Genetics and DNA

Unit Review Sheet

Facts and Definitions

Lesson 1: The Importance of DNA

• A trait is a characteristic that is genetically determined. Traits are the result of the decoding of DNA.
• Genetics is a branch of biology that deals with heredity and genetic variations.
• Heredity is the transfer of genetically controlled characteristics such as hair color or flower color from one generation to the next in living organisms.
• Variations are differences in traits among individuals within a group of organisms.
• Genes are pieces of genetic information for a specific trait, such as hair color.
• DNA (deoxyribonucleic acid) is a molecule found in all multicellular organisms; DNA contains genetic information. DNA is found in each individual cell (except for red blood, hair, toenail and fingernail cells) and is passed from old cells to new cells.

Lesson 2: Inheritance

• An allele is one of two or more alternative forms of a gene, occupying the same position (locus) on paired (homologous) chromosomes and controlling the same inherited characteristic.
• Inheritance is the transmission of genetically controlled characteristics or qualities from parent to offspring.
• Dominant describes an allele that produces a trait in an organism with only one copy of that allele, although it will also appear with two copies.
• Recessive describes an allele that produces a trait in an organism only when two copies of the allele are present.
• Homozygous describes an organism when it has a gene that has two of the same alleles (versions).
• Heterozygous describes an organism when it has a gene that has two or more different alleles (versions).

Lesson 3: Generations, Probability, and Change

• Probability is the likelihood that an event will occur, expressed as the ratio of the number of favorable outcomes in the set of outcomes divided by the total number of possible outcomes.
• A generation is a single stage in the descent of a family or a group of people, animals, or plants, or the individual members of that stage.
• A genotype is the genetic makeup of an organism.
• A phenotype is how the genotype is expressed in the organism, e.g., blue eyes or brown.
• A Punnett square is a diagram that is used to predict an outcome of a particular cross or breeding.
• A pedigree is the line of ancestors of an individual animal or person, especially a pure-bred animal.

Lesson 4: Reproduction and Change

• Somatic cells are the regular body cells, such as skin cells, muscle cells, and bone cells.
• Gametes are specialized male or female cells with half the normal number of chromosomes; they unite with cells of the opposite sex in the process of sexual reproduction.
• Asexual reproduction is reproduction in which there is no fusion of male and female gametes; only one organism's genetic material is used for reproduction.
• Sexual reproduction is reproduction that involves the union of male and female gametes, each contributing half of the genetic makeup.
• Chromosomes are structures, usually found in pairs in a cell nucleus, that carry the genes that determine gender and the characteristics an organism inherits from its parents.
• Crossing over is the exchange of genetic material between chromosomes that results in recombinant chromosomes.
• Recombinant chromosomes contain a combination of genes not found in either parent.
• Meiosis is a process of cell division during which the nucleus divides into four nuclei, each of which contains half the usual number of chromosomes.

Lesson 5: From Generation to Generation

• Phenotypes, the visible characteristics of an organism, result from the interaction between the organism's genetic make-up and its environment.

Lesson 6: Diversity and Adaptation

• Adaptation is an increase within a population, over time, in inherited characteristics that provide an advantage in a given environment.
• Biodiversity is the range of organisms present in a particular community or ecosystem.
• Competition occurs when organisms vie for the same resources.
• Natural selection is the survival of organisms with traits that fit best with the environment. Organisms with the best genetic make-up and best adaptations are the ones that are most likely to survive, reproduce, and pass on their genes to the next generation.
• Genetic variation involves differences in genomes among members of a species.
• A genome is the genetic information that an organism inherits from its parents, specifically the set of chromosomes and the genes they carry.
• A genetic mutation is a random change in a gene or chromosome resulting in a new trait or characteristic that can be inherited.
• A population is all the organisms of a particular species present in a place.
• A species is a basic biological classification containing individuals that resemble one another and can reproduce together.

Lesson 7: Inheritance and Environment

• Disease is a condition in humans, plants, or animals that results in symptoms and is not the direct result of physical injury.
• Genetic transmission is the transfer of genetic information (in the form of genes) from parents to offspring.
• Biological inheritance is the passing of traits or the predisposition of traits from parent to offspring.
• Incomplete dominance is a form of inheritance in which one allele for a specific trait is not completely dominant over the other allele.

Lesson 8: Cloning

• Cloning is a process that produces a genetically identical copy of something, such as a cell or organism. Cloning can occur naturally (such as plants and bacteria reproducing asexually) or artificially (scientists copying cells or genes, for example).

Final Project: A New Organism

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