cell Communication and Mutations: (32-33)

Cell signaling

The process by which cells communicate with each other using chemical messengers and receptors.

Autocrine signaling

A type of signaling where a cell targets itself.

Direct signaling

Signaling that occurs through gap junctions between adjacent cells.

Paracrine signaling

Signaling where a cell targets nearby cells.

Endocrine signaling

Signaling where a cell targets distant cells through the bloodstream.

Ligand

A chemical messenger that binds to a receptor.

Receptor

A protein that binds to a ligand and initiates a cellular response.

Cell communication receptor

Receptors that facilitate communication between cells by binding ligands.

Cell-surface/membrane receptors

Receptors located on the plasma membrane that bind hydrophilic ligands.

Internal/intracellular receptors

Receptors located inside the cell that bind hydrophobic ligands.

Signal transduction

The process by which a signal is transmitted through the cell after a receptor is activated.

Signaling pathway

A series of molecular events and interactions that lead to a cellular response.

Gene expression

The process by which information from a gene is used to synthesize a functional gene product, often proteins.

Kinase

An enzyme that catalyzes the transfer of phosphate groups to substrates, often activating them.

Phosphatase

An enzyme that removes phosphate groups from substrates.

Target cell

The cell that receives the signal from a signaling cell.

Cellular response

The outcome of signal transduction, which can include changes in gene expression, metabolism, proliferation, or cell death.

Signal amplification

The process by which a small concentration of ligand can lead to a large effect on the target cell.

Conformational change

A change in the shape of a receptor that occurs upon ligand binding, activating intracellular molecules.

Phosphorylating enzymes

Enzymes that add phosphate groups to other molecules, often involved in signal transduction.

receptor protein

the molecule to which the ligand binds, which may be on the plasma membrane or within the cell and has a unique 3D shape allowing only specific ligands to bind

signaling cell

the cell that produces the ligand

receptor activation

the binding of a molecule, such as a hormone or neurotransmitter, to a specific receptor protein on the cell surface

termination of the signal

a step that involves stopping the signaling process after the cellular response

shape changes in signal transduction

the process where ligand binding results in a conformational change in the receptor, activating intracellular signaling molecules

chemical modifications in signal transduction

the process where intracellular signaling molecules can be turned on or off using chemical modifications such as phosphorylation

phosphorylation

the addition of a phosphate group (PO43-) to residues of the amino acids serine, threonine, and tyrosine

Differentiation

The process by which cells become specialized in structure and function.

Proliferation

The process of cell division and multiplication.

Metabolic changes

Alterations in the biochemical processes within a cell.

Apoptosis

Programmed cell death that occurs in multicellular organisms.

Migration

The movement of cells from one area to another.

Secretion

The process by which substances are produced and discharged from a cell.

Contraction/Relaxation

The processes by which muscle fibers shorten or lengthen.

Signal Transduction Cascade

A series of molecular events and reactions that lead to a cellular response.

GPCR

G protein-coupled receptors that play a role in signal transduction.

cAMP

Cyclic adenosine monophosphate, a second messenger important in many biological processes.

PKA

Protein kinase A, an enzyme that modifies other proteins by chemically adding phosphate groups to them.

Intracellular receptors

Receptors found within the cell, usually in the cytoplasm or nucleus.

Cell surface/membrane receptors

Receptors localized to the plasma membrane that bind ligands extracellularly.

Hydrophobic signaling molecules

Molecules that can diffuse across the plasma membrane and interact with intracellular receptors.

Hydrophilic ligands

Molecules such as proteins that cannot diffuse across the plasma membrane and must bind to membrane receptors.

Mutation

Changes in the nucleotide sequence of a genome.

Somatic mutation

Mutations that occur in the body cells.

Germline mutation

Mutations that occur in the egg or sperm and can be passed on to offspring.

New alleles

Alleles that can be formed from germline mutations occurring in the protein-coding regions of genes.

Genetic variation

The ultimate source of genetic variation created by mutations.

Phenotype

Observable characteristics of an organism that can change due to new alleles.

Neutral mutations

Mutations that have no effect on an organism's fitness.

Deleterious mutations

Mutations that decrease an organism's fitness.

Beneficial mutations

Mutations that increase an organism's fitness and provide a selective advantage.

Mc1r gene mutation

A mutation in the Mc1r gene in rock pocket mice that can cause black fur, providing an advantage on dark backgrounds.

Silent mutation

A mutation that results in no change in the product.

Missense mutation

A mutation that changes amino acids in a protein.

Nonsense mutation

A mutation that changes a codon to a 'stop' codon.

Frameshift mutation

A mutation that changes the reading frame of the genetic code.

Base substitution

A type of mutation where one base is replaced by another.

Point mutation

A mutation that affects a single nucleotide.

Biological fitness

The ability of an organism to survive and reproduce in its environment.

Mutations

Changes in the sequence of an organism's DNA that occur rarely and randomly.

Spontaneous mutations

Mutations that occur as a result of natural processes, such as random mistakes in DNA replication.

Induced mutations

Mutations that occur due to environmental factors like chemicals, UV rays, x-rays, and viruses.

Mutagens

Environmental factors that increase the chances of a mutation occurring.

Thymine dimers

A type of DNA damage that occurs when two adjacent thymine bases on the same DNA strand form covalent bonds.

Somatic mutations

Mutations that occur in body cells, which can lead to diseases such as cancer.

Germline mutations

Mutations that occur in egg or sperm cells and can be passed on to offspring.

Alleles

Different versions of a particular gene that can arise from genetic mutations.

Melanocortin 1 receptor (Mc1R)

The gene that determines fur color in the rock pocket mouse.

Point mutations

Mutations that affect a single base pair, including substitutions and frameshift mutations.

Substitutions

A type of point mutation where one base is replaced with another.

Silent mutations

Mutations that do not change the amino acid specified by a codon and are neutral with respect to biological fitness.

Missense mutations

Mutations that change the nucleotide sequence, resulting in a change in the amino acid specified by a codon.

Nonsense mutations

Mutations that change a codon to a stop codon, leading to premature termination of protein synthesis.

Frameshift mutations

Mutations that change the reading frame of the genetic code, potentially altering all downstream amino acids.

Impact of mutations

Mutations can vary in their effects on gene structure and function, ranked from silent (least impact) to frameshift (greatest impact).

Impact ranking of mutations

Silent (no change in the product), missense (change amino acids), nonsense (change to 'stop'), and frameshift (change reading frame) ranked from greatest to least impact on the structure and function of genes and gene products.

Ultimate source of genetic variation

Mutations are the ultimate source of genetic variation because they create new alleles, or versions of a gene, that did not previously exist.

Phenotype changes

New alleles from mutations can lead to changes in an organism's phenotype, or observable traits, which can then be acted upon by natural selection.

Evolution of new species

Over time, the accumulation of mutations can lead to the evolution of new species.

Mc1r gene mutation in rock pocket mouse

Mutations in Mc1r gene can cause the rock pocket mouse to have black fur, providing an advantage on a dark background and a disadvantage on a lighter background.

Random nature of mutation

The likelihood of a mutation being beneficial or detrimental is largely a matter of chance.

Natural selection on mutations

While natural selection can act on beneficial mutations, there is no guarantee that a beneficial mutation will occur or be passed on to future generations.

Persistence of deleterious mutations

Deleterious mutations can still persist in a population at low frequencies or in heterozygous carriers.

Comic mutation type question

What type of mutation is illustrated in the comic: Frameshift or Substitution?

Detrimental mutation comparison

Which mutation is more likely to be detrimental to an organism: a frameshift or missense mutation?