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Alleles

Different forms of a gene that occupy the same position (locus) on homologous chromosomes.

Amniocentesis

A medical procedure used to collect amniotic fluid from a pregnant woman to test for genetic abnormalities in the fetus.

Aneuploidy

A condition where the number of chromosomes is not the typical set for a species, such as an extra or missing chromosome.

Barr body

The inactivated X chromosome in the cells of female mammals, visible as a dense structure in the nucleus.

Blending inheritance

An outdated theory that offspring are a blend of the traits of their parents.

Chromosomal theory of inheritance

The theory that genes are located on chromosomes, which are the basis for inheritance.

Chorionic villi sampling (CVS)

A prenatal test where a small sample of placental tissue is collected for genetic testing.

Continuous variable

A variable that can take on an infinite number of values, such as height or weight.

Cross-fertilization

Fertilization between two different individuals, leading to genetic variation.

Crossing over (recombination)

The exchange of genetic material between homologous chromosomes during meiosis, leading to new combinations of alleles.

Codominant

A genetic scenario where both alleles in a heterozygous individual are fully expressed, without one being dominant over the other.

Dominant pedigree

A pedigree in which a dominant trait appears in every generation.

Dosage compensation

A mechanism that balances the dose of X chromosome gene expression in males and females.

Dihybrid cross

A genetic cross that follows two traits simultaneously, involving organisms heterozygous for both traits.

Dominant

An allele that masks the effect of a recessive allele in a heterozygous organism.

Epigenetic inheritance

Inheritance of traits that are controlled by factors other than changes in the DNA sequence, such as DNA methylation.

Epistasis

Interaction between gene pairs where one gene can mask or modify the expression of another gene.

First filial (F1) generation

The first generation of offspring from a cross between two parental individuals.

Genetic mapping

The process of determining the location of genes on a chromosome.

Genome-wide association study (GWAS)

A study that looks for associations between specific genetic variations (SNPs) and particular diseases across a population.

Genomic imprinting

A form of inheritance where certain genes are expressed differently depending on whether they are inherited from the mother or father.

Genotype

The genetic makeup of an organism, specifically the combination of alleles it carries.

Heterozygous

Having two different alleles for a particular gene.

Homozygous

Having two identical alleles for a particular gene.

Human genome maps

Charts that show the location of genes on human chromosomes.

Incomplete dominance

A genetic scenario where the phenotype of a heterozygote is intermediate between the phenotypes of the two homozygotes.

Maternal inheritance

Inheritance of traits specifically from the mother, often associated with mitochondrial DNA.

Multiple alleles

The existence of more than two alleles for a particular gene within a population.

Multiple crossovers

When more than one crossover event occurs between homologous chromosomes during meiosis, leading to greater genetic variation.

Monohybrid cross

A genetic cross that involves one trait, where organisms are heterozygous for that trait.

Monosomy

A condition where an individual has only one copy of a particular chromosome instead of the typical two.

Nondisjunction

An error in cell division where chromosomes fail to separate properly, leading to an abnormal number of chromosomes in the resulting cells.

Parental generation

The original individuals in a genetic cross from which offspring are derived.

Pedigree analysis

A diagram used to track the inheritance of traits across generations in a family.

Phenotype

The observable physical or biochemical characteristics of an organism, determined by both genetics and the environment.

Phenotype-wide association study (PheWAS)

A study that investigates the association between a genetic variant and multiple phenotypes across a population.

Phenotypic plasticity

The ability of an organism to change its phenotype in response to environmental conditions.

Pleiotropy

When a single gene affects multiple, seemingly unrelated traits.

Polygenic inheritance

Inheritance of a trait that is controlled by multiple genes, each contributing a small effect.

Principle of independent assortment

Mendel's law stating that the alleles of different genes are distributed independently of one another during gamete formation.

Principle of segregation

Mendel's law stating that the two alleles for a gene segregate during gamete formation and are reunited at fertilization.

Punnett square

A diagram used to predict the outcome of a genetic cross by considering all possible combinations of alleles.

Recessive

An allele whose effects are masked by a dominant allele in a heterozygous organism.

Recessive pedigree

A pedigree in which a recessive trait may skip generations and reappear when two carriers have offspring.

Rule of addition

The probability rule used to calculate the likelihood of one event or another occurring (when events are mutually exclusive).

Rule of multiplication

The probability rule used to calculate the likelihood of two independent events occurring together.

Second filial (F2) generation

The offspring of the F1 generation in a genetic cross.

Sex chromosomes

Chromosomes that determine the sex of an organism (e.g., X and Y chromosomes in humans).

Self-fertilize

When an organism fertilizes itself, commonly seen in plants.

Sex-linked (X-linked) inheritance

The pattern of inheritance for genes located on the X chromosome, which often results in different traits being expressed in males and females.

Short tandem repeats (STR)

Short sequences of DNA that are repeated in a row and vary in length between individuals, often used in genetic profiling.

Single-nucleotide polymorphisms (SNPs)

Variations at a single nucleotide position in the DNA sequence among individuals.

Testcross

A cross between an individual with a dominant phenotype but unknown genotype and a homozygous recessive individual to determine the unknown genotype.

