Genotype

The genetic makeup of an organism. Examples: DD, Dd, or dd.

Phenotype

The physical trait that is expressed. Examples: brown eyes or blue eyes.

Homozygous

Having two of the same alleles. DD is homozygous dominant and dd is homozygous recessive.

Heterozygous

Having two different alleles. Example: Dd.

Dominant allele

An allele that can be expressed when only one copy is present.

Recessive allele

An allele that is expressed when two recessive copies are present.

Punnett square

A chart used to predict possible genotypes of offspring.

Mendel

Gregor Mendel studied how traits are passed from parents to offspring and is known as the father of genetics.

Asexual reproduction

Reproduction involving only one parent. Offspring are generally genetically identical or very similar to the parent.

Fragmentation

Asexual reproduction where an organism breaks into pieces and a piece can grow into a complete organism.

Fission

Asexual reproduction where an organism divides into two or more parts, producing new organisms.

Vegetative reproduction

Asexual reproduction in plants using specialized structures such as stolons and rhizomes.

Stolon

A long stem or shoot that grows from a parent plant and can develop roots and become a new plant. Example: strawberries.

Rhizome

An underground stem that contains nodes that can produce new growth. Example: aspen trees.

Budding

Asexual reproduction where a small growth called a bud develops on the parent and eventually becomes a new organism. Example: Hydra.

Parthenogenesis

Development of an organism from an unfertilized egg.

Genetic variation

Differences in genetic makeup between individuals in a population.

Mutation

A change in DNA or genetic material.

Beneficial mutation

A mutation that can help an organism survive or reproduce.

Neutral mutation

A mutation that does not have a major effect on an organism.

Harmful mutation

A mutation that negatively affects an organism.

Crossing over

The exchange of pieces of DNA between chromosomes during meiosis. It creates new combinations of genetic information.

Sexual reproduction

Reproduction that combines genetic information from two parents and creates genetic variation.

Autosomes

Chromosomes that contain genes involved in normal body development and function. Humans have 22 pairs.

Sex chromosomes

The chromosome pair involved in determining biological sex. Humans typically have XX or XY.

Meiosis

The process that produces sex cells, such as sperm and eggs, and reduces the chromosome number by half.

Diploid

Having a full set of chromosomes. Human diploid cells have 46 chromosomes and are represented as 2n.

Haploid

Having half the normal number of chromosomes. Human gametes are haploid.

Incomplete dominance

When neither allele completely dominates the other, producing a combination phenotype.

Codominance

When both alleles are expressed at the same time.

Blood type

A, B, AB, and O are the main blood types.

Universal donor

O negative is the universal blood donor.

Universal receiver

AB positive is the universal blood receiver.

Law of Segregation

Mendel's law stating that allele pairs separate during gamete formation, so each gamete receives one allele.

Law of Independent Assortment

Mendel's law stating that different gene pairs can be inherited independently.

DNA

The molecule that contains genetic instructions for building and running an organism.

Double helix

The twisted-ladder shape of DNA.

Deoxyribose

The sugar found in DNA.

DNA bases

Adenine, thymine, cytosine, and guanine.

DNA base pairing

A pairs with T, and C pairs with G.

Gene

A section of DNA that contains instructions.

Protein

A molecule made from amino acids that helps perform functions in cells and the body.

Enzymatic protein

A protein that helps with chemical reactions, including breaking down macromolecules.

Hormonal protein

A protein that helps communicate and regulate processes such as growth and development.

Structural protein

A protein that helps form physical structures in the body.

DNA → RNA → Protein

The basic process by which information in DNA is used to make proteins.

Transcription

The process of copying information from DNA into RNA.

mRNA

Messenger RNA. It carries genetic instructions from DNA to the ribosome.

RNA

Usually single-stranded, contains ribose sugar, and uses uracil instead of thymine.

RNA bases

A, U, C, and G.

Translation

The process of using mRNA to build a protein.

Codon

A group of three RNA bases that helps determine which amino acid is added to a protein.

tRNA

Transfer RNA. It brings amino acids to the ribosome during translation.

Ribosome

The structure that reads mRNA and helps build proteins.

Golgi apparatus

An organelle that can modify, package, and direct proteins to where they need to go.

Gene regulation

The process of controlling which genes are turned on or off and how much they are used.

Cellular differentiation

The process where cells become specialized for different jobs.

Histones

Proteins that DNA wraps around to help organize and tightly pack DNA.

Locus

The location of a specific gene or trait on a chromosome.

Linked genes

Genes located close together on the same chromosome that can often be inherited together.

Gene expression

The process of using information in DNA to make a functional product, usually a protein.

Operon

A section of DNA containing genes and regulatory regions involved in producing a specific protein or group of proteins.

Promoter

The region of DNA where RNA polymerase attaches to begin transcription.

RNA polymerase

An enzyme that attaches to DNA and makes an RNA copy during transcription.

Operator

A regulatory region of DNA where a repressor can attach to control transcription.

Repressor

A protein that can stop or reduce gene transcription.

Enhancer

A DNA region that can increase gene expression.

Silencer

A DNA region that can decrease gene expression.

Activator

A molecule or protein that helps turn gene expression on.

Chromatin

DNA combined with histone proteins. It helps organize and compact DNA.

Cell signaling

The process cells use to communicate with each other through signals.

Lactase

An enzyme that breaks down lactose.

Lactose

The sugar found in dairy products.

Protease

An enzyme that breaks down proteins.

Amylase

An enzyme that breaks down carbohydrates.

Cloning

The process of creating an organism or cell with genetic material that is the same or nearly the same as another organism or cell.

Clone

An organism or cell with genetic material that is the same or nearly the same as another organism or cell.

Stem cell

An unspecialized cell that can develop into specialized cell types.

Differentiated cell

A cell that has become specialized for a specific function.

Undifferentiated cell

A cell that has not yet become specialized.

Cell cycle

The stages a cell goes through as it grows, copies its DNA, and prepares to divide.

Interphase

The part of the cell cycle that includes G1, S, and G2.

G1 phase

The phase when the cell grows, develops, and performs normal functions.

S phase

The phase when DNA is replicated.

G2 phase

The phase when the cell checks copied DNA and prepares for division.

Mitosis

The division of the nucleus and separation of duplicated chromosomes.

PMAT

The order of the four stages of mitosis: Prophase, Metaphase, Anaphase, Telophase.

Prophase

The stage when chromosomes condense, the nuclear envelope breaks down, and spindle structures form.

Metaphase

The stage when chromosomes line up in the middle of the cell.

Anaphase

The stage when sister chromatids are pulled apart to opposite sides of the cell.

Telophase

The stage when chromosomes reach opposite sides and new nuclear envelopes form.

Cytokinesis

The division of the cytoplasm that produces two separate cells.

Sister chromatids

Two identical copies of a replicated chromosome held together by a centromere.

Centromere

The region that holds sister chromatids together.

Chromatin

Loose, extended DNA.

Chromosome

Tightly condensed DNA, especially visible during cell division.

Cleavage furrow

The inward pinching of an animal cell during cytokinesis.

Cell plate

A structure that forms between plant cells during cytokinesis and develops into a new cell wall.

Cell division

Cells divide for growth, repair, replacement of damaged or old cells, and development.