Heredity Midterm

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Genetics

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The scientific study of heredity.

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Trait

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Any observable property of an organism

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DNA

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A helical molecule consisting of two strands of nucleotides that is the primary carrier of genetic information

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Transmission genetics

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

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Pedigree analysis

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* 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.

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Cytogenetics

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

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Karyotype

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

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Molecular genetics

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* The study of genetic events at the biochemical level.

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Recombinant DNA technology

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* 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.

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Clones

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

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Gene therapy

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

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Genome

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* The set of genetic information carried in the DNA of an individual.

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Genomics

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The study of the organization, function, and evolution of genomes.

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Population genetics

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

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Eugenics:

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

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Hereditarianism:

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

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Single nucleotide polymorphism (SNP):

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* Single nucleotide differences between and among individuals in a population or species.

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Biotechnology

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* The use of recombinant DNA technology to produce commercial goods and services.

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Macromolecules:

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Large cellular polymers assembled by chemically linking monomers together.

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Carbohydrates:

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Macromolecules including sugars, glycogen, and starches composed of sugar monomers linked and cross-linked together

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Lipids:

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

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Proteins:

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

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Nucleic acids:

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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

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Molecules

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

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Organelles

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Cytoplasmic structures that have specialized functions.

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Endoplasmic reticulum (ER):

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A system of cytoplasmic membranes arranged into sheets and channels whose function it is to synthesize and transport gene products.

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Ribosomes

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Cytoplasmic particles that aid in the production of proteins.

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Lysosomes:

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Membrane-enclosed organelles that contain digestive enzymes

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Mitochondria (mitochondrion)

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Membrane-bound organelles, present in the cytoplasm of all eukaryotic cells, which are the sites of energy production within the cells.

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Nucleus:

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

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Nucleolus (nucleoli):

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A nuclear region that functions in the synthesis of ribosomes.

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Chromatin:

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

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Chromosomes:

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

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Sex chromosomes

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

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Golgi complex

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

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Autosomes

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

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Genes:

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: The fundamental units of heredity.

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Cell cycle

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

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Mitosis:

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

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Cytokinesis:

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The process of cytoplasmic division that accompanies cell division.

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Diploid (2n):

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The condition in which each chromosome is represented twice as a member of a homologous pair.

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Haploid (n):

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The condition in which each chromosome is represented once in an unpaired condition

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Homologous chromosomes

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

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Assortment:

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

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Crossing over

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A process in which chromosomes physically exchange parts.

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Spermatogonia:

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

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Oogonia

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

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Genes:

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: The fundamental units of heredity.

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Recessive trait:

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The trait unexpressed in the F1, but which is re-expressed in some members of the F2 generation.

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Dominant trait

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

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Phenotype:

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The observable properties of an organism.

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Genotype

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The specific genetic constitution of an organism.

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Segregation

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

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Allele:

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

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Homozygous

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Having identical alleles for one or more genes.

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Heterozygous

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Carrying two different alleles for one or more genes.

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Independent assortment:

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The random distribution of genes into the gametes during meiosis.

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Genetics:

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The scientific study of heredity.

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Locus:

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The position occupied by a gene on a chromosome.

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Pedigree construction

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Use of family history to determine how a trait is inherited, and to determine risk factors for family members

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Pedigree

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

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Proband:

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

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Incomplete dominance

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Expression of a phenotype that is intermediate between those of the parents.

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Codominance:

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Full phenotypic expression of both members of a gene pair in the heterozygous condition

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Multiple alleles

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Genes that have more than two alleles.

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Cystic fibrosis

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

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Sickle cell anemia

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: A recessive genetic disorder associated with an abnormal type of hemoglobin, a blood transport protein

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Marfan syndrome

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

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X-linked:

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The pattern of inheritance that results from genes located on the X chromosome.

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Y-linked

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

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Color blindness

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

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Muscular dystrophy:

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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.

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Huntington disease

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An autosomal dominant genetic disorder associated with progressive neural degeneration and characterized by involuntary movements of the limbs, dementia, and death within 15 years of onset. Symptoms appear between 30 and 50 years of age.

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Camptodactyly

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

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Polygenic traits:

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Traits controlled by two or more genes.

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Multifactorial traits

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: Traits that result from the interaction of one or more environmental factors and two or more genes.

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Complex traits:

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Traits controlled by multiple genes and the interaction of environmental factors where the contribution of genes and environment are undefined.

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Heritability:

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An expression of how much of the observed variation in a phenotype is due to differences in genotype.

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Genetic variance

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The phenotypic variance of a trait in a population that is attributed to genotypic differences.

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Environmental variance

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The phenotypic variance of a trait in a population that is attributed to differences in the environment

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Monozygotic (MZ) twins

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Twins derived from a single fertilization event involving one egg and one sperm; such twins are genetically identical.

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Dizygotic (DZ) twins:

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Twins derived from two separate and nearly simultaneous fertilization events, each involving one egg and one sperm. Such twins share, on average, 50 percent of their genes.

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Concordance:

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: Agreement between traits exhibited by both twins.

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Leptin

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: A hormone produced by fat cells that signals the brain and ovary. As fat levels become depleted, secretion of leptin slows and eventually stops.