Trisomy

A condition where an individual has an extra copy of a chromosome, resulting in three copies instead of the typical two.

Three-point testcross

A genetic cross involving three genes to map their relative positions on a chromosome.

True-breeding

Organisms that, when self-fertilized, produce offspring with the same traits over many generations.

X inactivation

The process by which one of the two X chromosomes in female mammals is randomly inactivated to prevent overexpression of X-linked genes.

Adaptor Protein

Proteins that facilitate interactions between other proteins by linking them together in cellular signaling pathways.

Antiparallel Configuration of DNA

A structural arrangement in DNA where two strands run in opposite directions: one 5' to 3' and the other 3' to 5'.

Autophosphorylation

A self-activation process where a kinase enzyme adds a phosphate group to itself, enhancing its function in signaling.

Bacteriophages (Phages)

Viruses that specifically infect bacterial cells, using them to replicate.

Cell Surface Receptors

Proteins located on the cell membrane that bind to external molecules, initiating intracellular responses.

Chargaff's Rule

A principle that states DNA from any cell should have equal amounts of adenine and thymine, and cytosine and guanine.

Chemically Gated Ion Channels

Ion channels that open in response to the binding of a specific chemical messenger.

Clamp Loader

A protein complex that loads the sliding clamp onto DNA, facilitating DNA polymerase attachment during replication.

Coactivators

Molecules that increase gene transcription by binding to transcription factors, enhancing their function.

Conservative Model of DNA Replication

A proposed model where parental DNA remains intact and produces an entirely new copy during replication.

Cyclic AMP (cAMP)

A secondary messenger involved in transmitting signals within cells, important in many biological processes.

Cyclic Guanosine Monophosphate (cGMP)

A secondary messenger similar to cAMP, often involved in signaling pathways related to vision and vasodilation.

Dephosphorylation

The removal of a phosphate group from a molecule, often regulating protein activity.

Deoxyribose Sugar

A five-carbon sugar molecule found in DNA, lacking an oxygen atom at the 2' position.

Direct Contact

A method of cell communication where cells are physically connected, allowing signal molecules to move directly between them.

Dispersive Model of DNA Replication

A proposed model where new DNA strands are mixtures of old and new segments after replication.

DNA Gyrase

An enzyme that relieves strain while double-stranded DNA is being unwound by helicase during replication.

DNA Ligase

An enzyme that joins DNA fragments by forming phosphodiester bonds, essential in DNA replication and repair.

DNA Polymerase

An enzyme responsible for synthesizing new DNA strands by adding nucleotides to a pre-existing strand.

DNA Polymerase Delta (Pol δ)

A DNA polymerase enzyme that primarily synthesizes the lagging strand during DNA replication in eukaryotes.

DNA Polymerase Epsilon (Pol ε)

An enzyme responsible for synthesizing the leading strand during DNA replication in eukaryotes.

DNA Polymerase I (Pol I)

A DNA polymerase in prokaryotes that removes RNA primers and fills in nucleotides during DNA replication.

DNA Polymerase II (Pol II)

A DNA repair enzyme in prokaryotes that also assists with the replication of damaged DNA.

DNA Polymerase III (Pol III)

The primary enzyme responsible for DNA synthesis in prokaryotic organisms.

DNA Primase

An enzyme that synthesizes RNA primers, initiating DNA synthesis.

DNA Replication

The process by which a cell duplicates its DNA, producing two identical DNA molecules.

Elongation

The phase in DNA replication where DNA polymerase extends the new DNA strand.

Endocrine Signaling

A form of long-distance signaling where hormones are released into the bloodstream to reach distant cells.

Endonuclease Activity

The ability of an enzyme to cleave the phosphodiester bond within a nucleotide chain.

Enzymatic Receptors

Receptors that have enzymatic activity and catalyze reactions upon binding to a ligand.

Excision Repair

A DNA repair mechanism that removes and replaces damaged DNA segments.

Exonuclease Activity

The ability of enzymes to remove nucleotides from the ends of DNA or RNA chains.

Initiation

The first step of DNA replication where enzymes unwind the DNA and prepare it for synthesis.

Inositol Phosphates

A group of molecules that function as secondary messengers, relaying signals within cells.

Intracellular Receptor

A receptor located inside the cell that binds to signaling molecules able to pass through the cell membrane.

G-Coupled Receptors

A family of cell surface receptors that activate G proteins to transmit signals inside the cell.

G Protein

A protein that binds to GTP and transmits signals from receptors on the cell surface to other cellular targets.

Helicases

Enzymes that unwind the DNA double helix, essential for DNA replication and repair.

Kinase Cascade

A series of protein kinases that sequentially activate each other to amplify cellular signals.

Lagging Strand

The DNA strand synthesized discontinuously in small fragments (Okazaki fragments) during replication.

Leading Strand

The DNA strand synthesized continuously in the direction of the replication fork.

Ligand

A molecule that binds specifically to a receptor to trigger a biological response.

Mismatch Repair (MMR)

A DNA repair mechanism that corrects errors introduced during DNA replication.