Genetic Exam 1 terms

• Consanguinity: A close family relationship between two individuals, such as first cousins.

• Cystic fibrosis: An often fatal recessive genetic disorder associated with abnormal secretions of the exocrine glands.

• Marfan syndrome: An autosomal dominant genetic disorder that affects the skeletal system, the cardiovascular system, and the eyes.

• X-linked: The pattern of inheritance that results from genes located on the X chromosome.

• Y-linked: The pattern of inheritance that results from genes located only on the Y chromosome.

• Hemizygous: A gene present on the X chromosome that is expressed in males in both the recessive and dominant condition.

• Color blindness: Defective color vision caused by reduction or absence of visual pigments. There are three forms: red, green, and blue blindness.

• Muscular dystrophy: A group of genetic diseases associated with progressive degeneration of muscles. Two of these, Duchenne and Becker muscular dystrophy, are inherited as X-linked allelic recessive traits.

• Huntington disease: An autosomal dominant disorder associated with progressive neural degeneration and dementia. Adult onset is followed by death 10 to 15 years after symptoms appear.

• Penetrance: The probability that a disease phenotype will appear when a disease-related genotype is present.

• Expressivity: The range of phenotypes resulting from a given genotype.

• Camptodactyly: A dominant human genetic trait that is expressed as immobile, bent, little fingers.

Gene: The fundamental unit of heredity.

• Dominant trait: The trait expressed in the F₁ (or heterozygous) condition.

• Recessive trait: The trait unexpressed in the F₁, but which is re-expressed in some members of the F₂

• Phenotype: The observable properties of an organism.

• Genotype: The specific genetic constitution of an organism.

• Allele: One of the possible alternative forms of a gene, usually distinguished from other alleles by its phenotypic effects.

• Homozygous: Having identical alleles for one or more genes.

• Heterozygous: Carrying two different alleles for one or more genes.

• Segregation: The separation of members of a gene pair from each other during gamete formation.

• Independent assortment: The random distribution of genes into the gametes during meiosis.

• Genetics: The scientific study of heredity.

• Locus: The position occupied by a gene on a chromosome.

• Pedigree: A diagram listing the members and ancestral relationships in a family; used in the study of human heredity.

• Proband: First affected family member seeking medical attention for a genetic disorder.

• Incomplete dominance: Expression of a phenotype that is intermediate between those of the parents.

• Codominance: Full phenotypic expression of both members of a gene pair in the heterozygous condition.

• Multiple alleles: Genes that have more than two alleles.

• Epistasis: A form of gene interaction in which one gene prevents or masks the expression of a second gene.

• Macromolecules: Large cellular polymers assembled by chemically linking monomers together.

• Carbohydrates: Macromolecules including sugars, glycogen, and starches composed of sugar monomers linked and cross-linked together.

• Lipids: A class of cellular macromolecules including fats and oils that is insoluble in water.

• Proteins: A class of cellular macromolecules composed of amino acid monomers linked together.

• Nucleic acids: A class of cellular macromolecules composed of nucleotide monomers linked together. There are two types of nucleic acids, deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), which differ in the structure of the monomers.

• Molecules: Structures composed of two or more atoms held together by chemical bonds.

• Organelles: Cytoplasmic structures that have specialized functions.

• Endoplasmic reticulum (ER): A system of cytoplasmic membranes arranged into sheets and channels whose function it is to synthesize and transport gene products.

• Ribosomes: Cytoplasmic particles that aid in the production of proteins.

• Golgi complex: Membranous organelles composed of a series of flattened sacs. They sort, modify, and package proteins synthesized in the ER.

• Lysosomes: Membrane-enclosed organelles that contain digestive enzymes.

• Mitochondria (mitochondrion): Membrane-bound organelles, present in the cytoplasm of all eukaryotic cells, which are the sites of energy production within the cells.

• Nucleus: The membrane-bound organelle in eukaryotic cells that contains the chromosomes.

• Nucleolus (nucleoli): A nuclear region that functions in the synthesis of ribosomes.

• Chromatin: The DNA and protein components of chromosomes, visible as clumps or threads in nuclei.

• Chromosomes: The thread-like structures in the nucleus that carry genetic information.

• Sex chromosomes: In humans, the X and Y chromosomes that are involved in sex determination.

• Autosomes: Chromosomes other than the sex chromosomes. In humans, chromosomes 1 to 22 are autosomes.

• Cell cycle: The sequence of events that takes place between successive mitotic divisions.