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Essential hypertension

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: Elevated blood pressure, consistently above 140/90mm Hg.

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Familial hypercholesterolemia (FH):

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): Autosomal dominant disorder with defective or absent LDL receptors. Affected individuals are at increased risk for cardiovascular

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Intelligence quotient (IQ):

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A score derived from standardized tests that is calculated by dividing the individual's mental age (determined by the test) by his or her chronologic age, and multiplying the quotient by 100.

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Sex chromosomes:

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: Chromosomes involved in sex determination. In humans, the X and y chromosomes are the sex chromosomes

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Autosomes:

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

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Karyotype

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The chromosomal complement of a cell line or person, photographed at metaphase and arranged in a standard sequence.

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Amniocentesis

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Method of sampling the fluid surrounding the developing fetus by the insertion of a hollow needle and the withdrawal of suspended fetal cells and fluid. Used in the diagnosis of fetal genetic and developmental disorders. Usually performed in the 16th week of pregnancy.

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Chorionic villus sampling (CVS):

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Method of sampling fetal chorionic cells by insertion of a catheter through the vagina into the uterus. Used in the diagnosis of biochemical and cytogenetic defects in the embryo. Usually performed in the eighth or ninth week of pregnancy.

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Polyploidy

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A chromosome number that is a multiple of the normal haploid chromosome set.

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Aneuploidy

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A chromosome number that is not an exact multiple of the haploid set.

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Monosomy:

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A condition in which one member of a chromosomal pair is missing; having one less than the diploid number (2n - 1)

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Trisomy:

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A condition in which one chromosome is present in three copies, whereas all others are diploid; having one more than the diploid number (2n + 1)

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Triploidy:

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A chromosome number that is three times the haploid number; having three copies of all autosomes and three sex chromosomes

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Tetraploidy:

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A chromosome number that is four times the haploid number; having four copies of all autosomes and four sex chromosomes.

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Nondisjunction

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The failure of homologous chromosomes to properly separate during meiosis or mitosis.

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Trisomy 21:

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Aneuploidy involving the presence of an extra copy of chromosome 21, resulting in Down syndrome

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Turner syndrome:

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A monosomy of the X chromosome (45,X) that results in female sterility.

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Klinefelter syndrome

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Aneuploidy of the sex chromosomes involving XXY chromosome constitution.

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XYY syndrome:

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: Aneuploidy of the sex chromosomes involving XYY chromosome constitution.

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Deletion:

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Chromosomal aberration in which a segment of a chromosome is deleted or missing.

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Duplication:

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Chromosomal aberration in which a segment of a chromosome is repeated and therefore present in more than one copy within the chromosome.

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Translocation:

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Chromosomal aberration in which a chromosome segment is transferred to another, non-homologous chromosome.

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Inversion:

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Chromosomal aberration in which the order of a chromosome segment is reversed.

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Fragile X:

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An X chromosome that carries a non-staining gap or break at band q27. This is associated with mental retardation in males.

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Zygote

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The fertilized egg that develops into a new individual.

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Oocyte

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: The female gamete.

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Gametes:

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Unfertilized germ cells.

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Oogenesis:

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The process of oocyte production

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Oogonia:

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Mitotically active cells that produce primary oocytes.

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Fertilization

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: The fusion of two gametes to produce a zygote.

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Teratogen

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Any physical or chemical agent that brings about an increase in congenital malformations.

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Fetal alcohol syndrome (FAS):

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A constellation of birth defects caused by maternal alcohol consumption during pregnancy.

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Sex ratio

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The proportion of males to females in any group.

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Pseudohermaphroditism:

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An autosomal genetic condition that causes XY individuals to develop the phenotypic sex of females.

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Dosage compensation

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A mechanism that regulates the expression of sex-linked gene products.

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Sex-influenced traits

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Traits controlled by autosomal genes that are usually dominant in one sex but recessive in the other sex

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Pattern baldness:

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A sex influenced trait that acts like an autosomal dominant trait in males and an autosomal recessive trait in females.

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Sex-limited genes

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: Loci that produce a phenotype that is produced in only one sex.

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Imprinting:

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A phenomenon in which expression of a gene depends on whether it is inherited from the mother or the father.

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Transformation:

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The process of transferring genetic information between cells by means of DNA molecules.

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Transformation:

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The process of transferring genetic information between cells by means of DNA molecules.

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Deoxyribonucleic acid (DNA):

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A molecule consisting of antiparallel strands of polynucleotides that is the primary carrier of genetic information.

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Ribonucleic acid (RNA):

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A nucleic acid molecule that contains the pyrimidine uracil and the sugar ribose. The several forms of RNA function in gene expression.

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Nucleotide

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: The basic building block of DNA and RNA. Each nucleotide consists of a base, a phosphate, and a sugar

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Adenine and guanine

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Nitrogen-containing purine bases found in nucleic acids.

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Thymine, uracil, and cytosine

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Nitrogen-containing pyrimidine bases found in nucleic acids.

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Ribose and deoxyribose:

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Pentose sugars found in nucleic acids. Deoxyribose is found in DNA, ribose in RNA.