AP Biology Vocabulary #3

Gene

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).

Asexual Reproduction

The generation of offspring from a single parent that occurs without the fusion of gametes, with offspring typically genetically identical to the parent.

Clone

(1) A lineage of genetically identical individuals or cells. (2) An individual that is genetically identical to another individual. (3) To make one or more genetic replicas of an individual or cell.

Sexual Reproduction

A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from both parents via the gametes.

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

Homologous Chromosomes

A pair of chromosomes that possess genes for the same characters at corresponding loci, inherited from each parent.

Sex Chromosomes

A chromosome responsible for determining the sex of an individual.

Autosome

A chromosome that is not directly involved in determining sex.

Haploid Cell

A cell containing only one set of chromosomes (n).

Fertilization

(1) The union of haploid gametes to produce a diploid zygote. (2) The addition of mineral nutrients to the soil.

Gamete

A haploid reproductive cell, such as an egg or sperm, that unites during sexual reproduction.

Zygote

The diploid product of the union of haploid gametes during fertilization.

Diploid Cell

A cell containing two sets of chromosomes (2n), one set inherited from each parent.

Meiosis

A modified type of cell division in sexually reproducing organisms resulting in cells with half the number of chromosome sets as the original cell.

Crossing Over

The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis.

Trait

One of two or more detectable variants in a genetic character.

True-breeding

Referring to organisms that produce offspring of the same variety over many generations of self-pollination.

P Generation

The true-breeding (homozygous) parent individuals from which F1 hybrid offspring are derived.

F1 Generation

The first filial, hybrid (heterozygous) offspring arising from a parental cross.

F2 Generation

The offspring resulting from interbreeding (or self-pollination) of the hybrid F1 generation.

Allele

Any of the alternative versions of a gene that may produce distinguishable phenotypic effects.

Dominant

An allele that is fully expressed in the phenotype of a heterozygote.

Recessive

An allele whose phenotypic effect is not observed in a heterozygote.

Law of Segregation

Mendel's first law stating that the two alleles in a pair segregate into different gametes during gamete formation.

Homozygous

Having two identical alleles for a given gene.

Heterozygous

Having two different alleles for a given gene.

Phenotype

The observable physical and physiological traits of an organism, determined by its genetic makeup.

Genotype

The genetic makeup, or set of alleles, of an organism.

Testcross

Breeding an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype.

Monohybrid

An organism that is heterozygous with respect to a single gene of interest.

Dihybrid

An organism that is heterozygous with respect to two genes of interest.

Law of Independent Assortment

Mendel's second law stating that each pair of alleles segregates independently of each other pair during gamete formation.

Incomplete Dominance

When the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele.

Codominance

When both alleles are exhibited in the heterozygote, affecting the phenotype in distinguishable ways.

Polygenic Inheritance

An additive effect of two or more genes on a single phenotypic character.

Pedigree

A diagram of a family tree showing the occurrence of heritable characters in parents and offspring over generations.

Carrier

An individual who is heterozygous at a given genetic locus for a recessively inherited disorder.

Phenotypic Plasticity

The ability of one genotype to produce more than one phenotype in response to different environments.

Semiconservative Replication

Type of DNA replication in which the replicated double helix consists of one old strand and one newly made strand.

Transcription

The synthesis of RNA using a DNA template.

Translation

The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule.

Gene Expression

The process by which information encoded in DNA directs the synthesis of proteins or RNAs.

Operon

A unit of genetic function found in bacteria, consisting of a promoter, an operator, and a cluster of genes.

Transcription Factor

A regulatory protein that binds to DNA and affects transcription of specific genes.

Epigenetic Inheritance

Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence.

Induction

The process in which one group of embryonic cells influences the development of another.

Differentiation

The process by which a cell or group of cells become specialized in structure and function.

Mutation

A change in the nucleotide sequence of an organism's DNA or in the DNA or RNA of a virus.

Plasmid

A small, circular, double-stranded DNA molecule that carries accessory genes separate from those of a bacterial chromosome.

Recombinant DNA

A DNA molecule made in vitro with segments from different sources.

Restriction Enzyme

An endonuclease that recognizes and cuts DNA molecules foreign to a bacterium.

Restriction Site

A specific sequence on a DNA strand recognized and cut by a restriction enzyme.

Restriction Fragment

A DNA segment that results from the cutting of DNA by a restriction enzyme.

Gel Electrophoresis

A technique for separating nucleic acids or proteins based on their size and electrical charge.

Capsid

The protein shell that encloses a viral genome.

Reverse Transcriptase

An enzyme that uses RNA as a template for DNA synthesis in certain viruses.

Lytic Cycle

A type of phage replicative cycle resulting in the release of new phages by lysis of the host cell.

Lysogenic Cycle

A type of phage replicative cycle where the viral genome becomes incorporated into the bacterial host chromosome.

Conjugation

The direct transfer of DNA between two prokaryotic cells that are temporarily joined.

Transformation

A change in genotype and phenotype due to the assimilation of external DNA by a cell.

Transduction

A process in which phages carry bacterial DNA from one bacterial cell to another.