• Interphase: The period of time in the cell cycle between mitotic divisions.

• Mitosis: Form of cell division that produces two cells, each of which has the same complement of chromosomes as the parent cell.

• Cytokinesis: The process of cytoplasmic division that accompanies cell division.

• Prophase: A stage in mitosis during which the chromosomes become visible and contain sister chromatids joined at the centromere.

• Chromatid: One of the strands of a duplicated chromosome joined by a single centromere to its sister chromatid.

• Centromere: A region of a chromosome to which microtubule fibers attach during cell division. The location of a centromere gives a chromosome its characteristic shape.

• Sister chromatids: Two chromatids joined by a common centromere. Each chromatid carries identical genetic information.

• Metaphase: A stage in mitosis during which the chromosomes move and become arranged near the middle of the cell.

• Anaphase: A stage in mitosis during which the centromeres split and the daughter chromosomes begin to separate.

• Telophase: The last stage of mitosis, during which the chromosomes of the daughter cells decondense and the nucleus re-forms.

• Meiosis: The process of cell division during which one cycle of chromosomal replication is followed by two successive cell divisions to produce four haploid cells.

• Diploid (2n): The condition in which each chromosome is represented twice as a member of a homologous pair.

• Haploid (n): The condition in which each chromosome is represented once in an unpaired condition.

• Homologous chromosomes: Chromosomes that physically associate (pair) during meiosis. Homologous chromosomes have identical gene loci.

• Assortment: The result of meiosis I that puts random combinations of maternal and paternal chromosomes into gametes.

• Crossing over: A process in which chromosomes physically exchange parts.

• Allele: One of the possible alternative forms of a gene, usually distinguished from other alleles by its phenotypic effects.

• Spermatogonia: Mitotically active cells in the gonads of males that give rise to primary spermatocytes.

• Spermatids: The four haploid cells produced by meiotic division of a primary spermatocyte.

• Oogonia: Mitotically active cells in the gonads of females that produce primary oocytes.

• Primary oocyte: The cell produced from oogonia that will begin meiosis during embryogenesis.

• Secondary oocyte: The large cell produced by the first meiotic division.

• Ovum: The haploid cell produced by meiosis that becomes the functional gamete.

• Polar bodies: Cells produced in the first or second meiotic division in female meiosis that contain little cytoplasm and will not function as gametes.

• Translational Medicine: The union of research and medicine that seeks to quickly translate research findings into methods for the diagnosis and treatment of diseases.

• Immunotherapy: A method for treating diseases by stimulating or enhancing an immune response.

• Genetics: The scientific study of heredity.

• Trait: Any observable property of an organism.

• Gene: The fundamental unit of heredity and the basic structural and functional unit of genetics.

• DNA: A helical molecule consisting of two strands of nucleotides that is the primary carrier of genetic information.

• Transmission genetics: The branch of genetics concerned with the mechanisms by which genes are transferred from parent to offspring.

• Pedigree analysis: The construction of family trees and their use to follow the transmission of genetic traits in families. It is the basic method of studying the inheritance of traits in humans.

• Cytogenetics: The branch of genetics that studies the organization and arrangement of genes and chromosomes using the techniques of microscopy.

• Karyotype: A complete set of chromosomes from a cell that has been photographed during cell division and arranged in a standard sequence.

• Molecular genetics: The study of genetic events at the biochemical level.

• Recombinant DNA technology: A series of techniques in which DNA fragments are linked to self-replicating vectors to create recombinant DNA molecules, which are replicated in a host cell.

• Clones: Genetically identical molecules, cells, or organisms all derived from a single ancestor.

• Gene therapy: Procedure in which normal genes are transplanted into humans carrying defective copies as a means of treating genetic diseases.

• Genome: The set of genetic information carried in the DNA of an individual.

• Genomics: The study of the organization, function, and evolution of genomes.

• Population genetics: The branch of genetics that studies inherited variation in populations of individuals and the forces that alter gene frequency.

• Eugenics: The attempt to improve the human species by selective breeding.

• Hereditarianism: The idea that human traits are determined solely by genetic inheritance, ignoring the contribution of the environment. 

• Single nucleotide polymorphism (SNP): Single nucleotide differences between and among individuals in a population or species.

• Haplotype: A set of genetic markers located close together on a single chromosome or chromosome region.

• Genome-wide association study (GWAS): Analysis of genetic variation across an entire genome searching for association between variations and a genome region encoding a specific phenotype.

• Biotechnology: The use of recombinant DNA technology to produce commercial goods and services.