Key Concepts in Genetics and Evolution

Nondisjunction

Failure of chromosomes to separate properly during meiosis, resulting in abnormal chromosome numbers.

Endosymbiosis

Theory that mitochondria and chloroplasts originated from prokaryotic cells engulfed by a host cell.

Ribosome

Organelle that is the site of protein synthesis (translation).

Eukaryote

An organism whose cells contain a nucleus and membrane-bound organelles.

tRNA (Transfer RNA)

Carries amino acids to the ribosome to build proteins during translation.

Semi-conservative replication

Each new DNA molecule contains one original strand and one new strand.

Vestigial structures

Structures with no current function but were useful in ancestors (e.g., human appendix).

Point mutation

A mutation that affects a single nucleotide in the DNA sequence.

Cellulose

A polysaccharide found in the cell walls of plants.

DNA sequencing

Determining the exact order of nucleotides in a DNA molecule.

Missense mutation

A point mutation that changes a codon, resulting in a different amino acid.

Divergence (Evolutionary)

When two species evolve differently from a common ancestor.

Transformation

Process in which bacteria absorb and incorporate foreign DNA from their environment.

Somatic cell mutation

A mutation that occurs in body cells (not passed to offspring).

Amphibian

Cold-blooded vertebrate that lives part of its life in water and part on land (e.g., frogs).

Phylogeny

Evolutionary history of a species or group of species.

Aves

Class of vertebrates that includes birds; characterized by feathers and hard-shelled eggs.

Comparative Embryology

Study of similarities in embryonic development among different species.

Punctuated equilibrium

Evolutionary theory stating that species evolve quickly in short bursts, followed by long periods of stability.

Restriction enzymes

Proteins that cut DNA at specific sequences.

Recombinant DNA

DNA formed by combining DNA from different organisms.

Hybrid breakdown

When offspring of hybrids are weak or sterile over generations.

Hybrid sterility

When hybrid offspring cannot reproduce (e.g., mule).

Chondrichthyes

Class of fish with cartilage skeletons (e.g., sharks, rays).

Analogous structures

Structures with similar functions but different evolutionary origins (e.g., bird and insect wings).

Sense strand

The DNA strand that has the same sequence as the mRNA (except T instead of U).

Peptidoglycan

A polymer in bacterial cell walls that provides structural support.

Transitional dating

(You may mean "relative dating" or "transitional fossils") - Fossils showing traits of both ancestral and modern species.

Uracil

Nitrogenous base found in RNA instead of thymine.

Adaptive radiation

A single ancestral species rapidly evolves into many new forms.

Mechanical isolation

Prezygotic barrier; reproductive organs are incompatible.

Temporal isolation

Prezygotic barrier; organisms breed at different times.

Silent mutation

Mutation that changes a DNA base but not the amino acid.

Eucoelomate

Animal with a true body cavity lined with mesoderm tissue.

Nonsense mutation

Mutation that changes an amino acid codon to a stop codon, halting protein production.

Transgenic organism

An organism that contains genes from another species.

Speciation

Formation of new species through evolution.

Osteichthyes

Class of fish with bony skeletons (e.g., trout, salmon).

Selective pressure

Environmental factor that influences reproductive success in individuals.

Coevolution

When two or more species evolve in response to each other.

Gradualism

Slow, steady evolutionary change over time.

Okazaki fragment

Short DNA segment synthesized on the lagging strand during replication.

Polymerase Chain Reaction (PCR)

Technique used to amplify specific DNA sequences rapidly.

Central Dogma of Biology

Describes the flow of genetic information: DNA → RNA → Protein.

Habitat isolation

Prezygotic barrier; species live in different environments.

Postzygotic barriers

Barriers that prevent the survival or reproduction of offspring after fertilization.

mRNA (Messenger RNA)

Carries genetic information from DNA to the ribosome.

Chromosomal mutation

A mutation that affects an entire chromosome or large sections of DNA.

RNA polymerase

Enzyme that builds RNA from a DNA template during transcription.

Protein synthesis

The process of building proteins from mRNA instructions (includes transcription and translation).

Convergent evolution

Unrelated species evolve similar traits due to similar environments (e.g., dolphin and shark fins).